Article

Attachment of Salmonella spp. and Listeria monocytogenes to stainless steel, rubber and polytetrafluorehtylene: The influence of free energy and the effect of commercial sanitizers

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Abstract

Bacteria and material surfaces were characterized with respect to their hydrophobicity and surface free energy using the contact angle method. Salmonella strains showed higher hydrophobicity and lower surface free energies than Listeria monocytogenes strains. Polytetrafluorethylene was the most hydrophobic material (and had the lowest surface free energy), followed by rubber and stainless steel. Bacteria attached in higher numbers to the more hydrophobic materials. Bacterial adherence could not be correlated with surface free energies or contact angles of bacteria, although L. monocytogenes strains attached in higher numbers than Salmonella strains to all of the materials tested. The cleaning of materials with commercial sanitizers resulted in a decrease of their contact angles (and an increase of their surface free energies), accompanied by a reduction in the number of adhered bacteria in comparison with the standard conditions. The degree of reduction in bacterial adherence varied with the bacteria, the substrate material and the sanitizer tested. Quaternary ammonium compounds were more effective against Salmonella attachment than L. monocytogenes attachment. Diethylenetriamine showed similar efficacy against attachment of both bacteria. Polytetrafluorethylene showed the greatest reduction in attachment after being washed with commercial sanitizers. It is concluded that stainless steel is less adherent than rubber or polytetrafluorethylene and should be preferred in the food industry when possible. On the other hand, polytetrafluorethylene seems to be more easily sanitized. Since effectiveness of sanitizers in the reduction of bacterial adherence was dependent upon the bacteria and the materials studied, the use of mixtures of sanitizers would help to control bacterial adherence in the food industry.

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... Attachment after 96-h on nylon and wood was similar to 24-h nylon, while 96-h HDPE and 24-wood exhibited a similar degree of attachment. Similarly to previous research, attachment was significantly impacted by surface type [9,20,21]. and incubation time [18,22]. Salmonella isolates from poultry sources attached greater on polycarbonate surfaces compared to stainless steel [23].Another study) [24] found that the initial surface coverage of Salmonella was dependent on stainless steel finish and increased over a 5-day incubation period. ...
... Deionized water and formamide were used as reference liquids to elucidate the physiochemical characteristics of biofilms (Table 1). Previous researchers have suggested that pathogen attachment is favored on hydrophobic surfaces [21]. Salmonella attachment and material hydrophobicity was positively correlated between select materials but they were not able to correlate attachment and hydrophobicity of all materials [9]. ...
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... Among the common sites for the presence of Salmonella in food manufacturing areas are floors, drains, pipelines, walls, conveyors, and racks. Furthermore, bacteria can attach to surfaces such as plastic, glass, stainless steel, or rubber (Sinde & Carballo, 2000;Agarwal et al., 2011;Nillian et al., 2016). ...
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... attach differently to the same surface, with attachment varying according to surface properties as well as the bacteria's characteristics. According to a study by Sinde & Carballo (2000), L. monocytogenes and Salmonella spp. adhesion to various surfaces differed greatly. ...
... strains being more hydrophobic and having lower surface free energy than L. monocytogenes strains. Additionally, they discovered that, compared to Salmonella spp., L. monocytogenes adhered to all surfaces in higher quantities [55]. The attachment of Salmonella spp. ...
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... It is one of the most widely produced plastics worldwide (Omnexus, 2022). This surface is routinely used for food preparation in industrial plants, commercial establishments, and domestic environments (Carpentier, 1997;Sinde and Carballo, 2000). Stainless steel is also one of the most commonly used materials in food-processing plants and domestic environments. ...
... According to Rosenberg (1981), hydrophobic interactions play a significant role in bacterial adherence to surfaces, and a strong correlation between cell surface hydrophobicity and bacterial affinity for polymers has been described. Previous studies have shown that bacterial adhesion to hydrophobic surfaces is stronger than that to hydrophilic surfaces (Sinde and Carballo, 2000;Rodrigues et al., 2009;Tondo et al., 2010;Steenackers et al., 2012;Dantas et al., 2018;Obe et al., 2022). However, other authors have suggested that the hydrophobic nature of the surfaces is not a determinant of bacterial adhesion as hydrophilic surfaces, such as stainless steel and glass, similarly promote bacterial adhesion and biofilm formation (Chia et al., 2009;Nguyen et al., 2014;Oliveira et al., 2014;Cai et al., 2019). ...
Article
Poultry products are recognized as the main source of Salmonella and Campylobacter jejuni infections in humans, while avian pathogenic Escherichia coli may have zoonotic potential and can be transmitted from chicken meat to humans. Biofilm formation contributes to their spread through the food chain. This study aimed to compare the adhesion of Salmonella Enteritidis, E. coli, and C. jejuni strains isolated from poultry, food implicated in outbreaks, and poultry slaughterhouses on three surfaces widely used in poultry production (polystyrene, stainless steel, and polyethylene). S. Enteritidis and E. coli adhesion on the three surfaces tested were not significantly different (p > 0.05). Interestingly, the number of C. jejuni cells on stainless steel (4.51-4.67 log10 CFU/cm.-2) was significantly higher (p = 0.0004) than that on polystyrene (3.80-4.25 log10 CFU/cm.-2), but similar (p > 0.05) to that on polyethylene (4.03-4.36 log10 CFU/cm.-2). However, C. jejuni adhesion was significantly lower (p < 0.05) than S. Enteritidis and E. coli adhesion, regardless of the surface evaluated. In addition, scanning electron microscopy analyses have shown an increased irregularity of the stainless steel surface when compared to polyethylene and polystyrene. These irregularities form small spaces ideal for microbial adhesion.
... Attachment is the primary process in biofilm formation and density of biofilm is depends on the surface [20]. Biofoul- ing activity of the Bacillus sp DR4 isolated from ship hull and the maximum optical density 0.596 by Microtitre plate assay method [21]. The attachment of Salmonella sp and Listeria monocytogenes to stainless steel, rubber and poly tetra fluroethylene [21]. ...
... Biofoul- ing activity of the Bacillus sp DR4 isolated from ship hull and the maximum optical density 0.596 by Microtitre plate assay method [21]. The attachment of Salmonella sp and Listeria monocytogenes to stainless steel, rubber and poly tetra fluroethylene [21]. Stainless steel and glass surfaces more suitable for the adherence of Listeria monocytogenes by microtitre plate assay method [22]. ...
... The stronger biofilms on polyurethane surfaces may be related to its greater hydrophobicity than stainless steel (Donlan, 2002). It has been hypothesized that as bacteria cells irreversibly attach to solid surfaces, hydrophobic surfaces may have less electrostatic repulsive forces (Loosecht et al., 1987;Sinde and Carballo, 2000;Donlan, 2002). Other bacteria such as Salmonella and Listeria have also been found to more readily attach and form biofilms on surfaces that are more hydrophobic (Sinde and Carballo, 2000;Donlan, 2002). ...
... It has been hypothesized that as bacteria cells irreversibly attach to solid surfaces, hydrophobic surfaces may have less electrostatic repulsive forces (Loosecht et al., 1987;Sinde and Carballo, 2000;Donlan, 2002). Other bacteria such as Salmonella and Listeria have also been found to more readily attach and form biofilms on surfaces that are more hydrophobic (Sinde and Carballo, 2000;Donlan, 2002). Apart from beef contamination, the different food contact surfaces also affected O103:H2 recovery from 60 days dry biofilms (Table 5), with O103:H2 being more readily recovered from multispecies on TPU than SS at both 10 and 25 • C. A similar result has been reported by Adator et al. (2018), as recovery rates from STECs biofilms were higher on polystyrene than SS (Adator et al., 2018). ...
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... Polyvinyl chloride, ceramic tiles, and stainless steel are common hospital surfaces. Properties such as porosity, hydrophobicity, and free energy of the surface determine how microorganisms adhere and the potential for biofilm formation [27,28]. According to Lagha et al., stainless steel can support biofilm formation and cross-contamination, while materials like ceramics or PVC can also be sources of disease transmission from inanimate surfaces [29]. ...
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Nosocomial infections negatively affect the results obtained from healthcare services. Healthcare-associated infections (HAIs) are most common in patients in intensive care units (ICUs) and immunosuppressed patients. The World Health Organization estimates that HAIs affect hundreds of millions of patients each year, causing major economic losses. Many national health organizations continue to implement precautions to reduce the incidence of hospital infections. Many studies have been conducted on the contamination of frequently used surfaces in hospitals with various microorganisms and their role in causing HAIs. Bacillus subtilis (B. subtilis) is a Gram-positive bacillus. The literature reports that bacillus species can adhere to surfaces through their spore structures. It has been noted that they can survive for approximately four weeks in environments without food, can be transmitted to patients from contaminated surfaces, and can cause infection depending on the number of spores. In numerous studies, B. subtilis has been isolated from various samples including blood, cerebrospinal fluid, liver and spleen abscesses, and vitreous fluid. It is important to recognize that these bacteria may be not only contaminants but also pathogenic microorganisms that can cause HAIs. Understanding the correlation between B. subtilis and HAI will significantly benefit healthcare services.
... coli) biofilms developed faster when cultured in low-nutrient media by increasing cell adhesion on surfaces [30] Irreversible attachment The transition from reversible to irreversible attachment marks a subtle but crucial shift from weak interactions to permanent binding mediated by EPS [27]. At this stage, biofilm removal becomes challenging and requires strong shear forces or the introduction of chemical agents (such as enzymes, detergents, surfactants, and sanitizers) or heat treatments [31][32][33]. The EPS matrix was shown to facilitate the formation of microcolonies and enhance biofilm maturation by promoting cell-to-cell adhesion and providing structural stability [34,35]. ...
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... Listeria monocytogenes, Staphylococcus sciuri, Pseudomonas putida, and Comamonas sp., all posed a greater risk of beef contamination when they were associated with TPU as compared to SS (Midelet & Carpentier, 2002). The higher contamination from biofilms on TPU has been attributed to its higher hydrophobicity as compared to SS, while previous studies demonstrated bacteria such as Salmonella and Listeria more readily formed biofilms on higher hydrophobic surfaces (Donlan, 2002;Sinde & Carballo, 2000). Consequently, biofilms are more likely to form on TPU than SS, and once formed, bacteria sloughing from biofilms on TPU may have a higher chance of contaminating beef (Figure 1). ...
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... The efficiency of bacteriophage when applied in the absence of a food matrix was 1.18 folds higher. The presence of food matrices on food-contacting surfaces can be a considerable concern for the spreading of foodborne pathogens since it is a suitable matrix for bacteria to attach, accumulate, and propagate on surfaces, and finally be a source of cross-contamination of food products [194,195]. The study by Chaitiemwong et al. (1996) investigated the effect of food matrix and grooves on the surface of stainless steel on the efficiency of applying bacteriophage to biofilm-forming pathogens. ...
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... Therefore, implementing an appropriate disinfection regimen is crucial to prevent biofilm maturation and the accumulation of substances that could serve as nutrients for their growth [41]. It is important to note that the effectiveness of disinfectants significantly decreases when surfaces are contaminated with debris or food particles [42]. ...
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... Through this matrix, the adherent microbial cells form a complex with the surface and become protected from environmental influences (Bayoudh et al. 2006;Garrett et al. 2008;Palmer et al. 2007). While reversible adhesion removes bacteria by minimal force, irreversible adherent cells can only be removed by strong mechanical forces, chemical agents or heat (Chmielewski and Frank 2006;Sinde and Carballo 2000). The incomplete disruption of adhesion means that adherent cells can persist even after cleaning and disinfection and consequently pose a serious risk to the food industry through cross-contamination. ...
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... These tools and equipment are often designed and/or built by the farm to support farming activities, not necessarily with consideration to hygienic management and food safety. While there have been many studies on the efficacy of sanitizers on "standard" food contact surface materials (7,14,16), there is limited information on the effectiveness of cleaning and sanitizing practices for more complex surfaces found in produce operations (e.g., wood, rubber, canvas). From our survey data, plastic was the most common produce contact material reported across all surface categories, followed by stainless steel (Fig. 1A). ...
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... The PLA cutting boards employed in the preparation of uncooked foods are highly sensitive to cross-contamination (Stepanovic et al. 2004;Nahar et al. 2021). Additionally, PLA is more susceptible to adhesion compared to glass and SS surfaces (Sinde and Carballo 2000). In order to avoid the spread of salmonella contamination, PLA cutting boards should not be used for food preparation. ...
Article
Salmonella is a food-borne microorganism that is also a zoonotic bacterial hazard in the food sector. This study determined how well a mixed culture of Salmonella Kentucky formed biofilms on plastic (PLA), silicon rubber (SR), rubber gloves (RG), chicken skin and eggshell surfaces. In vitro interactions between the histone deacetylase inhibitor-vorinostat (SAHA)-and S. enterica serotype Kentucky were examined utilizing biofilms. The minimum inhibitory concentration (MIC) of SAHA was 120 µg mL-1. The addition of sub-MIC (60 µg mL-1) of SAHA decreased biofilm formation for 24 h on PLA, SR, RG, Chicken skin, and eggshell by 3.98, 3.84, 4.11, 2.86 and 3.01 log (p < 0.05), respectively. In addition, the initial rate of bacterial biofilm formation was higher on chicken skin than on other surfaces, but the inhibitory effect was reduced. Consistent with this conclusion, virulence genes expression (avrA, rpoS and hilA) and quorum-sensing (QS) gene (luxS) was considerably downregulated at sub-MIC of SAHA. SAHA has potential as an anti-biofilm agent against S. enterica serotype Kentucky biofilm, mostly by inhibiting virulence and quorum-sensing gene expression, proving the histone deacetylase inhibitor could be used to control food-borne biofilms in the food industry.
... Notably higher level of biofilm formation, regarding all tested strains, was recorded for hydrophobic surface, i.e. polystyrene plate in comparison to hydrophilic one (stainless steel). Similar to our results, the research of Sinde and Carballo (2000) found that different strains of L. monocytogenes are more successful in attaching to hydrophobic surfaces than the hydrophilic ones. Favoring our results is also another study in which a dozen of L. monocytogenes isolates expressed greater ability of biofilm formation on polystyrene compared to stainless steel (Poimenidou et al., 2016). ...
... Polymers, including polyethylene, are widely used in the food industry owing to their attractive characteristics [4]. It is routinely used for food preparation in industrial plants, commercial establishments, and domestic environments [14,48]. In this study, S. Heidelberg strains were able to produce biofilms on stainless steel and polyethylene and bacterial counts ranged from 6.66 to 7.54 log 10 CFU cm −2 . ...
Article
Owing to its antimicrobial activity, electrochemically activated water (ECAW) is a potential alternative to chemical disinfectants for eliminating foodborne pathogens, including Salmonella Heidelberg, from food processing facilities. However, their antibiofilm activity remains unclear. This study aimed to evaluate the antibiofilm activity of ECAW against S. Heidel-berg biofilms formed on stainless steel and polyethylene and to determine its corrosive capacity. ECAW (200 ppm) and a broad-spectrum disinfectant (0.2%) were tested for their antibiofilm activity against S. Heidelberg at 25 °C and 37 °C after 10 and 20 min of contact with stainless steel and polyethylene. Potentiostatic polarization tests were performed to compare the corrosive capacity of both compounds. Both compounds were effective in removing S. Heidelberg biofilms. Bacterial counts were significantly lower with ECAW than with disinfectant in polyethylene, regardless the time of contact. The time of contact and the surface significantly influenced the bacterial counts of S. Heidelberg. Temperature was not an important factor affecting the antibiofilm activities of the compounds. ECAW was less corrosive than the disinfectant. ECAW demonstrated a similar or even superior effect in the control of S. Heidelberg biofilms, when compared to disinfectants, reducing bacterial counts by up to 5 log 10 CFU cm −2. The corrosion of stainless steel with ECAW was similar to that of commercial disinfectants. This technology is a possible alternative for controlling S. Heidelberg in the food production chain.
... The major contact surfaces in hospitals are plastic (polyvinyl or polypropylene) surfaces, ceramic tiles and stainless-steel surfaces. These pathogens survive under hospital conditions depending on the porosity, free surface, hydrophobicity, adhesion and biofilm formation ability (Sinde and Carballo 2000;Donlan 2001Donlan , 2002. It is also reported that stainless steel promotes easy formation of biofilm and plastic surfaces can act as a source of disease transmission from inanimate surfaces (Lagha et al. 2015). ...
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Methicillin resistant Staphylococcus aureus (MRSA) infections have increased at an alarming rate, recently. In India, stubble burning and air pollution due to the burning of agricultural and forest residues have also increased over the past decade causing environmental and health hazards. This work evaluates the anti-biofilm property of the aqueous phase obtained from pyrolysis of wheat straw (WS AQ) and pine cone (PC AQ) against an MRSA isolate. The WS AQ and PC AQ compositions were determined by GC-MS analysis. The minimum inhibitory concentration was found to be 8% (v v-1) and 5% (v v-1) for WS AQ and PC AQ, respectively. The eradication of biofilms was performed on hospital contact surfaces namely, stainless steel and polypropylene and found to be 51% and 52% for WS AQ and PC AQ, respectively. Compounds identified from the aqueous phase of WS and PC docked against AgrA protein showed good binding scores.
... The glass and plastic substrata were assumed to the hydrophilic and hydrophobic materials, respectively (Sinde and Carballo 2000). Bacterial cell surface hydrophobicity impacts their attachment to the surfaces (Giaouris et al. 2008). ...
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The prevention of biofilm formation plays a pivotal role in managing Helicobacter pylori inside the body and the environment. This study showed in vitro potentials of two recently isolated probiotic strains, Bacillus sp. 1630F and Enterococcus sp. 7C37, to form biofilm and combat H. pylori attachment to the abiotic and biotic surfaces. Lactobacillus casei and Bifidobacterium bifidum were used as the reference probiotics. The biofilm rates were the highest in the solid–liquid interface for Lactobacillus and Bifidobacterium and the air–liquid interface for Bacillus and Enterococcus. The highest tolerances to the environmental conditions were observed during the biofilm formations of Enterococcus and Bifidobacterium (pH), Enterococcus and Bacillus (bile), and Bifidobacterium and Lactobacillus (NaCl) on the polystyrene and glass substratum, respectively. Biofilms occurred more quickly by Bacillus and Enterococcus strains than reference strains on the polystyrene and glass substratum, respectively. Enterococcus (competition) and Bacillus (exclusion) achieved the most inhibition of H. pylori biofilm formations on the polystyrene and AGS cells, respectively. Expression of luxS was promoted by Bacillus (exclusion, 3.2 fold) and Enterococcus (competition, 2.0 fold). Expression of ropD was decreased when H. pylori biofilm was excluded by Bacillus (0.4 fold) and Enterococcus (0.2 fold) cells. This study demonstrated the ability of Bacillus and Enterococcus probiotic bacteria to form biofilm and combat H. pylori biofilm formation.
... Biofilm formation on the surface of plastic litters Biofilm development was clearly visible on the plastic litters. Previous works have demonstrated that microorganisms stick to surfaces that are more hydrophobic such as plastic [42,43]. This may be one reason for the capacity of these bacteria to build biofilm in large quantities on plastic surface, as adhesion is the initial stage in the intricate process of biofilm development [44]. ...
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The accumulation of plastic litter in the marine environment is a growing ecological concern. Microorganisms can create a biofilm on the surface of plastic litters making them more hazardous. Although plastics are difficult to biodegrade, they can act as substrate for microorganism attachment. To investigate this problem, biofilm coated plastic litters such as covers, films and ropes were collected randomly from Muthunagar and Inigonagar in Tuticorin coastal areas and analysed using FTIR-ATR. The spectra obtained demonstrate the presence of Polyethylene (PE), Polypropylene (PP), Polystyrene (PS) and Polyamide (PA). The concentration of biofilm formed on the surface of plastics is higher in Inigonagar compared to Muthunagar coastal area. Investigations were also conducted into the bacterial development on the plastic surface and in the surrounding water and sediment. Several bacterial communities including human pathogens namely Faecal coliform, E. coli, Salmonella sp., Streptococcus sp., Staphylococcus sp., Pseudomonas sp., Bacillus sp., Klebsiella sp., and Vibrio sp. were found to be associated with the collected plastic litters. We confirmed the weathering of plastic litters by carbonyl and vinyl peaks formation. According to the Carbonyl Index values plastic litters collected from Inigonagar exhibit higher degree of degradation compared to Muthunagar coastal areas. The present study could provide significant baseline information for both plastic pollution and biofilm composition in Muthunagar and Inigonagar coastal areas.
... Surfaces used in poultry production include polyethylene, stainless steel, polypropylene, polyurethane, silicone, and glass [29]. Polyethylene is routinely used during food preparation in industrial plants and is also present in poultry farms, including in transportation crates [30,31]. The ability of Salmonella to produce biofilms on polyethylene has been previously described [11]. ...
Article
Salmonella enterica serotype Enteritidis is one of the main pathogens associated with foodborne illnesses worldwide. Biofilm formation plays a significant role in the persistence of pathogens in food production environments. Owing to an increase in antimicrobial resistance, there is a growing need to identify alternative methods to control pathogenic microorganisms in poultry environments. Thus, this study aimed to synthesize silver nanoparticles (AgNPs) and evaluate their antibiofilm activity against poultry-origin Salmonella Enteritidis in comparison to a chemical disinfectant. AgNPs were synthesized, characterized, and tested for their minimum inhibitory concentration, minimum bactericidal concentration, and antibiofilm activity against S. Enteritidis strains on polyethylene surfaces. The synthesized AgNPs, dispersed in a liquid medium, were spherical in shape with a mean diameter of 6.2 nm. AgNPs exhibited concentration-dependent bactericidal action. The bacterial reduction was significantly higher with AgNPs (3.91 log10 CFU \bullet cm−2) than that with sanitizer (2.57 log10 CFU ∙ cm−2). Regarding the time of contact, the bacterial count after a contact time of 30 min was significantly lower than that after 10 min. The AgNPs exhibited antimicrobial and antibiofilm activity for the removal of biofilms produced by S. Enteritidis, demonstrating its potential as an alternative antimicrobial agent. The bactericidal mechanisms of AgNPs are complex; hence, the risk of bacterial resistance is minimal, making nanoparticles a potential alternative for microbial control in the poultry chain.
... Thus, holding seafood in HDPE for more than three days and biofilm already developed in pipelines of the seafood industry may contaminate seafood with potentially strong biofilm forming Salmonella. Even though plastic is hydrophobic in nature, Salmonella biofilms adhere easily to plastic surfaces (Sinde and Carballo, 2000). The results of the present study confirm with the previous findings that Salmonella produces strong biofilms on plastic surfaces, making cell adhesion easier than other materials (Joseph et al., 2001). ...
Article
The prevalence of biofilm forming Salmonella on different seafood contact surfaces was investigated. Out of 384 swab samples, 16.14 % and 1 % were confirmed biochemically and molecularly as Salmonella respectively. One out of four isolates was from the boat deck, and three were from the seafood processing plant. Salmonella was more prevalent in January, June, and September months. Different assays investigated the biofilm forming ability of isolates. Two out of four isolates have shown strong biofilms, and the others were moderate biofilm formers by microtitre plate assay. In the CRA assay, three isolates showed ‘rdar’ morphotype, and one showed ‘bdar’ morphotype. All isolates were positive for gcpA gene (~1700 bp), a critical gene found in Salmonella biofilms. The microbial load of Salmonella biofilms on different contact surfaces were determined, stainless steel and HDPE were found prone to biofilms. With this, a suitable mechanism shall be formulated to control the biofilms of Salmonella.
... This might explain the differences in the number of attached cells detected. Previous studies [42,44,45] show higher attachment and/or biofilm formation onto SS than rubber and/or plasticwhile other studies show the contrary [25,[46][47][48][49]. Furthermore, similar biofilm formation on PVC, PE, and SS surfaces was also reported by Zacheus, et al. [50]. ...
Article
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Biofilms are highly resistant to external forces, especially chemicals. Hence, alternative control strategies, like antimicrobial substances, are forced. Antimicrobial surfaces can inhibit and reduce microbial adhesion to surfaces, preventing biofilm formation. Thus, this research aimed to investigate the bacterial attachment and biofilm formation on different sealants and stainless steel (SS) surfaces with or without antimicrobials on two Gram-positive biofilm forming bacterial strains. Antimicrobial surfaces were either incorporated or coated with anti-microbial, -fungal or/and bactericidal agents. Attachment (after 3 h) and early-stage biofilm formation (after 48 h) of Staphylococcus capitis (S. capitis) and Microbacterium lacticum (M. lacticum) onto different surfaces were assessed using the plate count method. In general, bacterial adhesion on sealants was lower compared to adhesion on SS, for surfaces with and without antimicrobials. Antimicrobial coatings on SS surfaces played a role in reducing early-stage biofilm formation for S. capitis, however, no effects were observed for M. lacticum. S. capitis adhesion and biofilm formation were reduced by 8% and 25%, respectively, on SS coated with an antimicrobial substance (SS_4_M), compared to the same surface without the antimicrobial coating (SS_4_control). Incorporation of both antifungicidal and bactericidal agents (S_5_FB) significantly reduced (p ≤ 0.05) early-stage biofilm formation of M. lacticum, compared to the other sealants incoportating either solely antifungal agents (S_2_F) or no active compound (S_control). Furthermore, the thickness of the coating layer correlated weakly with the antimicrobial effect. Hence, equipment manufacturers and food producers should carefully select antimicrobial surfaces as their effects on bacterial adhesion and early-stage biofilm formation depend on the active agent and bacterial species.
... In beef packing plants, the routes of contamination often include multiple media, which could not trace back to a single source, e.g., animals (28). Equipment surface was considered to be a source of recurring contamination of E. coli on meat products, although cattle are significant initial contributors of E. coli (57,58). Thus, it is debatable to continuously use E. coli as an indicator for fecal contamination without considering the environment/process under evaluation, because of its broad range of niches, as reflected in the changes in the population structure as it flows through the beef processing stages. ...
Article
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Antimicrobial interventions have significantly reduced the microbial loads on carcasses/meat products; however, the wide use of chemical and physical biocides has raised concerns over their potential for selecting resistant populations in the beef processing environment. Phenotyping of acid resistance and whole-genome analysis described in this study demonstrated beef processing practices led to differences in acid resistance, genotype, and population structure between carcass- and equipment-associated E. coli but did not select for the acid-resistant population.
... The count of other two isolates was not significantly different (p > 0.05). Even though plastic is hydrophobic in nature, Salmonella biofilms adhere easily to plastic surfaces (Sinde and Carballo, 2000). Results of the present study (Fig. 3a) confirm previous findings as Salmonella produced more biofilms on plastic surfaces, which makes the cell adhesion easier than in other materials concurrent to earlier studies (Joseph et al., 2001;Stepanovic et al., 2003). ...
Article
This study investigates the effect of antibiotics and sanitizers on biofilm forming Salmonella isolated from different seafood contact surfaces. Four Salmonella were isolated from 384 swab samples collected from various contact surfaces of fishing boats, fish landing centres and seafood processing plants. One out of four isolates was from the fishing boat (FB I -1) other three isolates were from the seafood processing plant (FPPII -4, FPPII- 5, FPPI-3). The ability of Salmonella to form biofilms on different contact surfaces (HDPE, stainless steel, wood, glass, tiles) was tested with the microbial load on different incubation days, and a higher count was observed on day five. The effect of sanitizer viz., sodium hypochlorite (20, 50, 100, 200 mg/l) and iodophor (2, 5, 10 mg/l) on the biofilm formed on different seafood contact surfaces were investigated. A reduction of 2 to 3 log was observed on surfaces of HDPE and stainless steel when they were treated with a minimum of 5 mg/l of iodophor or 20 mg/l of sodium hypochlorite after a contact time of 5 min. Antibiotic resistance of biofilm forming Salmonella was tested for different classes of antibiotics (penicillin, ß-lactams, quinolones, macrolides, aminoglycosides, phenol drugs, sulfonamides, cephalosporin). All four isolates showed intermediate resistance to ciprofloxacin, a quinolone drug. Only one isolate FB I -1 (fishing boat deck) expressed resistance to more drugs, viz., ßlactams (AMC, AMP, penicillin G), macrolides (AZM) and nitrofurantoin (NIT). These findings shall help the seafood processors to mitigate the formation of Salmonella biofilms on various seafood contact surfaces with different sanitizers and the antibiotic resistance of biofilm forming Salmonella shall give knowledge on human clinical treatments. With this study, we shall recommend the regulatory authorities control the contamination level of fish handling areas.
... Vibrio can attach to plastic surfaces and create a biofilm, making the use of plastic cutting boards and cooking raw foods extremely prone to cross-contamination [37,69,70]. Additionally, compared to glass and SS surfaces, which are hydrophilic materials, plastic is more likely to allow Salmonella germs to stick to them [37,45,71]. Therefore, it is crucial to avoid contaminating the plastic cutting boards used while preparing or processing food because this leads to vibriosis. ...
Article
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Vibrio parahaemolyticus, one of the most common foodborne pathogenic bacteria that forms biofilms, is a persistent source of concern for the food industry. The food production chain employs a variety of methods to control biofilms, although none are completely successful. This study aims to evaluate the effectiveness of quercetin as a food additive in reducing V. parahaemolyticus biofilm formation on stainless-steel coupons (SS) and hand gloves (HG) as well as testing its antimicrobial activities. With a minimum inhibitory concentration (MIC) of 220 µg/mL, the tested quercetin exhibited the lowest bactericidal action without visible growth. In contrast, during various experiments in this work, the inhibitory efficacy of quercetin at sub-MICs levels (1/2, 1/4, and 1/8 MIC) against V. parahaemolyticus was examined. Control group was not added with quercetin. With increasing quercetin concentration, swarming and swimming motility, biofilm formation, and expression levels of target genes linked to flagellar motility (flaA, flgL), biofilm formation (vp0952, vp0962), virulence (VopQ, vp0450), and quorum-sensing (aphA, luxS) were all dramatically suppressed. Quercetin (0–110 μg/mL) was investigated on SS and HG surfaces, the inhibitory effect were 0.10–2.17 and 0.26–2.31 log CFU/cm2, respectively (p < 0.05). Field emission scanning electron microscopy (FE-SEM) corroborated the findings because quercetin prevented the development of biofilms by severing cell-to-cell contacts and inducing cell lysis, which resulted in the loss of normal cell shape. Additionally, there was a significant difference between the treated and control groups in terms of motility (swimming and swarming). According to our research, quercetin produced from plants should be employed as an antibiofilm agent in the food sector to prevent the growth of V. parahaemolyticus biofilms. These results indicate that throughout the entire food production chain, bacterial targets are of interest for biofilm reduction with alternative natural food agents in the seafood industry.
... Vibrio can attach to surfaces and form a biofilm, making the use of plastic cutting boards and cooking raw foods extremely prone to cross-contamination [33,70,71]. Additionally, compared to glass and SS surfaces, which are hydrophilic materials, plastic is more likely to allow Salmonella germs to stick to them [33,41,72]. Therefore, it is crucial to avoid contaminating the plastic cutting boards used while preparing or processing food because this leads to vibriosis. ...
Article
Full-text available
For the seafood industry, Vibrio parahaemolyticus, one of the most prevalent food-borne pathogenic bacteria that forms biofilms, is a constant cause of concern. There are numerous techniques used throughout the food supply chain to manage biofilms, but none are entirely effective. Through assessing its antioxidant and antibacterial properties, quercetin will be evaluated for its ability to prevent the growth of V. parahaemolyticus biofilm on shrimp and crab shell surfaces. With a minimum inhibitory concentration (MIC) of 220 µg/mL, the tested quercetin exhibited the lowest bactericidal action without visible growth of bacteria. In contrast, during various experiments in this work, the inhibitory efficacy of quercetin without (control) and with sub-MICs levels (1/2, 1/4, and 1/8 MIC) against V. parahaemolyticus was examined. With increasing quercetin concentration, swarming and swimming motility, biofilm formation, and expression levels of related genes linked to flagella motility (flaA and flgL), biofilm formation (vp0952 and vp0962), and quorum-sensing (luxS and aphA) were all dramatically reduced (p < 0.05). Quercetin (0-110 μg/mL) was investigated on shrimp and crab shell surfaces, the inhibitory effects were 0.68-3.70 and 0.74-3.09 log CFU/cm2, respectively (p < 0.05). The findings were verified using field emission scanning electron microscopy (FE-SEM), which revealed quercetin prevented the development of biofilms by severing cell-to-cell contacts and induced cell lysis, which resulted in the loss of normal cell shape. Furthermore, there was a substantial difference in motility between the treatment and control groups (swimming and swarming). According to our findings, plant-derived quercetin should be used as an antimicrobial agent in the food industry to inhibit the establishment of V. parahaemolyticus biofilms. These findings suggest that bacterial targets are of interest for biofilm reduction with alternative natural food agents in the seafood sector along the entire food production chain.
... after sanitation (tray in freezer with fish/gray lug, fish holding tray for graded fillet, tote with whole fish, belt before injection, ice container/ice pipe, and waste belt) that are made of some type of plastic material (Tables 3 and 4). Although an attachment strength study for Listeria spp. was not performed during this study, different authors have reported that Listeria cells can attach better to rubber and plastic than to glass and stainless steel [49,50]. For that reason, it is important to have an effective removal of organic waste and cleaning prior to the application of sanitizers on those sites. ...
Article
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The catfish industry is important to the United States economy. The present study determined the levels of microbial indicators and the prevalence of Listeria spp. and Listeria monocytogenes at catfish farms and catfish processing plants. Live fish, water, and sediment samples were analyzed in farms. Fish skin, fillets, chiller water, and environmental surfaces were assessed at the processing plants both during operation and after sanitation. Live fish had 2% prevalence of Listeria monocytogenes, while sediment and water were negative for Listeria. Live fish skin counts averaged 4.2, 1.9, and 1.3 log CFU/cm2 aerobic (APC), total coliform (TCC) and generic Escherichia coli counts, respectively. Water and sediment samples averaged 4.8 and 5.8 log CFU/g APC, 1.9 and 2.3 log CFU/g TCC, and 1.0 and 1.6 log CFU/g generic E. coli counts, respectively. During operation, Listeria prevalence was higher in fillets before (57%) and after (97%) chilling than on fish skin (10%). Process chiller water had higher (p ≤ 0.05) APC, TCC, and Listeria prevalence than clean chiller water. After sanitation, most sampling points in which Listeria spp. were present had high levels of APC (>2.4 log CFU/100 cm2). APC combined with Listeria spp. could be a good approach to understand microbial contamination in catfish plants.
... Foodborne pathogens can attach to plastic surfaces and form a biofilm, making the use of plastic cutting boards and cooking raw foods extremely prone to cross-contamination [22,62,63]. Additionally, compared to glass and SS surfaces, which are hydrophilic materials, plastic is more likely to allow Salmonella germs to stick to them [22,35,64]. Therefore, it is crucial to avoid contaminating the plastic cutting boards used while preparing or processing food because this leads to listeriosis. ...
Article
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Listeria monocytogenes is the species of foodborne pathogenic bacteria that causes the infection listeriosis. The food production chain employs various methods to control biofilms, although none are completely successful. This study evaluates the effectiveness of quercetin as a food additive in reducing L. monocytogenes mixed cultures (ATCC19113, ATCC19117, and ATCC15313) biofilm formation on stainless steel (SS), silicon rubber (SR), and hand glove (HG) coupons, as well as tests its antimicrobial activities. With a minimum inhibitory concentration (MIC) of 250 µg/mL, the tested quercetin exhibited the lowest bactericidal action with no visible bacterial growth. In contrast, during various experiments in this work, the inhibitory efficacy of quercetin at sub-MICs levels (1/2, 1/4, and 1/8 MIC) against L. monocytogenes was examined. A control group was not added with quercetin. The current study also investigates the effect of quercetin on the expression of different genes engaged in motility (flaA, fbp), QS (agrA), and virulence (hlyA, prfA). Through increasing quercetin concentration, swarming and swimming motility, biofilm formation, and expression levels of target genes linked to flagella motility, virulence, and quorum-sensing were all dramatically reduced. Quercetin (0–125 μg/mL) was investigated on the SS, SR, and HG surfaces; the inhibitory effects were 0.39–2.07, 0.09–1.96 and 0.03–1.69 log CFU/cm2, respectively (p < 0.05). Field-emission scanning electron microscopy (FE-SEM) corroborated the findings because quercetin prevented the development of biofilms by severing cell-to-cell contacts and inducing cell lysis, which resulted in the loss of normal cell shape. Our findings suggest that plant-derived quercetin should be used as an antimicrobial agent in the food industry to control the development of L. monocytogenes biofilms. These outcomes suggest that bacterial targets are of interest for biofilm reduction, with alternative natural food agents in the food sector along the entire food production chain.
... The modification of food contact surfaces seemed to be the first mode of action against the attachment of bacterial cells. The complexity of particular parts of processing equipment (joints) or bacterial cells "hidden" in cracks and scratches appearing on the surface do not guarantee complete sanitization [103]. Therefore, it is a valuable strategy to have the initial bacterial attachment on the surface of materials under control. ...
Article
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This review deals with microbial adhesion to metal-based surfaces and the subsequent biofilm formation, showing that both processes are a serious problem in the food industry, where pathogenic microorganisms released from the biofilm structure may pollute food and related material during their production. Biofilm exhibits an increased resistance toward sanitizers and disinfectants, which complicates the removal or inactivation of microorganisms in these products. In the existing traditional techniques and modern approaches for clean-in-place, electrochemical biofilm control offers promising technology, where surface properties or the reactions taking place on the surface are controlled to delay or prevent cell attachment or to remove microbial cells from the surface. In this overview, biofilm characterization, the classification of bacteria-forming biofilms, the influence of environmental conditions for bacterial attachment to material surfaces, and the evaluation of the role of biofilm morphology are described in detail. Health aspects, biofilm control methods in the food industry, and conventional approaches to biofilm removal are included as well, in order to consider the possibilities and limitations of various electrochemical approaches to biofilm control with respect to potential applications in the food industry.
... In beef packing plants, the routes of contamination often include multiple media, which could not trace back to a single source, e.g., animals (28). Equipment surface was considered to be a source of recurring contamination of E. coli on meat products, although cattle are significant initial contributors of E. coli (57,58). Thus, it is debatable to continuously use E. coli as an indicator for fecal contamination without considering the environment/process under evaluation, because of its broad range of niches, as reflected in the changes in the population structure as it flows through the beef processing stages. ...
... High adhesion on Teflon has previously been reported for Pseudomonas aeruginosa (Alfa et al. 2017), Salmonella spp. and Listeria monocytogenes (Sinde and Carballo 2000). Although glass is very hydrophilic, with contact angles from 12.3 ± 2 to 25.3 ± 6.5 , it was the second most attractive material for C. metallidurans CH34 biofilm formation. ...
Article
Bacteria biofilm formation and its complications are of special concern in isolated structures, such as offshore stations, manned submarines and space habitats, as maintenance and technical support are poorly accessible due to costs and/or logistical challenges. In addition, considering that future exploration missions are planned to adventure farther and longer in space, unlocking biofilm formation mechanisms and developing new antifouling solutions are key goals in order to ensure spacecraft's efficiency, crew's safety and mission success. In this work, we explored the interactions between Cupriavidus metallidurans, a prevalently identified contaminant onboard the International Space Station, and aerospace grade materials such as the titanium alloy TiAl6V4, the stainless steel AISI 316 (SS316) and Polytetrafluoroethylene (PTFE) or Teflon. Borosilicate glass was used as a control and all surfaces were investigated at two different pH values (5.0 and 7.0). Biofilms were almost absent on stainless steel and the titanium alloy contrary to Teflon and glass that were covered by an extensive biofilm formed via monolayers of scattered matrix-free cells and complex multilayered clusters or communities. Filamentous extracellular DNA structures were observed specifically in the complex multilayered clusters adherent to Teflon, indicating that the employed attachment machinery might depend on the physicochemical characteristics of the surface.
... detection. Studies (Blackman and Frank, 1996;Mafu et al., 1990;Sinde and Carballo, 2000) have demonstrated Listeria spp. can attach to a variety of surfaces, including stainless steel, concrete, rubber, and plastics. ...
Article
Listeria species prevalence has been investigated at nearly all stages of the fresh produce supply chain; however, it has not been examined in transportation and distribution center (DC) related environments. Between December 2019 and March 2021, 18 DCs handling fresh produce were environmentally sampled for Listeria. Swab samples were collected from a variety of surfaces (e.g., floors, pallets, forklifts) in several areas of each DC (e.g., cold storage, shipping and receiving docks). Impaction air samples, relative humidity, and temperature data were also collected. While no Listeria spp. were isolated from air samples (n = 170), they were isolated from 49 of 982 (ca. 5%) environmental samples. The proportion of Listeria spp. positive samples varied significantly across individual DCs (P < 0.01). Several facility characteristics were significantly associated with a Listeria spp. positive sample, such as zone, sampling site dryness, and cleaning regimen. A random forest model (sensitivity: 0.786, specificity: 0.874) identified geographical location and general sampling location (e.g., cold storage rooms, shipping docks) as the two most important variables associated with Listeria spp. detection. This study identified likely harborage sites (e.g., floors, cleaning equipment) of Listeria spp. in DCs across the US and emphasized the importance of sanitation operations in Listeria-prone areas.
... Several studies have evaluated the effectiveness of different sanitizers against L. monocytogenes on different FCS material types such as polyethylene, stainless steel, polyester, rubber, and polytetrafluorethylene (Teflon®) (Chaturongkasumrit et al., 2011;Hua et al., 2019;Krysinski et al., 1992;Park and Kang, 2017;Sinde and Carballo, 2000). However, research that evaluates cleaning and sanitizing methods on actual surfaces currently used in a produce industry is lacking. ...
Article
Previous foodborne listeriosis outbreaks and recalls of fresh produce have been linked to cross-contamination with food contact surfaces (FCS) of packing equipment. Thus, effective cleaning and sanitation practices should be implemented in the short-term to contribute to the overall food safety objective for FCS which have a suboptimal hygienic design. This research aimed to evaluate the efficacy of seven cleaning and sanitation treatment combinations against Listeria innocua populations on FCS common to produce packinghouses that have been found to have a higher prevalence of Listeria spp. harborage. Polishing brushes made of two different materials (100% nylon and nylon/horsehair mix), 100% polyethylene wash brushes, stainless steel rollers and polytetrafluoroethylene (Teflon®) wrapped rollers, and interlocking conveyor belts were evaluated (n = 6 per treatment). These FCS were inoculated with L. innocua (9 log CFU/mL) and fouled with food-grade wax, with the exception of brush rollers that are encountered before waxing. Treatments included the use chlorine (200 ppm), peroxyacetic acid (PAA) (500 ppm) for 15 min, alone or in combination with an alkaline detergent (1.6%) or a degreaser, and the use of steam at 95 °C for 15 s. L. innocua was enumerated and the log reduction was calculated and compared to untreated controls. Horsehair mix polishing brushes were the surface with the lowest log reduction regardless of treatment applied (p < 0.05). Compared to 100% nylon polishing brushes, where a >3 log reduction was reached, horsehair mix brushes only reached this level of reduction when degreaser + PAA was applied. For both types of rollers and interlocking conveyor belt, an effective wax removal using a degreaser or detergent followed by sanitizer application caused the greatest L. innocua reduction (>5 log reduction). The application of steam did not show a significant log reduction on any surface (p > 0.05). This study highlights that cleaning and sanitation strategies must focus on effective wax removal if applied postharvest. In addition, 100% nylon polishing brushes could potentially offer a better hygienic design in produce packinghouses compared to the horsehair mix.
... Plusieurs paramètres peuvent affecter l'attachement des cellules sur le support y compris l'hydrophobicité de ce dernier et sa tension de surface. Les bactéries tendent à s'attacher plus facilement sur les surfaces hydrophobes [376]. L'utilisation d'un support avec une surface hydrophile limite l'accrochage et la formation de biofilm [377]. ...
Thesis
La compréhension de l’interaction entre les microorganismes est primordiale pour le développement de nouveaux produits de biocontrôle. Le champignon Trichoderma harzianum et la bactérie Bacillus velezensis sont exploités pour leur potentiel dans la lutte contre les phytopathogènes. Deux stratégies de coculture de ces deux microorganismes sont mises au point afin de déterminer les conditions menant à une interaction qui augmente l’activité de biocontrôle de ce couple, définie en termes de production de lipopeptides par la bactérie. Le milieu de culture varie essentiellement entre ces deux stratégies. Les deux milieux varient en fonction de la disponibilité de nutriments pour les microorganismes. Dans un milieu riche, où Bacillus et Trichoderma disposent de tous les éléments nécessaires à leur croissance, la bactérie se développe au dépriment du champignon grâce à son rythme de croissance plus rapide et à la production des lipopeptides antifongiques. L’inoculation séquentielle de Trichoderma suivi par Bacillus permet de résoudre ces problèmes empêchant la coexistence des deux microorganismes. Toutefois, dans toutes ces approches, la présence de Trichoderma n’a pas influencé la production de lipopeptides par B. velezensis GA1 et conséquemment son activité en biocontrôle. L’effet sur la production de ces NRPs est plus remarqué dans un milieu minimum conçu pour imposer une dépendance nutritionnelle entre Bacillus et Trichoderma. Le requis de la bactérie d’une source d’azote produite par T. harzianum, principalement sous forme de peptides et d’acides aminés, leur permet de coexister en coculture. La présence physique du champignon inhibe la production de lipopeptides mais la présence de son surnageant la promeut. Le dialogue moléculaire entre le couple Trichoderma – Bacillus requiert d’être décrypté davantage afin de l’exploiter dans des applications agricoles.
... Several studies have evaluated the effectiveness of different sanitizers against L. monocytogenes on different FCS material types such as polyethylene, stainless steel, polyester, rubber, and polytetrafluorethylene (Teflon®) (Chaturongkasumrit et al., 2011;Hua et al., 2019;Krysinski et al., 1992;Park and Kang, 2017;Sinde and Carballo, 2000). However, research that evaluates cleaning and sanitizing methods on actual surfaces currently used in a produce industry is lacking. ...
... The use of plastic cutting boards for processing and cooking raw foods is very susceptible to cross-contamination [50] because Salmonella can adhere to the surfaces of plastic to form a biofilm [11]. Additionally, because plastic is a hydrophobic material, Salmonella bacteria are more likely to adhere on it than on glass and stainless steel surfaces, which are hydrophilic materials [51]. Therefore, it is essential to prevent contamination of plastic cutting boards used when processing or cooking foods, which cause Salmonellosis. ...
Article
Full-text available
Quercetin is an active nutraceutical element that is found in a variety of foods, vegetables, fruits, and other products. Due to its antioxidant properties, quercetin is a flexible functional food that has broad protective effects against a wide range of infectious and degenerative disorders. As a result, research is required on food-contact surfaces (rubber (R) and hand gloves (HG)) that can lead to cross-contamination. In this investigation, the inhibitory effects of quercetin, an antioxidant and antibacterial molecule, were investigated at sub-MIC (125; 1/2, 62.5; 1/4, and 31.25; 1/8 MIC, μg/mL) against Salmonella Typhimurium on surfaces. When quercetin (0–125 μg/mL) was observed on R and HG surfaces, the inhibitory effects were 0.09–2.49 and 0.20–2.43 log CFU/cm2, respectively (p < 0.05). The results were confirmed by field emission scanning electron microscopy (FE-SEM), because quercetin inhibited the biofilms by disturbing cell-to-cell connections and inducing cell lysis, resulting in the loss of normal cell morphology, and the motility (swimming and swarming) was significantly different at 1/4 and 1/2 MIC compared to the control. Quercetin significantly (p < 0.05) suppressed the expression levels of virulence and stress response (rpoS, avrA, and hilA) and quorum-sensing (luxS) genes. Our findings imply that plant-derived quercetin could be used as an antibiofilm agent in the food industry to prevent S. Typhimurium biofilm formation.
... The use of PLA cutting boards for processing and cooking raw foods is very susceptible to cross-contamination (Stepanović et al., 2004) because Salmonella can adhere to the surfaces of PLA to form a biofilm . In addition, Salmonella is known to adhere more easily to hydrophobic materials, such as PLA and wood, than hydrophilic materials, such as glass and stainless steel (Sinde & Carballo, 2000). Therefore, it is essential to prevent contamination of PLA cutting boards used when processing or cooking foods because even low numbers of cells can cause salmonellosis. ...
Article
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... detection. Studies (Blackman and Frank, 1996;Mafu et al., 1990;Sinde and Carballo, 2000) have demonstrated Listeria spp. can attach to a variety of surfaces, including stainless steel, concrete, rubber, and plastics. ...
Chapter
In nature, microorganisms are often found as highly organized, heterogeneous structures called biofilms, the characteristics of which are fundamentally different from microbes in planktonic suspensions. Host colonization by pathogens and several persistent infections caused by them are also linked to the ability of these microorganisms to shift from planktonic (free-floating) to sessile (biofilm) state. Dental disorders, such as caries, periodontal and endodontic diseases, are major public health issues worldwide and are known to be due to polymicrobial biofilms. Despite advances in understanding the mechanisms of biofilm formation and persistence, novel and effective treatment options for prevention and eradication of biofilms remain scarce. During the last decade, techniques like Next Generation Sequencing have enabled us to understand the microbiome in the oral biofilms and have therefore led to explorations of innovative approaches for their management; use of nanomaterials being one such approach. Nanotechnology offers new possibilities for preventive/curative therapies for biofilm-associated oral diseases. This chapter provides an insight into the use of nanoparticle-based systems as active therapeutic agents to target specific microbial and biofilm features. Nanoparticles as vehicles to transport drugs to the infected site are also discussed.
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Listeria monocytogenes (in the meat, fish and seafood, dairy and fruit and vegetable sectors), Salmonella enterica (in the feed, meat, egg and low moisture food sectors) and Cronobacter sakazakii (in the low moisture food sector) were identified as the bacterial food safety hazards most relevant to public health that are associated with persistence in the food and feed processing environment (FFPE). There is a wide range of subtypes of these hazards involved in persistence in the FFPE. While some specific subtypes are more commonly reported as persistent, it is currently not possible to identify universal markers (i.e. genetic determinants) for this trait. Common risk factors for persistence in the FFPE are inadequate zoning and hygiene barriers; lack of hygienic design of equipment and machines; and inadequate cleaning and disinfection. A well‐designed environmental sampling and testing programme is the most effective strategy to identify contamination sources and detect potentially persistent hazards. The establishment of hygienic barriers and measures within the food safety management system, during implementation of hazard analysis and critical control points, is key to prevent and/or control bacterial persistence in the FFPE. Once persistence is suspected in a plant, a ‘seek‐and‐destroy’ approach is frequently recommended, including intensified monitoring, the introduction of control measures and the continuation of the intensified monitoring. Successful actions triggered by persistence of L. monocytogenes are described, as well as interventions with direct bactericidal activity. These interventions could be efficient if properly validated, correctly applied and verified under industrial conditions. Perspectives are provided for performing a risk assessment for relevant combinations of hazard and food sector to assess the relative public health risk that can be associated with persistence, based on bottom‐up and top‐down approaches. Knowledge gaps related to bacterial food safety hazards associated with persistence in the FFPE and priorities for future research are provided.
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A novel procedure for the quantitative analysis of biofilm formation by bacteria and yeasts, the Plate-hanging method, was developed. In this system, various polymer disks were hung from the lid of a 6-well plate, immersed in a cell suspension, and moderately shaken (70 rpm). In order to verify the validity of the procedure, the effects of the solid surface hydrophobicity of the test disks and the cell surface hydrophobicities of microorganisms on biofilm formation were investigated. Biofilm formation of bacteria and yeasts on the solid surface strongly depended on hydrophobic interactions between the solid surface and the cell surface. A positive correlation between the hydrophobic properties of substratum and cell surfaces was observed. On the other hand, hydrophilic yeasts preferentially adsorbed onto relatively hydrophilic surfaces. Moreover, the plate-hanging method coupled with the periodic exchange of the liquid medium enabled the quantification of long-term biofilm growth.
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The carriers of nosocomial infections are the hands of medical personnel and inanimate surfaces. Both hands and surfaces may be contaminated as a result of contact with the patient, their body fluids, and touching contaminated surfaces in the patient’s surroundings. Visually clean inanimate surfaces are an important source of pathogens. Microorganisms have properties thanks to which they can survive in unfavorable conditions, from a few days to several months. Bacteria, viruses and fungi are able to transmit from inanimate surfaces to the skin of the patient and the medical staff. These pathogens include SARS-CoV-2, which can survive on various types of inanimate surfaces, being a potential source of infection. By following the recommendations related to washing and disinfecting hands and surfaces, and using appropriate washing and disinfecting agents with a broad biocidal spectrum, high material compatibility and the shortest duration of action, we contribute to breaking the chain of nosocomial infections.
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Chapter
Microbes are thought to be the first life on the earth. Over the years, microbes have changed considerably to mutate themselves to support human life and a few other strains to change to an extent to pose danger to the human life. Over the years they have also learnt to adopt to various environments. The effectiveness of the microbial strain is highly influenced by the microbe–surface interactions. This chapter deals with various types of microbe–surface interactions and how the environment affects the interactions. The chapter also explores the concepts of engineering the microbe–surface interactions to exploit in various applications, like biosensors, antifouling surfaces, controlling infections on plants and animals, etc.
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A variety of chemical cleaning and sanitizing compounds were evaluated for their ability to remove and/or inactivate surface adherent Listeria monocytogenes. Adherent cells were obtained by incubating 1-cm2 chips of stainless steel or plastic conveyor belts with a multistrain cocktail of L. monocytogenes for 24 h at 25°C. Resistance of adherent cells to sanitizers was dependent upon the surface studied, being greatest on polyester/ polyurethane followed by polyester and stainless steel. Biofilm removal with cleaners followed the same pattern as sanitizers with the polyester/polyurethane surface being most difficult to clean. Complete biofilm removal and/or inactivation was obtained in many cases where the surface was first cleaned prior to exposure to sanitizer. The data support conventional wisdom in that cleaning must precede sanitizing in order to remove and inactivate microorganisms. Listeria biofilms should be controllable by combining Good Manufacturing Practices with the discipline of a Hazard Analysis Critical Control Point Program. Copyright ©, International Association of Milk, Food and Environmental Sanitarians.
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Surface-adherent microcolonies of Listeria monocytogenes were obtained by growing cells on glass slides immersed in a low nutrient medium containing excess glucose. The susceptibility of the adherent populations to benzalkonium chloride (100, 400, and 800 ppm solutions), anionic acid sanitizer (200 and 400 ppm solutions), and heat (55 and 70°C) was determined. Adherent microcolony cells decreased by 2 to 3 log cycles immediately after exposure to the sanitizers. The remaining population of microcolony cells survived 20 min of exposure demonstrating resistance to both sanitizers at all concentrations. Adherent single cells exhibited an initial 3 to 5 log decline in numbers and reached undetectable levels after 12 to 16 min of exposure to the sanitizers. Planktonic cells were reduced to undetectable levels after 30 sec exposure to the lowest concentration of each sanitizer. Removing adherent cells from the surface increased their sanitizer susceptibility to near that of planktonic cells. Heating adherent microcolonies at 70°C for 5 min resulted in a less than 5-log decrease in population with a surviving population of over 10 cfu/sq cm. These results demonstrate the ability of L. monocytogenes to develop resistance to inactivating agents when exposed to specific growth environments.
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Effective food plant cleaning procedures remove microbial nutrients from surfaces, which could result in contaminating bacteria being subject to a starvation microenvironment. This research investigated the effect of starvation on the susceptibility of Listeria monocytogenes to benzalkonium chloride (BAC). Cells were starved in phosphate buffer at 21°C for 4 d. Biofilm and planktonic listeriae reacted differently to starvation. When cells were grown in tryptic soy broth (TSB), starvation reduced the susceptibility of planktonic cells to BAC by 2.3- to 4.7-fold but had no effect on the susceptibility of biofilm cells. Planktonic cells grown in diluted TSB were 390 times more resistant than normal TSB-grown cells, but when these cells were starved, they lost their increased resistance. This phenomenon was not observed with biofilm cells. Increased resistance of listeriae grown in diluted TSB was associated with dilution of the salt/buffer components of the medium. Sanitizer-treated cells were enumerated by using tryptic soy agar-yeast extract pour plates and by a direct viable count method. Results indicate that some cells exposed to BAC were not detected by the plate count procedure but were still viable.
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The effects of milk and individual milk components on the attachment of Listeria monocytogenes and Salmonella typhimurium to two commonly used materials in the dairy industry were studied. Attachment of both organisms to stainless steel and Buna-N was significantly inhibited by the presence of skim, 2%, whole, or chocolate 2% milk compared to the phosphate-buffered saline (PBS) control. The addition of individual milk components, casein, α-lactalbumin, and β-lactoglobulin to the attachment menstruum significantly reduced attachment. Pretreating surfaces with milk and milk components for 1 h prior to attachment in PBS gave similar results. The presence of lactose did not affect attachment of either organism; however, attachment of S. typhimurium was significantly decreased on pretreated Buna-N. Cells of either organism pretreated with skim milk or β-lactoglobulin prior to attachment in PBS showed significantly less attachment than untreated cells. Pretreating S. typhimurium cells with casein had no effect on attachment to stainless steel. Pretreatment of S. typhimurium with lactose increased attachment to both surfaces while pretreatment had no effect on L. monocytogenes . Attachment of both organisms was significantly reduced in diluted whole milk. Both organisms attached significantly less to surfaces soiled with one or more layers of whole milk.
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We discuss various important aspects of the theory of multiphoton free–free transitions. First we show, in the simple framework of potential scattering, the necessity for a description of the laser field to take into account the actual experimental conditions such as beam focusing and pulsed and multimode operations. We then generalize the study to the collisions of fast electrons with atoms in intense laser fields and show how the dressing of the atomic states by the external radiation field can affect the scattering cross sections. Finally, we consider the role played by statistical fluctuations of the laser field. To this end, we develop the pre-Gaussian model of laser noise and show how this formalism can be included in the theory of multiphoton free–free transitions.
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This study investigated the physicochemical forces involving the adhesion of Listeria monocytogenes to surfaces. A total of 22 strains of L. monocytogenes were compared for relative surface hydrophobicity with the salt aggregation test. Cell surface charges and hydrophobicity of L. monocytogenes Scott A were also determined by electrophoretic mobility, hydrophobic-interaction chromatography, and contact angle measurements. Electrokinetic measurements indicated that the strain Scott A has a negative electrophoretic mobility. Physicochemical characterization of L. monocytogenes by various methods indicates that this microorganism is hydrophilic. All L. monocytogenes strains tested with the salt aggregation test method aggregated a at very high ammonium sulfate molarities. The hydrophobicity-interaction chromatography results show that L. monocytogenes Scott A cells do not adhere to octyl-Sepharose unless the pH is low. Results from contact angle measurements showed that the surface free energy of strain Scott A was 65.9 mJ.m-2, classifying this microorganism as a hydrophilic bacterium. In addition, the interfacial free energy of adhesion of L. monocytogenes Scott A estimated for polypropylene and rubber was lower than that for glass and stainless steel. However, these theoretical implications could not be correlated with the attachment capabilities of L. monocytogenes.
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The adhesion of the oral bacterium Streptococcus sanguis CH3 to various polymeric surfaces with surface free energies (gamma s) ranging from 22 to 141 erg cm-2 was investigated. Suspensions containing nine different bacterial concentrations (2.5 X 10(7) to 2.5 X 10(9) cells per ml) were used. After adhesion for 1 h at 21 degrees C and a standardized rinsing procedure, the number of attached bacteria per square centimeter (nb) was determined by scanning electron microscopy. The highest number of bacteria was consistently found on polytetrafluorethylene (gamma s = 22 erg cm-2), and the lowest number was found on glass (gamma s = 141 erg cm-2) at all bacterial concentrations tested. The overall negative correlation between nb and gamma s was weak. However, the slope of the line showing this decrease, calculated from an assumed linear relationship between nb and gamma s, appeared to depend strongly on the bacterial concentration and increased with increasing numbers of bacteria in the suspension. Analysis of the data for each separate polymer showed that the numbers of attached cells on polyvinyl chloride and polypropylene were higher but that those on polycarbonate were lower than would be expected on basis of a linear relationship between nb and gamma s. Desorption experiments were performed by first allowing the bacteria to attach to substrata for 1 h, after which the substrata and attached bacteria were removed to bacterial suspensions containing 10-fold lower bacterial concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
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An experimental technique is described to determine contact angles on bacterial layers deposited on cellulose triacetate filters. Measurements with water, water-n-propanol mixtures, and alpha-bromonaphthalene were employed to calculate surface free energies of various oral bacteria. Differences of 30 to 40 erg cm-2 were obtained for four different bacterial species isolated from the human oral cavity, if the concept of dispersion and polar surface free energies is applied. The free energies obtained were used to calculate interfacial free energies of adhesion of these bacteria from saliva onto tooth surfaces. Bacterial adhesion is energetically unfavorable, if the enamel surface free energy is less than 50 erg cm-2.
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Established (48- and 72-h) Salmonella enteritidis biofilms grown in glass flow cells with or without artificial crevices (0.5-, 0.3-, and 0.15-mm widths) were subjected to a 10% trisodium phosphate (TSP) solution under different flow regimens (0.3, 0.6, 1.2, and 1.8 cm s-1). The abundance of biofilm remaining after TSP treatment, the biocidal efficacy of TSP, and the factors which contributed to bacterial survival were then evaluated by using confocal laser microscopy and a fluorescent viability probe. Biofilm age affected the amount of biofilm which remained following a 15-s exposure to TSP. After TSP treatment of 48-h biofilms, 29% of the original biofilm remained at the biofilm-liquid interface, whereas 75% of the biofilm remained at the base (the attachment surface). Following TSP treatment of 72-h biofilms, 27% of the biofilm material remained at the biofilm-liquid interface, 73% remained at the 5-micron depth, and 91% remained at the biofilm base. Results obtained using the BacLight viability probe indicated that TSP exposure killed all the cells in 48-h biofilms, whereas in the thicker 72-h biofilms, surviving bacteria (approximately 2% of the total) were found near the 5- and 0-micron depths. In the presence of artificially constructed crevices, an inverse relationship was shown to exist between bacterial survival (ranging from approximately 13 to 83% of total biofilm material) and crevice width. This relationship was further influenced by the velocity of TSP flow; high TSP flow velocities (1.8 cm s-1) resulted in the lowest number of surviving bacteria at the base of crevices (approximately 42% survival). Extended time courses demonstrated that after TSP stress was relieved, biofilms continued to grow within crevices but not in systems without crevices. It is suggested that advective TSP flux into crevices and through the biofilm matrix was enhanced under conditions of high flow. These results suggest that the inherent roughness of the substratum on which the biofilm was grown and the timing of TSP application are important factors controlling the efficacy of TSP treatment.
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Changes over time of microbial load, surface free energy, and roughness of a variety of floor materials were investigated after hygiene operations in meat, pastry, and milk processing environments. Measurements were made in the laboratory on test plates which had been inserted in floors of food premises and subjected to the habitual fouling-cleaning cycles for up to 16 weeks. Microbial contamination of floor materials, assessed after sonication, appeared to be controlled in the milk site, which was generally dry. In both pastry and meat sites a specific microbial population developed and could stabilize to levels up to 10(4) and 10(6) CFU cm(-2), respectively. In the meat site bacterial contamination could be as high as 10(7) CFU cm(-2) on one rough floor material. After introduction in the premises, all flooring materials tended to have similar surface free energy values that could be simulated in the laboratory either perfectly by conditioning the surface with the treated food (in the case of the milk premises) or approximately by conditioning the surface with the hygiene agents used (in the case of the meat and pastry premises).
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This study examined the hypothesis that solid surfaces may stimulate attached bacteria to produce exopolymers. Addition of sand to shake-flask cultures seemed to induce exopolymer synthesis by a number of subsurface isolates, as revealed by optical microscopy. Several additional lines of evidence indicated that exopolymer production by attached cells (in continuous-flow sand-packed columns) was greater than by their free-living counterparts. Total carbohydrates and extracellular polysaccharides, both normalized to cell protein, were greater (2.5- and 5-fold, respectively) for attached cells than for free-living cells. Also, adsorption of a polyanion-binding dye to the exopolymer fraction was sixfold greater for attached cells than for unattached cells. When surface-grown cells were resuspended in fresh medium, exopolymer production decreased to the level characteristic of unattached cells, which ruled out the possibility that attached cells comprised a subpopulation of sticky mucoid variants. The mechanism by which attachment stimulated exopolymer synthesis did not involve changes of the specific growth rate, growth stage, or limiting nutrient.
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Physico-chemical surface parameters, wettability and net surface charge, were measured for Pseudomonas cells and a range of surface materials used in the food industry. Data were obtained for surfaces and organisms before and after treatment with a solution of pork extract produced from fresh meat. Stainless steel (AISI 304) was hydrophilic and remained so after treatment, all the plastics surfaces were converted from hydrophobic to hydrophilic. Net surface charge on the stainless steel was markedly decreased by the meat juice but the plastics showed only minor changes. Examination of detachment of precolonised surfaces using a Fowler radial flow shear apparatus showed that all three surface materials performed in different ways of both when untreated and treated. Possible reasons and the practical applications are briefly considered.
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This paper presents a hypothesis on the importance of initial microbial adhesion in the overall process of biofilm formation. The hypothesis is based on the realization that dynamic shear conditions exist in many environments, such as in the oral cavity, or on rocks and ship hulls. Recognizing that an entire biofilm is detached during high shear once the bond between the initially adhering organisms and a surface (often constituted through a so-called ‘conditioning film’) is broken, it becomes clear that research should focus on detachment rather than adhesion. Experiments were done in a parallel plate flow chamber in which attempts were made to detach adhering oral streptococci from glass by applying a high shear caused by the passage of a bubble, giving an air-liquid interface. Detachment of streptococci from bare glass and from an initially adhering actinomycete strain appeared not to occur. However, substantial detachment of adhering streptococci occurred when adhesion was mediated through a salivary conditioning film, presumably because of cohesive failure in the conditioning film.
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The process of bacterial attachment to solid surfaces comprises three components, i.e., the bacterial surface, the substratum, and the liquid medium, all of which have been shown to affect the thermodynamics of adhesion. Different bacterial strains and phenotypes can differ considerably with respect to cell surface composition, and thus surface free energy. Accordingly, attachment ability ranges from bacteria which attach readily to surfaces to those which have little adhesive ability. Influence of substratum properties was shown by the relationship between numbers of attached bacteria and substratum work of adhesion for water (WA). Maximum attachment occurred within a substratum WA range of 75 to 105 mJ m−2, but the WA at peak attachment was not the same for all bacteria tested. The liquid medium influences attachment because of the (i) interaction between water and the substratum and bacterial surfaces and the presence of (ii) dissolved macromolecules, which tend to adsorb on surfaces, and (iii) surface active agents which influence surface tension and thus the thermodynamics of adhesion. Dimethyl sulfoxide and a series of low-molecular-weight alcohols were shown to affect numbers of attached cells by affecting liquid surface tension.
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An equation of state is developed which allows the surface tension of a low-energy solid to be determined from a single contact angle formed by a liquid which is chemically inert with respect to the solid and whose liquid surface tension is known. The equation of state is obtained using two independent methods. In the first one, similar arguments to those in previous papers are used; however, the qualitative argument, based on the general appearance of plots, is replaced by computer curve fitting and statistical analysis. The second method, which has not been employed heretofore, treats the solid surface tension as an adjustable parameter. Molecular arguments in conjunction with the interaction parameter Φ are used to eliminate poor choices of the solid surface tension. The results are in excellent agreement with the first method.The range of validity of the equation of state and practical points in its application are discussed.
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Microbial adhesion to hydrocarbons (MATH) is the most commonly used method to determine microbial cell surface hydrophobicity. Since, however, the assay is based on adhesion, it is questionable whether the results reflect only the cell surface hydrophobicity or an interplay of hydrophobicity and surface charge properties. In order to demonstrate the involvement of electrostatic interactions in MATH hydrophobicities by MATH (kinetic mode) were measured in 10 mM potassium phosphate solutions at different pH's and compared with the zeta potentials of the microorganisms and of hexadecane droplets in the same solution. Two oral, microbial strains were involved: Streptococcus salivarius HB (a hydrophobic strain by MATH) and Streptococcus salivarius HB-C12 (a hydrophilic strain by MATH). The initial removal rates of S. salivarius HB-C12 by hexadecane were zero over the entire pH range (pH 2-pH 9) and its zeta potentials were negative in this pH range. S. salivarius HB, however, had an isoelectric point (IEP) at pH 3.2 and accordingly a positive zeta potential below IEP. Correspondingly, the initial removal rates found for this strain were high (2.6 min−1) below and around IEP and much lower (∽ 0.5 min−1) above IEP. Surprisingly, the hexadane droplets also had highly negative zeta potentials above pH 4 and appeared uncharged in the pH range 2–3. Taking the product of the bacterial δb and hexadecane δh zeta potentials as a measure for electrostatic interactions, it was observed that the measured hydrophobicity of S. salivarius HB, but nut of the hydrophilic strain S. salivarius HB-C12, depended on electrostatic interactions as well. The highest removal rates by hexadecane were found in the absence of electrostatic interactions, i.e. in the pH range close to the IEP's of the interacting particles. It is concluded that, in general, MATH does not measure cell surface hydrophobicity but an interplay of hydrophobicity and electrostatic interactions. The involvement of electrostatoc interactions in MATH can be reduced by performing the test under ionic conditions in which either the cells or the hydrocarbon droplets (or both) are uncharged.
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From the contact angle determined with one liquid (of known surface tension) only, it is possible to obtain the values of the surface tensions γSV and γSL, via the equation of state (1): where the subscripts S and L stand for the solid S and the liquid L, whilst the subscript V stands for vapor. In conjunction with Young's equation (2): relation [l] yields: With the help of a computer program values for γsv (1) and for γSl (3) can be derived for different values of the contact angle 8 obtained with a liquid of given γLV
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Microbial contamination of food-contact surfaces is an ongoing concern for the food industry. Under favorable conditions, bacterial cells can adhere and reproduce. Such microorganisms, if not completely removed, can contribute to the formation of biofilms that will compromise the quality and safety of foods. By understanding the relationship between surface conditions and microbial adhesion, strategies can be developed that when realized would greatly inhibit, if not prevent, the attachment of bacteria and spores.
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Microbial colonization of surfaces (biofilms) have been documented in many environments. Recently, researchers have suggested that biofilms may be a source of contamination in food processing environments. This review will discuss some historical aspects of biofilms, possible mechanisms for the adherence of bacteria to surfaces, methods for studying biofilms and problems adherent microorganisms may cause in food processing.
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The cleanability and surface characteristics of various materials commonly used in the dairy industry were assessed by standardized methods. When surface topography was reasonably smooth on a microscopical scale, cleanability differences observed were due to differences in chemical composition.For 304 L stainless steel, we compared cleanability of various industrial finishes in relation to topographical aspects. Surfaces with poor cleanability showed many surface defects. These surfaces are likely to retain more soiling because of increased numbers of attachment sites, a larger soiling/surface contact area and topographical areas in which applied cleaning shear forces are reduced. All surface treatments that reduced the number of topographical defects increased the hygienic qualities of surfaces in comparison to ones which increased surface damage. The most commonly used finish of 304 L stainless steel (2B Glazed steel finished) had the worst topographical aspects and was also the least cleanable.
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The relative surface charge and free energy of forty-one coagulase-negative staphylococci were found to be normally distributed; therefore, they can be considered a homogeneous group under strict statistical criteria. The adherence of these bacteria to eight different biomaterials (seven synthetic and one biologic) was found to be independent of charge and variations in free energy during adhesion. Adherence can be explained as a thermodynamic process (free energy decreased with adherence), except in the case of bovine pericardium in which free energy increases. With these biomaterials, a correlation was found between adherence and bacterial charge. Bacterial adherence and bacterial charge correlate with the surface parameters of the biomaterials. This correlation does not occur when the relationships between parameters are evaluated by means of factors analysis, thus indicating the importance of the statistical method selected for the evaluation of bacterial adherence.
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The influence of human plasma proteins (fibrinogen, albumin and fibronectin) on the adherence of Staphylococcus epidermis to teflon, polyethylene, polycarbonate and bovine pericardium was studied in an in vitro quantitative assay by scintillation counting. Bacterial adhesion was generally reduced by the presence of protein during the adherence assay except in the case of bovine pericardium, in which adherence remained almost unaffected. The effect of these plasma proteins on bacterial surface properties resulted in strong increases of surface charge as measured by ion-exchange chromatography and with no effect on hydrophobicity, estimated as contact angles. Adherence was not found to be correlated with these two properties, suggesting that bacteria-surface interactions must not be simplified to the influence of interfacial forces.
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Bacterial adherence on PE catheters inserted into the carotid artery of rabbits was assessed at 5, 30, and 240 min after injection with bacteria of five coagulase-negative staphylococci (CN Staph). These studies revealed that CN Staph adhere onto PE catheters 5 min after injection with bacteria. At 240 min after injection with bacteria almost all catheters were sterile, indicating that initially adherent bacteria on PE catheters disappear with time. EM studies revealed high numbers of platelets and leukocytes and many fibrin deposits on the surface of the PE catheter. In addition, the adherence of the five test strains on PE catheters was determined in vitro. In these in vitro studies the bacteria and catheters were pretreated with either fibrinogen, fibronectin, albumin or citrated whole plasma or the liquid adherence medium was supplemented with these proteins or the adherence assay was done in citrated whole plasma. The presence of proteins in the adherence medium or pretreatment of the catheter or bacteria with either fibronectin, albumin or whole citrated plasma markedly inhibited bacterial adherence. In contrast, pretreatment of bacteria or both bacteria and catheters with fibrinogen enhanced bacterial adherence suggesting the presence of ligands for fibrinogen on the cell surface of CN Staph.
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The role that bacterial surface hydrophobicity (surface tension) plays in determining the extent of adhesion of polymer substrates and phagocytic ingestion is reviewed. The early attachment phase in bacterial adhesion is shown to depend critically on the relative surface tensions of the three interacting phases; i.e., bacteria, substrate, and suspending liquid surface tension. When suspended in a liquid with a high surface tension such as Hanks balanced salt solution, the most hydrophobic bacteria adhere to all surfaces to the greatest extent. When the liquid surface tension (gamma LV) is larger than the bacterial surface tension (gamma BV), then for any single bacterial species the extent of adhesion decreases with increasing substrate surface tension (gamma SV). When gamma LV less than gamma BV then adhesion increases with increasing gamma SV. Bacterial surface tension also determines in part the extent of phagocytic ingestion and the degree to which antibodies specifically adsorb onto the bacterium resulting in opsonization. The nonspecific adsorption of antibodies results in a considerable modification in the surface properties of the bacteria. Bacterial surface hydrophobicity can be altered significantly through exposure to subinhibitory concentrations of antibiotics, surfactants, lectins, etc. The effect of these changes on subsequent phagocytic ingestion is discussed.
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This chapter describes the strategies that have evolved for measuring cellular surface tensions. It focuses on techniques that are limited to those methods which are applicable to the cellular elements involved in phagocytosis. The surface need not consist of one component but can consist of several components. If these components are uniformly distributed, the surface can be considered homogeneous. In cases where the phase under consideration borders on a second phase, the surface tension for that interface, called the “interfacial tension,” is determined by the nature of these phases. Moreover, as the value of the interfacial tension of—for example, solids—depends on the phase with which the solid is in contact, some reference state must be chosen to be able to compare the surface properties of these solids. However, phagocytic cells and bacteria are usually in an aqueous medium and bringing them to the reference state may cause changes in the structure and the properties of the membrane or the conformation of the protein molecules.
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The effects of hydrophobicities of substrate surfaces on microbial adherence were examined by using Candida albicans and Candida tropicalis and 21 denture base resin materials. With increasing surface free energy of resin plates, increasing adherence of C. albicans and decreasing adherence of C. tropicalis were observed. The surface free energy of C. albicans is higher than that of all resin material surfaces, and C. tropicalis has surface free energy lower than that of all materials used. In calculation of the changes of free energy accompanying the adherence, the higher adherence tendency was accompanied by a lower value for the free energy change in both species. From a different standpoint, the closer the surface free energy of the substrate surface and the microorganism, the higher was the probability of adherence.
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Thirteen strains of lactobacilli were tested for their ability to adhere to commercial devices used in the urinary tract. Although it appeared that the most hydrophilic organisms adhered in highest numbers, there was no significant correlation between water contact angle and adhesiveness to catheters. Five organisms tested were found to be highly adherent to Huggies commercial diapers. Loss in hydrophobicity upon serial culture of Lactobacillus fermentum B-54 was not due to a proteinaceous S layer, although protein involvement per se cannot be ruled out. It was evident that, not only can members of the normal female urogenital flora adhere to commonly used commercial prostheses, but their ability to attach is related to hydrophilic as well as hydrophobic surface components.
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The quality of milk products is threatened by the formation of biofilms of thermophilic streptococci on the internal surfaces of plate heat exchangers used in milk processing. Although attachment to stainless steel surfaces is one of the first stages in the development of a biofilm, the mechanisms involved in attachment have not been reported. The cell surface properties of 12 strains of thermophilic streptococci were examined to determine their importance in attachment to stainless steel surfaces. Hydrophobicity, extracellular polysaccharide production and cell surface charge varied between the different strains but could not be related to numbers attaching. Treating the cells with sodium metaperiodate, lysozyme or trichloroacetic acid to disrupt cell surface polysaccharide had no effect on attachment. Treatment with trypsin or sodium dodecyl sulphate to remove cell surface proteins resulted in a 100-fold reduction in the number of bacteria attaching. This result suggests that the surface proteins of the thermophilic streptococci are important in their attachment to stainless steel.
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Biofilms are a constant concern in food processing environments. Our overall research focus has been to understand the interaction of factors affecting bacterial attachment and biofilm formation with the ultimate goal of devising strategies to control this problem. This paper briefly describes three areas of biofilm research in which we have been involved. Listeria monocytogenes, a foodborne pathogen, survived for prolonged periods on stainless steel and buna-n rubber, materials commonly used in food-processing equipment. Survival was affected by temperature, relative humidity, attachment surface, and soil. Some components in the rubber inhibited growth of the organism on buna-n, which also affected the efficacy of sanitizers on biofilm inactivation. In cheese manufacture, biofilms of Lactobacillus curvatus could lead to a defect caused by the formation of calcium lactate crystals in Cheddar cheese. This hardy organism persisted in low numbers on equipment surfaces and was difficult to eradicate. We investigated the relative contributions and interactions of mechanical, thermal, and chemical processes in an air-injected clean-in-place method for milking systems. Overall, it is important to study the interactions between bacteria and the surfaces in a specific food processing environment to provide more effective measures for prevention of biofilm formation and for its removal.