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Growth Media and Surface Conditioning Influence the Adherence of Pseudomonas fragi, Salmonella typhimurium, and Listeria monocytogenes Cells to Stainless Steel

September 1997
Journal of Food Protection 60(9):1034-1037

DOI:10.4315/0362-028X-60.9.1034

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Microorganisms have been shown to adhere to food-contact surfaces and may provide a route for the contamination of processed food. To better understand this phenomenon, the effects of growth media and surface conditioning on the adherence of Pseudomonas fragi, Salmonella typhimurium and Listeria monocytogenes cells to stainless steel were studied. The microorganisms were grown in tryptic soy broth (TSB), 1% reconstituted skim milk (RSM) and RSM with 1% sucrose (RSM + S). Stainless-steel surfaces were conditioned by immersion in growth media for 1 h and then were rinsed in phosphate-buffered saline (PBS) prior to the adherence assay. After growing in each medium, cells were harvested, resuspended in PBS, and then allowed to contact the stainless steel for 30 min. Adherence was quantified by acridine orange-staining the cells and viewing under epifluorescence microscopy. Growth media had little influence on adherence to stainless steel that had not been preconditioned. P. fragi and L. monocytogenes cells adhered in the highest numbers when grown in RSM plus sucrose. S. typhimurium cells showed the highest level of adherence when grown in TSB. Analysis of variance yielded P values of less than 0.01, indicating that both growth media and surface conditioning were significant in the level of adherence observed.

Concentrations of test microorganisms grown in various test media after centrifuging and resuspending in PBS

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Results of analysis of variance performed on S. typhimurium, L. monocytogenes, and P. fragi cells grown in eitherenced adherence. The results of the ANOVA for each microorganism are shown in Table 2.

…

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1034

Journal of Food Protection, Vol. 60, No.9, 1997, Pages 1034-1037

Growth Media and Surface Conditioning Influence the Adherence

Pseudomonas fragi, Salmonella typhimurium,

and Listeria monocytogenes Cells to Stainless Steel

SCOTT K. HOODt and EDMUND A. ZOTTOLA

Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave., St. Paul, Minnesota 55108, USA

(JFP# 96-216: Received 20 August 1996/Accepted 30 January 1997)

ABSTRACT

Microorganisms have been shown to adhere to food-contact

surfaces and may provide a route for the contamination of

processed food. To better understand this phenomenon, the effects

of growth media and surface conditioning on the adherence of

Pseudomonasfragi, Salmonella typhimurium and Listeria monocy-

togenes cells to stainless steel were studied. The microorganisms

were grown in tryptic soy broth (TSB), 1%reconstituted skim milk

(RSM) and RSM with 1%sucrose (RSM +S). Stainless-steel

surfaces were conditioned by immersion in growth media for I h

and then were rinsed in phosphate-buffered saline (PBS) prior to

the adherence assay. After growing in each medium, cells were

harvested, resuspended in PBS, and then allowed to contact the

stainless steel for 30 min. Adherence was quantified by acridine

orange-staining the cells and viewing under epifluorescence micros-

copy. Growth media had little influence on adherence to stainless

steel that had not been preconditioned. P. fragi and L. monocyto-

genes cells adhered in the highest numbers when grown in RSM

plus sucrose. S. typhimurium cells showed the highest level of

adherencewhengrown inTSB. Analysisof varianceyieldedPvaluesof

lessthan 0.01, indicatingthatboth growthmediaand surfacecondition-

ing were significant in the level of adherence observed.

Key words: Adherence, media effects, surface conditioning

Bacterial attachment in food-processing environments

is a potential source for contamination of foods that may

lead to spoilage and the transmission of food-borne patho-

gens. Microorganisms been shown to attach to chicken

tissue (8), beef, pork, and lamb tissue (1). Adherence to

food-contact surfaces such as stainless steel and rubber has

been demonstrated by a number of researchers

(5,12).

Once cells have attached to food-contact surfaces,

attempts to remove them by traditional cleaning and sanitiz-

ing procedures may be ineffective. Stone and Zottola (11)

used a model clean-in-place (CIP) system to demonstrate

that P.fragi cells may not be removed during the CIP cycle.

Author for correspondence. Tel: 612-624-9274; Fax: 612-625-5272;

E-mail: ezotto1a@che2.che.umn.edu

tPresent address: Kohler Mix Specialities, Inc. White Bear Lake, MN.

Other researchers have shown that adherent L. monocyto-

genes cells exhibited increased resistance to benzalkonium

chloride, anionic acid sanitizer, and heat (2).

In the food-processing environment, stainless-steel sur-

faces come in contact with fluids containing various levels

of food components. One of the first events to occur is the

adsorption of molecules to the surface. This effect is often

referred to as conditioning. The amount of conditioning that

occurs by milk protein has been modeled as a function of

contact-surface tension, temperature, and time, and depend-

ing on the conditions, may provide a better environment for

microbial adherence (6).

The public-health ramifications of contamination by

pathogens such as S. typhimurium and L. monocytogenes are

a major concern of all food processors. Pseudomonas

species are often associated with the spoilage of perishable

foods such as milk and meats and, therefore, have a major

impact on the quality of these foods. The objectives of this

study were to determine the effect of growth conditions and

surface conditioning on the adherence of S. typhimurium, L.

monocytogenes and P.fragi cells to stainless steel.

MATERIALS AND METHODS

Bacterial cultures

S. typhimurium, L. monocytogenes strain V7, and P. fragi

ATCC 4973 were obtained from the culture collection of the

University of Minnesota, Department of Food Science and Nutri-

tion. All cultures were maintained in tryptic soy broth (TSB) (Difco

Laboratories, Detroit, MI) at 4°C. Prior to use, the cultures were

grown in TSB at 22°C and subcultured twice. Bacterial cultures

were grown in the test medium at 22°C for 18 to 24 h.

Test surface and media

The test surface was 304 stainless-steel chips, finish no. 4

by 6 mm). The stainless-steel chips were prepared by rinsing them

in acetone for a minimum of 30 min, rinsing in distilled water, and

then soaking in 1 N NaOH for 1 h. After a final rinse in distilled

water, the chips were allowed to air dry. The chips were sterilized

by autoclaving at 121°C for 15 min in glass jars.

The test media were TSB, 1

reconstituted skim milk (RSM)

(Land O'Lakes, Arden Hills, MN), and 1

reconstituted skim milk

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MEDIA AND SURFACE CONDITIONING INFLUENCE CELL ADHERENCE 1035

FIGURE 1. Number of adherent P. fragi cells observed after 30 min

of contact time with conditioned stainless steel. Growth medium:

_, TSB; ~, RSM; ~, RSM +S.

RSM +S were compared, it was seen that the addition of

sucrose did not enhance growth.

P. fragi cells adhered in substantial numbers under all

conditions tested (Fig. 1). Within each conditioning me-

dium, the greatest P. fragi cell adherence levels were

observed when the culture had been grown in RSM +S.

When the surface was conditioned in PBS, the growth media

did not appear to affect adherence. In addition, when

RSM +S was used as a growth medium, adherence ap-

peared to be enhanced.

S. typhimurium cells also appeared to adhere in high

numbers under all conditions. However, S. typhimurium

cells showed the highest levels of adherence when grown in

TSB (Fig. 2).

L. monocytogenes cells did not adhere in substantial

numbers except under certain conditions. As with S. typhimu-

rium, the highest observed levels of adherence were seen

when L. monocytogenes cells were grown in TSB. Both

growth in and surface conditioning by RSM and RSM +S

appeared to significantly restrict the adherence of L. monocy-

togenes cells to stainless steel (Fig. 3).

Analysis of variance (13) was used to determine if

either growth media or surface-conditioning media influ-

PBS

1% RSM 1% RSM

Sue

Conditioning Medium

TSB

4.0X 105

3.0X 105

6.0X 105

O.OX 100

5.0 X 105

2.0X 105

The concentrations of the microorganisms used in the

adherence assay after resuspending in PBS are shown in

Table 1. Each of the three microorganisms grew to the

highest population in TSB. When growth in RSM and

TABLE 1. Concentrations of test microorganisms grown in various

test media after centrifuging and resuspending in PBS

Test microorganism TSB RSM RSM +S

typhimurium 1.38 X 10

3.70 X 10

4.60 X 10

L. monocytogenes 1.30 X 10

4.9 X 1075.2 X 107

P.fragi 1.30 X 10

4.15 X 1074.10 X 107

Concentration (CPU/ml) in medium

RESULTS

Surface conditioning

To condition the surface, sterile stainless-steel chips were

placed in plastic petri plates containing the conditioning medium.

The chips remained in the medium for 1 h. The medium was

removed and replaced with PBS. The PBS remained for up to 5 min

and was then replaced with the adherence medium.

with 1% sucrose (RSM +S). The conditioning media were TSB,

RSM, RSM +S, and phosphate-buffered saline (PBS). The TSB,

RSM, RSM +S, and PBS were sterilized by autoc1aving at 121

for 15 min.

Quantification of adherence

Pairs of chips were aseptically removed at selected time

intervals. The chips were rinsed by placing them in a section of

silicone tubing (5-mm i.d.) and then pumping sterile 0.1 % peptone

water through the tubing for lOs with a peristaltic pump. The

peptone water was pumped at a rate of 166 ml/min. The chips were

then placed in 10 ml of sterile distilled water. The water was

removed using a vacuum apparatus, and the chips were placed in a

0.025% sterile acridine orange solution (Sigma Chemical Co., St.

Louis, MO) in 0.1 N citrate buffer, pH 6.6, to stain the attached

cells. Following staining, the chips were rinsed in distilled water

and allowed to air dry. Adherent microorganisms were quantified

by viewing the chips using epifluorescence microscopy. Ten fields

of a known area per chip were viewed and the fluorescing cells

were enumerated. The viewing area was determined with the use of

a stage micrometer. A computerized image-analysis system (Global

Lab Image, Data Translation, Maraboro, MA) was used to enumer-

ate the cells. The average number of cells per field was converted to

the number of cells per cm2•

Populations in the test media were determined by plating, in

duplicate, on tryptic soy agar (TSB with 1.5% agar added) (Difco).

The plates for S. typhimurium and L. monocytogenes were incu-

bated at 37

for 24 h and for P.fragi at 23

for 48 h.

Analysis of variance was performed on the data by using the

software MYSTAT (13).

Adherence testing

The cells were harvested from the test cultures grown as

described above by centrifugation and resuspended in PBS. The

cells were then added to the petri plates containing the stainless-

steel chips. Adherence was allowed to occur over 30 min.

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1036

2.0Xl06-

5.0X 105-

O.OX 100-

HOOD AND ZOTIOLA

6.0X 105

5.0 X 105

4.0Xl0S

2.0Xl0S

1.0Xl0S

TSB 1% RSM 1% RSM

Sue

Conditioning Medium

PBS

TSB 1% RSM 1% RSM

Sue PBS

Conditioning Medium

FIGURE 3. Number of adherent L. monocytogenes cells observed

after 30 min of contact time with conditioned stainless steel.

Growth medium: _, TSB; ~, RSM; ~, RSM +

FIGURE 2. Number of adherent S. typhimurium cells observed

after 30 min of contact time with conditioned stainless steel.

Growth medium: _, TSB; ~, RSM; ~, RSM +

TABLE 2.

Results of analysis of variance performed on

typhimurium, L. monocytogenes, and P. fragi cells grown in either

TSB, RSM, or RSM +

and surfaces conditioned in either PBS,

TSB, RSM, or RSM +

Sum of Mean

Species Factor squares

squares Fratio P

typhimurium

Media 1.68 X 1015 28.41 X 1014 98.96 0.00

Conditioning 4.23 X 1015 3 1.41 X 1015 165.81 0.00

Media, conditioning 8.90 X 1914 6 1.48 X 1014 17.45 0.00

L. monocytogenes

Media 3.86 X 1014 2 1.93 X 1014 104.35 0.00

Conditioning 1.96 X 1014 3 6.54 X 1013 35.34 0.00

Media, conditioning 3.84 X 1014 66.40 X 1012 34.55 0.00

P.fragi

Media 1.62 X 1014 28.10 X 1013 22.72 0.00

Conditioning 9.46 X 1013 33.15 X 1013 8.84 0.00

Media, conditioning 2.20 X 1014 6 3.67 X 1013 10.30 0.00

enced adherence. The results of the ANOVA for each

microorganism are shown in Table 2.

DISCUSSION

Surface conditioning by TSB, RSM, or RSM +S

represents the potential of soiling of stainless steel under

food-processing conditions; conditioning in PBS represents

a clean surface. Results of this study show that the effect of

soiling on adherence varied with each microorganism and

each growth medium.

addition to the soiling effect, the

growth conditions also appeared to influence adherence.

Other researchers have observed similar results. Helke et al.

(3) found that exposing both stainless steel and Buna-N to

the individual components of milk inhibited the adherence

of S. typhimurium and L. monocytogenes cells. They also

observed that the attachment menstruum has a significant

effect on attachment. They reported pretreatment with skim

milk and ~-lactoglobulin decreased attachment.

Similar variability in adherence was observed by Speers

and Gilmour

(10).

They studied a variety of microorganisms

originally isolated from milk-soiled surfaces and found that,

in general, when milk components were included in a

suspending medium, adherence was lower than when Ring-

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MEDIA AND SURFACE CONDITIONING INFLUENCE CELL ADHERENCE 1037

er's solution was used as a suspending medium. McGuire (6)

suggested a scenario that might explain the observation that

lower levels of adherence are common when surface is

conditioned with milk. McGuire's model offers the possibil-

ity that adsorbed proteins may establish an equilibrium with

the proteins in the bulk fluid, resulting in a passive surface

that is unable to further adsorb particles such as microorgan-

isms (6).

Marshall et al. (7) hypothesized that bacterial adherence

to surfaces followed a two-step mechanism. The first step

was reversible adherence: cells associated with a surface

could easily be removed. The second step was irreversible

adherence accompanied by extracellular polymers that helped

anchor the cell to the surface. However, other researchers

have found that in the initial step of adherence to a surface,

polymers such as polysaccharides may actually inhibit

adherence. Wrangstadh et al. (15) observed that a marine

Pseudomonas sp. showed a higher level of cell adherence

after starvation. The starvation caused a decrease in the

production of extracellular polysaccharide as observed by

transmission electron microscopy.

In our study, sucrose was added to diluted skim milk for

two reasons. First, it is not uncommon for a dairy to make

sweetened fluid products such as flavored milk and ice

cream mix. Secondly, the addition of sucrose provided

additional carbohydrate for utilization by the bacterial cells

for the production of polysaccharides. P. fragi cells always

adhered in high numbers when grown in 1% RSM +S, while

S. typhimurium cells generally showed a lower adherence

with RSM +S as the growth medium. Polysaccharides do

appear to be involved in the adherence of P. fragi cells to

stainless steel. Herald and Zottola (4) showed that com-

pounds that bind or disrupt carbohydrates tend to decrease

the adherence of P.!ragi to stainless steel.

It is not surprising to see the low adherence of

monocytogenes cells relative to the other microorganisms

tested. Wirtanen and Mattila-Sandholm (14) observed that it

took 5 days for L. monocytogenes to reach 1 X 105cells per

cm2while P.fragi was over 1 X 106cells per cm2after only 2

days. Other researchers have noted that gram-positive

species often adhere at lower levels to inert surfaces such as

glass and stainless steel (10) as well as to meat tissue (1).

Although there were instances in this study that sug-

gested an unclean surface may actually allow fewer cells to

adhere, cleaning is still an essential part of any sanitation

program. It has been shown that L. monocytogenes cells are

much more likely to adhere when growing in the presence of

P. fragi (9). Therefore, when considering cleaning and

sanitizing programs in a food-processing environment, it

must be assumed that a mixed flora is present and in that

mixed flora may be microorganisms that adhere well.

Clearly, microbial adherence to food-contact surfaces

by P. fragi, S. typhimurium, and L. monocytogenes cells is

significantly influenced by both the growth medium and the

conditioning of the surface, as was verified by the statistical

analysis done in this study. With each culture used, Pvalues

of less than 0.01 were obtained (Table 2). These data

indicated that both growth media and surface conditioning

were significant factors affecting the level of adherence

observed. However, there is variability between microorgan-

isms of different species and in the specific conditions that

exist in the food-processing environment. Consequently,

conditions other than those reported here may also influence

microbial adherence in the environment of a food-

processing facility.

ACKNOWLEDGMENTS

Published as paper no. 22579 of the contribution series of the

Minnesota Agricultural Experiment Station conducted under project 18-56

supported by Hatch funds and Funds from the National Livestock and Meat

Board, Chicago, IL.

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Sep 2018

ABSTRACT The ability of many bacteria to adhere to surfaces and form biofilm makes the treatment of infections so difficult and has major consequences in a variety of industries such as food industry. Biofilm generates a persistent cause of contamination, thus, in the present study; inhibition of biofilm formation efficacy of the combination of D-glycin with antibiotics was compared with the antibiotic alone against Escherichia coli biofilm formation. It was found that the synergetic action of antibiotics with D-glycin was effective on inhibition of biofilm formation. The isolates ability to form biofilm was assayed using the tissue culture plate and Congo-red agar methods and findings of this study were source related; since food origin isolates were more biofilm producers when the Congo-red agar used as compared with tissue culture plate method. Minimum inhibitory concentration (MIC) of D-glycin, imipenem and ceftriaxone were determined. The combinations of D-glycin with antibiotics inhibited bacterial biofilm formation more than the antibiotics imipenem and ceftriaxone separately. Susceptibility test to eight antibiotics: Imipenem, ceftriaxone, ampicillin, amoxicilin, cephalexin, clarithromycin, gentamycin and tetracycline; was performed on planktonic cells, and the cells exhibited different sensitivity patterns to them depending on their source.

Effect of combination of D-glycin and antibiotics on biofilm formation by clinical, food and environmental isolates of Escherichia coli

Article

Full-text available

Sep 2018

Multispecies biofilms between Listeria monocytogenes and Listeria innocua with resident microbiota isolated from apple juice processing equipment

Article

Sep 2018
J FOOD SAFETY

When testing conditions that prevail in fruit juice industry it was found that Listeria monocytogenes ATCC 7644 and a wild strain of Listeria innocua were highly hydrophobic, expressed swimming and twitching, co‐aggregated with yeast cells and produced exopolysaccharide, all characteristics that would favor the adhesive process. In mono‐species biofilms, L. innocua adhered on stainless steel at significantly higher counts than L. monocytogenes achieving values of 6.64 ± 0.01 and 5.80 ± 0.21 log CFU/cm². In dual species biofilms with resident yeasts, L. innocua cells counts increase significantly in the presence of Candida tropicalis and Candida krusei and decrease significantly in the presence of Rhodotorula mucilaginosa and Candida kefyr. When cocultured with Candida tropicalis, the cell numbers of L. monocytogenes had a significant increase. These results revealed synergic and antagonistic interactions among species. Practical applications The study supports the plausibility that interactions between L. monocytogenes and members of resident microbiota, such as C. tropicalis, C. krusei, C. kefyr, and R. mucilaginosa, might play an important role for the survival and dissemination of L. monocytogenes. Apple juice processing conditions was used as simulation of the real condition in fruit juice processing environment and these results will alert to fruit juice industry to adopt the best cleaning and disinfecting practices against Listeria.

Teor e composição química do óleo essencial de espécies nativas da família Myrtaceae nos Campos Gerais da Floresta Atlântica do Estado do Paraná

Article

Jan 2016

The Myrtaceae family has great occurrence in Brazil, mainly in the Atlantic Forest of the South and Southeast regions and presents potential for essential oil production. This work aimed to evaluate the essential oil yield and composition of the species Myrciaria delicatula, Campomanesia xantocarpha, Campomanesia aurea, Calyptranthes clusiifolia, Myrcia splendens, Eugenia osoriana, Myrciaria tenella, Myrceugenia reitzii, Calyptranthes concinna e Myrcia arborensis from a segment of the Atlantic Forest of Parana State. The sample collections for essential oil extraction, photographic records and herbarium specimens preparation for botanical species identification were made at the Private Reserve of Natural Heritage (PRNP) Butuguara in Palmeira (PR), with “Campos Gerais” formations. The identification and the official deposit of the species were made at the HFIE Herbarium. The essential oil extraction was carried out by hydrodistillation of fresh and dried leaves using a Clevenger type apparatus and the chemical composition was analyzed by gas phase chromatography coupled with mass spectrometry (GC/MS). Myrceugenia reitzii showed eesential oil yield superior to other species and the essential oil yield of all species increased after drying. The chemical composition in the samples showed mono and sesquiterpenes, being the sesquiterpenes in higher percentages. The drying conditions affected the essential oil composition of the for the majority of the evaluated species.

Effect of combination of D-glycin and antibiotics on biofilm formation by clinical, food and environmental isolates of Escherichia coli

Article

Full-text available

Aug 2016

Marwa H Alkhafaji

The ability of many bacteria to adhere to surfaces and form biofilm makes the treatment of infections so difficult and has major consequences in a variety of industries such as food industry. Biofilm generates a persistent cause of contamination, thus, in the present study; inhibition of biofilm formation efficacy of the combination of D-glycin with antibiotics was compared with the antibiotic alone against Escherichia coli biofilm formation. It was found that the synergetic action of antibiotics with D-glycin was effective on inhibition of biofilm formation. The isolates ability to form biofilm was assayed using the tissue culture plate and Congo-red agar methods and findings of this study were source related; since food origin isolates were more biofilm producers when the Congo-red agar used as compared with tissue culture plate method. Minimum inhibitory concentration (MIC) of D-glycin, imipenem and ceftriaxone were determined. The combinations of D-glycin with antibiotics inhibited bacterial biofilm formation more than the antibiotics imipenem and ceftriaxone separately. Susceptibility test to eight antibiotics: Imipenem, ceftriaxone, ampicillin, amoxicilin, cephalexin, clarithromycin, gentamycin and tetracycline; was performed on planktonic cells, and the cells exhibited different sensitivity patterns to them depending on their source.

Listeria spp. transfers further from boots and wheels across flooring surfaces, compared with Salmonella, in the dairy context

Article

Jun 2023
INT DAIRY J

Surface-adherent Growth of Listeria monocytogenes is Associated with Increased Resistance to Surfactant Sanitizers and Heat

Article

Full-text available

Jul 1990

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.

Attachment of Microorganisms to Pork Skin and Surfaces of Beef and Lamb Carcasses

Article

Full-text available

May 1979

A model system was developed to study attachment to and possibly detachment of bacteria from pork skin and thin-surface slices of beef and lamb carcasses. The technique involves embedding pork skin and beef and lamb surfaces in solidified wax with the skin surface exposed. After exposure of the skin or carcass surface to bacterial suspensions and subsequent manipulations, the sample is removed aseptically from the wax and subjected to agar plate counting methods. A direct relationship existed between bacterial counts of the skin or carcass surface and concentration of bacterial cells in the attachment medium. Much of the bacterial attachment occurred during the first minute of immersion in the attachment medium, although in some instances continued attachment occurred over a 30-min period. Gram-negative motile bacteria showed greater attachment than did gram-positive non-motile species. Temperature and pH of the attachment medium had little effect on the extent of bacterial attachment.

Attachment of Listeria monocytogenes and Salmonella typhimurium to Stainless Steel and Buna-N in the Presence of Milk and Individual Milk Components

Article

Full-text available

Jun 1993

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.

Biofilm Formation by Listeria monocytogenes Utilizes a Primary Colonizing Microorganism in Flowing Systems

Article

Full-text available

Dec 1993

Listeria monocytogenes serotype 3a and Pseudomonas fragi ATCC 4973 were examined for attachment capability and biofilm development on glass coverslips under flowing systems. Tryptic soy broth supplemented with yeast extract was the growth medium. A continuous flow slide chamber was developed for in situ observations using phase-contrast microscopy. Glass coverslips were examined by epifluorescent and scanning electron microscopy for biofilm formation. The ultrastructure of attached test organisms was examined for the presence of exopolymers using transmission electron microscopy. In pure cultures, attachment of L. monocytogenes to glass coverslips was sparse, while P. fragi accumulated on glass coverslips as a confluent layer of cells. When L. monocytogenes was grown in mixed culture with P. fragi, an exopolymer-producing microorganism, attachment and microcolony formation by L. monocytogenes was enhanced. Results suggest that under flowing conditions the presence of an exopolymer-producing microorganism ...

Removal of Foodborne Biofilms - Comparison of Surface and Suspension Tests. Part I

Article

Full-text available

Jan 1992

Some problems encountered in disinfectant testing are presented. Studies were carried out in meat media using the food spoilage microbes Pseudomonas fragi, Bacillus subtilis, Listeria monocytogenes and Enterococcus hirae. Disinfectants were tested against these microbes in suspension and also on steel surfaces where biofilm had been allowed to develop. Comparison of the suspension and surface tests showed that suspension tests do not indicate the susceptibility in practice. The role of the protective glycocalyx developing around bacteria growing on solid surfaces was tested and discussed.

Attachment of Listeria monocytogenes to Stainless Steel, Glass, Polypropylene, and Rubber Surfaces After Short Contact Times

Article

Full-text available

Sep 1990

This study was carried out to investigate the attachment capabilities of Listeria monocytogenes strain Scott A to stainless steel, glass, polypropylene, and rubber surfaces after short contact times at ambient (20 degrees C) and cold storage temperatures (4 degrees C) using scanning electron microscopy technique. Surface energy value of each surface was estimated by contact angle measurements. All surfaces displayed many possible harborages for L. monocytogenes attachment. Our results indicated that L. monocytogenes cells could attach to all surface types at both temperatures after contact times as short as 20 min or 1 h. Extracellular materials could be observed on the surfaces especially polypropylene and glass incubated at 4 and 20 degrees C for 1 h respectively

Mechanism of Initial Event in Sorption of Marine Bacteria to Surfaces

Article

Nov 1971
J Gen Microbiol

The sorption of two marine bacteria to surfaces involved an instantaneous reversible phase, and a time-dependent irreversible phase. Reversible sorption of the non-motile Achromobacter strain R8 decreased to zero as the electrolyte concentration decreased, or as the thickness of the electrical double-layer increased. The electrolyte concentration at which all bacteria were repelled from the glass surface depended on the valency of the cation. The reversible phase is interpreted in terms of the balance between the electrical double-layer repulsion energies at different electrolyte concentrations and the van der Waals attractive energies. Even at the electrolyte concentration of seawater, the bacteria probably are held at a small distance from the glass surface by a repulsion barrier. Reversible sorption often led to rotational motion of the motile Pseudomonas sp. strain R3 at a liquid-glass interface. Pseudomonas R3 produced polymeric fibrils in artificial seawater; these may be concerned in the irreversible sorption of the bacteria to surfaces. Sorption and polymer production were stimulated by 7 mg./l. glucose but higher levels inhibited irreversible sorption. Omission of Ca2+ and Mg2+ from the artificial seawater prevented growth, polymer production, and sorption to surfaces by Pseudomonas R3.

A Predictive Model for Food Particle interactions with Contact Surfaces

Article

Aug 2006
J FOOD SCI

Joseph McGuire

The protein adsorption rate from whole milk onto various surfaces was modeled as a function of contact surface tension, surface temperature, and time. A new kinetic parameter related to the value of contact surface tension which corresponds to a minimal interaction between food components and the solid surface is introduced. This experimentally measurable parameter quantifies the influence of contact surface tension on the activation energy required for irreversible protein adsorption. In spite of its simplicity, the model adequately predicted initial adsorptive behavior under steady flow conditions for a wide range of surface properties.

Effect of Cleaning and Sanitizing on the Attachment of Pseudomonas fragi to Stainless Steel

Article

Jul 1985
J FOOD SCI

The effects of two clean-in-place (CIP) procedures on attachment of Pseudomonas fragi ATCC 4913 to a stainless steel surface were studied using scanning electron microscopy (SEM). Under normal CIP conditions those cells that remained in the system did not exhibit attachment fibrils. Under conditions of lowered detergent water temperature and detergent and sanitizer concentrations, those cells that were present after CIP showed attachment fibrils. Organisms remaining after normal CIP were not viable, whereas those present after suboptimum cleaning were. These viable cells produced attachment fibrils within 24 hr at 21°C and 96 hr at 4°C when grown in milk.

Effect of Various Agents Upon the Attachment of Pseudomonas fragi to Stainless Steel

Article

Mar 1989
J FOOD SCI

Epifluorescent microscopy was used to assay for the effect of selected chemicals and enzymes upon physical attachment of Pseudomonas fragi to stainless steel. The assays were conducted after the pretreatment of cells with the agents, in the presence of agents, and in the removal of attached cells with test agents. Compared to the controls, sodium periodate, cetyltrimethylammonium bromide (Cetavlon), NaOH, and Concanavalin A inhibited the attachment process in the pretreatment and presence assays. Trypsin, sodium dodecyl sulfate (SDS), NaOH and sodium periodate were effective in removing attached cells, while Cetavlon and Triton X-100 stabilized the attachment of cells to the stainless steel surface and prevented their removal. Neither EDTA nor mechanical removal of flagella had a significant effect upon attachment. These results suggested that attachment of P. fragi to stainless steel involved a polysaccharide and protein matrix surrounding the cells.