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Disk prediffusion is a reliable method for testing colistin susceptibility in porcine E. coli strains

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During the last few years, acquired resistance to colistin in Escherichia coli, but also in other bacterial species, has been reported. It has been shown that the disk diffusion test is not a reliable method for the detection of this resistance. Therefore, there is a need for a reliable and cheap test to determine colistin susceptibility of pathogenic E. coli strains. In the current research, the colistin susceptibility of E. coli isolated during the period 2005-2006 from pigs was determined. Results obtained with the Kirby Bauer disk diffusion test (Neosensitabs, Rosco), the disk prediffusion test (Neosensitabs, Rosco) and the E-test (AB Biodisk) were compared with the results of the reference agar dilution assay. The MIC values or inhibition zones showed a bimodal distribution for the results obtained by all test methods, except the disk diffusion assay, suggesting acquired resistance in 15 strains (9.6%). The E-test and disk prediffusion assay generated results within acceptable levels compared to the reference agar dilution assay. The categorical agreement with the results obtained by the agar dilution method were good to very good for all tests, except the disk diffusion assay. In conclusion, current results suggest that, in addition to the E-test, the disk prediffusion test is a reliable, alternative agar-based colistin susceptibility method for testing colistin susceptibility of E. coli isolates in diagnostic bacteriology.
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... Therefore, a more practical method for routine laboratory screening is required (World Health Organization, 2021). Phenotypic detection methods that are still under development have been proposed, such as agar-based screening media (CHROMID ® Colistin R agar, Superpolymyxin ™ , CHROMagar ™ COL-APSE), the Rapid Polymyxin NP test, Colispot, and disc prediffusion (Boyen et al., 2010;Nordmann et al., 2016a;Nordmann et al., 2016b;Abdul Momin et al., 2017;Jouy et al., 2017;Garcia-Fernandez et al., 2019). ...
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Colistin, the last resort for multidrug and extensively drug-resistant bacterial infection treatment, was reintroduced after being avoided in clinical settings from the 1970s to the 1990s because of its high toxicity. Colistin is considered a crucial treatment option for Acinetobacter baumannii and Pseudomonas aeruginosa, which are listed as critical priority pathogens for new antibiotics by the World Health Organization. The resistance mechanisms of colistin are considered to be chromosomally encoded, and no horizontal transfer has been reported. Nevertheless, in November 2015, a transmissible resistance mechanism of colistin, called mobile colistin resistance (MCR), was discovered. Up to ten families with MCR and more than 100 variants of Gram-negative bacteria have been reported worldwide. Even though few have been reported from Acinetobacter spp. and Pseudomonas spp., it is important to closely monitor the epidemiology of mcr genes in these pathogens. Therefore, this review focuses on the most recent update on colistin resistance and the epidemiology of mcr genes among non-fermentative Gram-negative bacilli, especially Acinetobacter spp. and P. aeruginosa.
... In poultry and pig production, colistin has been said to have low frequency of resistance [9]. However, latest discovery revealed that colistin may be losing its clinical efficacy in antimicrobial therapy as Gram-negative bacteria like E. coli have mutated to become resistant to this last resort antibiotics [10]. The possibilities of spread of colistin resistance through horizontal gene transfer contributes to the spread of resistance among closely related bacteria, Enterobacterales family, including E. coli. ...
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Background Antimicrobial resistance (AMR) is a global public health threat and the use of antibiotics growth promoters in food animals has been implicated as a potential contributing factor in the emergence and spread of AMR. This study was conducted to investigate colistin and carbapenem resistance and extended spectrum beta-lactamase producing E. coli from live broiler chicken and chicken meat in Kelantan, Malaysia. Results Among the E. coli isolates, 37.5% (27/72 were positive for at least one of the resistance genes and one isolate was positive for mcr -1, bla TEM-52 , bla NDM and bla OXA-48 whereas 4.17% (3/72) and 2.78% (2/72) were positive for mcr -1, bla TEM-52 and bla OXA -48 , and mcr-1, bla TEM-52 and bla IMP . Multilocus sequence typing (MLST) results revealed the presence of widespread E. coli strains belonging to the sequence types ST410 and ST155 and other extra-intestinal E. coli (ExPEC) strains. Phylogroup A made up the majority 51.85% (14/27) followed by phylogroup B1 22.22% (6/27). Conclusions The findings imply the potential threats of colistin, extended-spectrum beta-lactamase producing and carbapenem resistant E. coli in food animals to the public health and underscores the need for judicious use of antibiotics in animal production and good hygiene practices to curb the rising risks of AMR.
... Traditional strategies to control PWD are centered on antibiotics added to the diet for weaning piglets [5]: colistin (polymixin E) is the most widely used antibiotic against PWD in pigs, alone or combined with other antimicrobials like amoxicillin, given its efficacy and low cost [2]. However, the emergence of colistin-resistant strains in pigs affected by PWD [6,7] is a serious public health concern, since colistin is a last-line therapeutic to treat multidrug resistant Gram-negative bacterial infections in humans [8][9][10]. This concern, together with resistance to other antimicrobials used for the treatment of PWD [11,12], and the general apprehension on antibiotic resistance in livestock and the potential spread to humans, prompted actions to restrict the use of antibiotics in food-producing animals [13], in pigs specifically [5]. ...
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Post-weaning diarrhea (PWD) in pigs has mainly an infectious basis and control strategies are centred on antibiotics added to the diet. Given concerns on the spread of multi-resistant bacteria, it is necessary to develop alternative prophylactic approaches to control PWD in piglets. The most promising alternative strategies are based on substances that act indirectly on the bacteria by stimulating the immune system or by improving gut health. The aim of this study was to evaluate the effect on the gut microbiota of feed supplemented with a mixture of essential oils (garlic and oregano) in weaning piglets, compared to traditional PWD management (in-feed antibiotics) and to a control group without any diet supplementation. The study involved 197 piglets from 18 litters in a single farm. The piglets were followed from birth to day 58 of age and were weaned at day 26. During the experimental period, the animals were monitored for weight and growth, average daily gain, morbidity and mortality. For the metataxonomics analysis, rectal samples were collected from 17 piglets from the three experimental groups at 4 different time-points (days 1, 12, 26 and 58). Results revealed that the gut microbiota in pre- and post-weaning piglets was dominated by the phyla Firmicutes (51%), Bacteroidetes (25%) and Proteobacteria (16%), which together make up for over 90% of the entire piglet core gut microbiota. The core microbiota comprised 10 taxa before weaning and 43 taxa after weaning, with 7 taxa overlapping between timepoints: two of them ( Prevotella 9 , p-value = 0.00095; Solobacterium p-value = 0.00821) were significantly more abundant after weaning. All alpha diversity indexes were significantly different between pre- and post-weaning, while only Shannon and Simpson diversity and equitability were significantly different between treatments. Based on the matrix of Bray-Curtis dissimilarities, samples showed clear clustering per timepoint (before and after weaning, p-value < 0.001) and between treatments by timepoint (p-value = 0.0086). The oil-diet group showed a consistently higher F:B ratio at all timepoints. These results show that the pig gut microbiota changes significantly with weaning, and suggest that the use of essential oils as feed supplementation to control PWD does not seem to alter sgnificantly the microbiota nor the growth parameters of piglets, however modifications of specific taxa may occur.
... Post-Weaning Diarrhoea (PWD) in pigs is globally considered to be the most important economic disease [1]. It is characterized by an increase in mortality, significant weight losses and growth retardation, in combination with increased treatment costs, higher use of antimicrobials and more pronounced batch variation [2- although emergence of antimicrobial resistance in E. coli strains isolated from clinical cases of PWD indicates an urgent need for alternative control strategies [15][16][17][18][19]. ...
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Background: Post-Weaning Diarrhoea (PWD) in pigs is a worldwide economically important disease, which is frequently controlled using antimicrobials. However, emergence of antimicrobial resistance in E. coli strains and new EU regulations urge the need for alternative control measures, such as adapted feeding strategies or immunization. Oral vaccination of suckling piglets using a live non-pathogenic E. coli F4/F18 vaccine was performed in 10 farrow-to-finish sow farms to prevent against post-weaning diarrhoea due to F4-Enterotoxigenic E. coli (ETEC) or F18-ETEC. The vaccination strategy was compared to the standard therapeutic approach in each farm, meanwhile collecting data on Average Daily Weight Gain (ADWG), Feed Conversion Rate (FCR), mortality rate and treatment incidence with antimicrobial drugs (TI100) during the post-weaning period. Results: Vaccine-treated groups demonstrated a significant improvement in FCR, mortality rate and TI100 as compared to the Control group. The ADWG only marginally and non-significantly improved in the Vaccine-treated group. Conclusions: In conclusion, the present study demonstrated the efficacy of an oral live non-pathogenic E. coli F4/F18 vaccine (Coliprotec® F4/F8; Elanco Animal Health) for active immunization of piglets against PWD due to F4-ETEC and F18-ETEC under field conditions. For several economically important performance parameters, such as FCR, mortality rate and TI100, E. coli vaccination performed significantly better as compared to the standard therapeutic approach. Therefore, vaccination against PWD due to F4-ETEC or F18-ETEC using an oral live non-pathogenic E. coli F4/F18 vaccinated may be considered a good alternative to consolidate post-weaning piglet performance results while meeting the new European requirements concerning prudent use of antimicrobials in intensive pig production.
... isolated from cases of PWD urges the need for alternative control measures [14][15][16][17][18]. From the late 1980's onwards, several studies on zinc supply to post-weaned piglets have been performed. ...
... CST is a cyclic heptapeptide consisting of a tripeptide side-chain acylated at the N terminus by a fatty acid tail and has a cationic charge at neutral pH [2]. This antibiotic has been used to control and prevent infectious diseases in animals for decades, but its excessive use has contributed to the emergence of CST-resistant Enterobacteriaceae [3,4], and possibly to the horizontal transmission of CST resistance from farm animals to humans [5]. The plasmid-mediated resistance to CST via carriage mcr-1 was first described in 2016 [6], and has been propagated throughout several countries, becoming a serious pub-lic health problem, especially with the coexistence of other resistance genes such as Extended spectrum beta-lactamases (ESBL) and New Delhi metallo-beta-lactamase (NDM) [7]. ...
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Colistin is a re-emergent antibiotic peptide used as a last resort in clinical practice to overcome multi-drug resistant (MDR) Gram-negative bacterial infections. Unfortunately, the dissemination of colistin-resistant strains has increased in recent years and is considered a public health problem worldwide. Strategies to reduce resistance to antibiotics such as nanotechnology have been applied successfully. In this work, colistin was characterized physicochemically by surface tension measurements. Subsequently, nanoliposomes coated with highly deacetylated chitosan were prepared with and without colistin. The nanoliposomes were characterized using dynamic light scattering and zeta potential measurements. Both physicochemical parameters fluctuated relatively to the addition of col-istin and/or polymer. The antimicrobial activity of formulations increased by four-fold against clinical isolates of susceptible Pseudomona aeruginosa but did not have antimicrobial activity against multidrug-resistant (MDR) bacteria. Interestingly, the free coated nanoliposomes exhibited the same antibacterial activity in both sensitive and MDR strains. Finally, the interaction of colistin with phospholipids was characterized using molecular dynamics (MD) simulations and determined that colistin is weakly associated with micelles constituted by zwitterionic phospholipids.
... The disease is currently controlled using antimicrobials, although the emergence of antimicrobial resistance in E. coli strains isolated from cases of PWD urges the need for alternative control measures [14][15][16][17][18]. ...
... On the other hand, in veterinary medicine, colistin sulfate is indicated for the treatment of Enterobacteriaceae infections and has been widely used as a preventive mass-medication of colibacillosis in piglets [13]. Although colistin is one of the antimicrobial agents with the lowest rates of resistance, the emergence of the mcr-1 (mobile colistin resistant) plasmid in the Enterobacteriaceae population has resulted in the appearance of strains with acquired resistance to this antibiotic [14,15]. In order to stop the increase of colistin-resistant strains, the European Medicines Agency established in 2016 that all EU members should restrict and reduce the use of colistin in animals for treating infections with a target level of 5 mg/PCU, where PCU refers to the 'population correction unit' and takes into account the animal population as well as the estimated weight of each particular animal at the time of treatment with antimicrobials. ...
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Escherichia coli is considered one of the most common agents associated with neonatal diarrhea in piglets. The aim of this work was to characterize the pathogenic and antimicrobial resistance (AMR) profiles of 122 E. coli strains isolated from pigs suffering diarrhea (n = 94) and pigs without diarrhea (n = 28) of 24 farms in Spain. Virulence factors, toxins and AMR (ESBL and colistin) genes and AMR phenotypes of E. coli isolates were analyzed. Low prevalence of pathogenic E. coli strains (26%) was found in both groups. However, ETEC and VTEC strains were more frequently isolated from diarrheic piglets. Irrespectively of diarrhea occurrence, 97.5% of the strains showed a multidrug-resistance (MDR) profile to aminopenicillins, sulfonamides and tetracyclines. It was found that 22% of E. coli was CTX-M+, with CTX-M-14 being the principal allelic variant. Remarkably, 81.5% of CTX-M+ strains were isolated from diarrheic animals and presented an extended MDR profile to aminopenicillins, quinolones and aminoglycosides. Finally, low frequencies of colistin resistance genes mcr-1 (4/122) and mcr-4 (1/122) were found. MDR E. coli strains are circulating in pig farms of Spain, representing a serious threat to animal and public health. More appropriate diagnostic approaches (genetic and AMR phenotypic analysis) should be implemented in animal health to optimize antibiotic treatments.
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Background: Acinetobacter species are leading cause of nosocomial infections, causing significant morbidity and mortality globally including India. Being persistent in the hospital environment and rapidly developing resistance to a wide variety of antibiotics are the most important features of this pathogen. The present study aimed to compare Colistin MIC of Acinetobacter species isolated from the blood samples by E test and Vitek 2 to the standard broth micro dilution test. Methodology: Two antibiotic susceptibility test methods, The Vitek-2 and the E test, against the reference broth micro dilution method in terms of the various parameters such as Reproducibility, reliability, cost and time effectiveness. Data obtained from the current study regarding antimicrobial resistance of Acinetobacter species recovered from clinical specimens referred to microbiology laboratory of SKIMS and was analyzed by using SPSS20.0. Results: Out of 100 isolates of Acinetobacter species analyzed from blood specimens the distribution of Acinetobacter species according to different clinical diagnosis of patients 89% were A. baumannii and 11% were A. lwoffii. Seventy three percent of them were from males and 27% of them were from females with a mean age of 39.6 (SD±27.46). Regarding the specimen and isolate sources, the majority were from ICU (54%), Surgical ward (26%), Medical ward (16%) and 4% from Outpatient department of SKIMS. Significant descending trends of antimicrobial resistance was shown for Amoxicillin/Clavulanic acid, Cefoperazone/ Sulbactam combination, Cotrimoxazole (100%), Levofloxacin (92%) Piperacillin/Tazobactam, Ciprofloxacin (90%), Cephalosporins (>80%), Imipenem and Meropenem (76%), Amikacin (68%), Gentamycin (67%), Tigecycline (11%) and 0% for Colistin respectively. Conclusion: from the study it could be concluded that the best reference method for testing susceptibility to the Polymyxins still remains to be defined. However, in routine clinical practice in most regions worldwide, where a reference method can hardly be implemented, the interpretation of Colistin susceptibility should preferably be based on results of automated systems such as Vitek-2 or the E test. The micro broth Dilution method remains the most reliable and reproducible, however most tedious and time-consuming method. Colistin remains a very effective, least resisted drug for MDR Acinetobacter species as compared by all the three methods. Keywords: Acinetobacter species; Antimicrobial resistance; Colistin; E test and Vitek 2.
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Introduction: Post-weaning diarrhea (PWD) in pigs is a worldwide economically important disease, which is frequently controlled using antibiotics. However, emergence of antimicrobial resistance in Escherichia coli strains urges the need for alternative control measures, such as adapted feeding strategies, pre- and probiotics, organic acids, MCFAs or immunization. Methods: Different alternative control strategies such as active immunization of piglets against PWD with an E. coli F4 vaccine (Coliprotec® F4; Elanco) combined with high energy and protein diets, addition of nutraceuticals (medium chain fatty acids (MCFAs), organic acids and additional fibers) or supplementation of ZnO were evaluated for their efficacy against PWD due to F4 enterotoxigenic E. coli (F4-ETEC) under field conditions. Results: ZnO-supplemented piglets had a lower overall end weight and lower average daily weight gain, as compared to E. coli vaccinated piglets. The E. coli vaccinated group with normal energy and protein diet had the lowest clinical scores, whereas piglets fed a ZnO-supplemented diet had intermediate fecal clinical scores. All E. coli vaccinated groups had a low number of antibiotic treatments. In the nutraceutical group, clinical scores were much higher, indicating more severe clinical diarrhea, which needed additional antibiotic intervention. Conclusions: The present study demonstrated the efficacy of an oral live non-pathogenic E. coli F4 vaccine for active immunization of piglets against PWD due to F4-ETEC under field conditions. Different feeding strategies had no significant effect on the clinical outcome and performance parameters of E. coli vaccinated piglets.
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