scholarly journals Escherichia coli as Commensal and Pathogenic Bacteria among Food-Producing Animals: Health Implications of Extended Spectrum β-Lactamase (ESBL) Production

Animals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2239
Author(s):  
Sónia Ramos ◽  
Vanessa Silva ◽  
Maria de Lurdes Enes Dapkevicius ◽  
Manuela Caniça ◽  
María Teresa Tejedor-Junco ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Bacterial Infections ◽  
Pathogenic Bacteria ◽  
Antimicrobial Agents ◽  
Severe Infection ◽  
Farm Animals ◽  
Neonatal Meningitis ◽  
Salmonella Spp ◽  
E Coli

Escherichia coli are facultative, anaerobic Gram-negative rods with many facets. Within resistant bacterial populations, they play an important ecological role and can be used as a bioindicator of antimicrobial resistance. All animal species used for food production, as well as humans, carry E. coli in their intestinal tracts; plus, the genetic flexibility and adaptability of this bacteria to constantly changing environments allows it to acquire a great number of antimicrobial resistance mechanisms. Thus, the prevalence of antimicrobial resistance in these commensal bacteria (or others, such as enterococci) can be a good indicator for the selective pressure caused by the use of antimicrobial agents, providing an early warning of the emergence of antimicrobial resistance in pathogens. As many as 90% of E. coli strains are commensals inhabiting the intestinal tracts of humans and warm-blooded animals. As a commensal, it lives in a mutually beneficial association with its hosts and rarely causes diseases. However, E. coli also remains as one of the most frequent causes of several common bacterial infections in humans and animals. In humans, it is the prominent cause of enteritis, community- and hospital-acquired urinary tract infection (UTI), septicemia, postsurgical peritonitis, and other clinical infections, such as neonatal meningitis, while, in farm animals, it is more prominently associated with diarrhea. On a global scale, E. coli can be considered the most important human pathogen, causing severe infection along with other major bacterial foodborne agents, such as Salmonella spp. and Campylobacter. Thus, the importance of resistance in E. coli, typically considered a benign commensal, should not be underestimated.

scholarly journals Prevalence of Antimicrobial Resistance (AMR) Salmonella spp. and Escherichia coli Isolated from Broilers in the East Coast of Peninsular Malaysia

Antibiotics ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 579
Author(s):  
Shamsaldeen Ibrahim ◽  
Loh Wei Hoong ◽  
Yip Lai Siong ◽  
Zaharuddin Mustapha ◽  
C. W. Salma C. W. Zalati ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
East Coast ◽  
Peninsular Malaysia ◽  
Control Measures ◽  
Growth Promoters ◽  
Salmonella Spp ◽  
E Coli ◽  
Antimicrobial Susceptibility Tests

Salmonella species (spp.) and Escherichia coli (E. coli) are the most common infectious pathogens in poultry. Antimicrobials are given either as growth promoters or as treatment, thereby increasing the possibility of the emergence of antimicrobial resistance (AMR). We determined the prevalence of AMR for both pathogens isolated from broiler farms in the East Coast of Peninsular Malaysia from 2018–2019. A total of 384 cloacal swabs were collected, followed by bacterial isolation, confirmation, and antimicrobial susceptibility tests. The overall prevalence of Salmonella spp. and E. coli were 6.5% and 51.8%, respectively. Salmonella spp. and E. coli displayed resistance towards the following antimicrobials: erythromycin (100% for both pathogens), chloramphenicol (76.2% and 84.5%, respectively), tetracycline (62% and 94.6%, respectively), ampicillin (47.7% and 87%, respectively), sulfamethoxazole/trimethoprim (42.9% and 83.3%, respectively), ciprofloxacin (4.8% and 23.8%, respectively), nalidixic acid (9.6% and 60.7%, respectively), streptomycin (19% and 66%, respectively), kanamycin (28.6% and 57%, respectively), cephalothin (0% and 11%, respectively), and gentamicin (0% and 20.2%, respectively). Multidrug resistance (MDR) was recorded in 82% of Salmonella spp. and 100% of E. coli. These findings demonstrate the high prevalence of AMR in both pathogens in broiler farms on the East Coast of Peninsular Malaysia. These findings could be attributed to the excessive use of antimicrobial agents by poultry farm owners. Enhanced control measures and a strong monitoring system should be urgently implemented in order to reduce the emergence of antimicrobial resistance.

scholarly journals Prevalence of Antimicrobial Resistance (AMR) Salmonella spp. and Escherichia coli Isolated From Broilers in East Coast Malaysia

2020 ◽  
Author(s):  
Nor Fadhilah Kamaruzzaman ◽  
Shamsaldeen Saeed
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Bacterial Resistance ◽  
Antimicrobial Agents ◽  
East Coast ◽  
Control Measures ◽  
Growth Promoters ◽  
Salmonella Spp ◽  
E Coli ◽  
High Prevalence

Abstract:Salmonella species (spp) and Escherichia coli (E. coli) are the most common infectious pathogens in poultry. Antimicrobials were given either for the treatment or growth promoters that can increase the possibility of emergence of bacterial resistance towards antimicrobials. The aim of this study was to determine the prevalence of antimicrobial resistant (AMR) Salmonella spp and E. coli isolated from a sample of broiler farms in East Coast Malaysia from 2018-2019. A total of 384 cloacal swabs were collected from broilers farms in Kelantan, Terengganu, and Pahang. The bacteria were isolated and confirmed by bacteriological and serological methods. Following that, confirmed isolates were subjected to antimicrobial susceptibility test. Salmonella spp and E. coli were recovered from the cloacal swabs samples with the overall prevalence of 6.5% and 51.8% respectively. In Kelantan, Terengganu and Pahang, the prevalence of Salmonella spp were 7%, 6.5% and 5.8% respectively, while the prevalence for E. coli were 50%, 48.3% and 58% respectively. Salmonella spp and E. coli displayed resistance towards the following antimicrobials: erythromycin (100% for both pathogens), chloramphenicol (76.2%, 84.5%), tetracycline (62%, 94.6%), ampicillin (47.7%, 87%), sulfamethoxazole/trimethoprim (42.9%, 83.3%), ciprofloxacin (4.8%, 23.8%), nalidixic acid (9.6%, 60.7%), streptomycin (19%,66%), and kanamycin (28.6%,57%), cephalotin (0%, 11%), gentamicin (0%, 20.2%) respectively. No resistance were recorded towards colistin for both pathogens. Multidrug resistance (MDR) was recorded in 82% of Salmonella spp and 100% of E. coli. These findings demonstrate the high prevalence of MDR Salmonella spp. and E. coli in broiler farms in East coast Malaysia. This could be attributed to the excessive use of antimicrobial agents by the poultry farm owners. Enhanced control measures and a strong monitoring system should be urgently implemented to reduce the emergence of antimicrobial resistance that is harmful to public health.

scholarly journals Impact of Feed Supplementation with Antimicrobial Agents on Growth Performance of Broiler Chickens, Clostridium perfringens and Enterococcus Counts, and Antibiotic Resistance Phenotypes and Distribution of Antimicrobial Resistance Determinants in Escherichia coli Isolates

2007 ◽  
Vol 73 (20) ◽  
pp. 6566-6576 ◽  
Author(s):  
Moussa S. Diarra ◽  
Fred G. Silversides ◽  
Fatoumata Diarrassouba ◽  
Jane Pritchard ◽  
Luke Masson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Antimicrobial Resistance ◽  
Broiler Chickens ◽  
Antimicrobial Agents ◽  
Growth Promoters ◽  
Feed Supplementation ◽  
E Coli ◽  
Resistance Determinants ◽  
Class 1

ABSTRACT The effects of feed supplementation with the approved antimicrobial agents bambermycin, penicillin, salinomycin, and bacitracin or a combination of salinomycin plus bacitracin were evaluated for the incidence and distribution of antibiotic resistance in 197 commensal Escherichia coli isolates from broiler chickens over 35 days. All isolates showed some degree of multiple antibiotic resistance. Resistance to tetracycline (68.5%), amoxicillin (61.4%), ceftiofur (51.3%), spectinomycin (47.2%), and sulfonamides (42%) was most frequent. The levels of resistance to streptomycin, chloramphenicol, and gentamicin were 33.5, 35.5, and 25.3%, respectively. The overall resistance levels decreased from day 7 to day 35 (P < 0.001). Comparing treatments, the levels of resistance to ceftiofur, spectinomycin, and gentamicin (except for resistance to bacitracin treatment) were significantly higher in isolates from chickens receiving feed supplemented with salinomycin than from the other feeds (P < 0.001). Using a DNA microarray analysis capable of detecting commonly found antimicrobial resistance genes, we characterized 104 tetracycline-resistant E. coli isolates from 7- to 28-day-old chickens fed different growth promoters. Results showed a decrease in the incidence of isolates harboring tet(B), bla TEM, sulI, and aadA and class 1 integron from days 7 to 35 (P < 0.01). Of the 84 tetracycline-ceftiofur-resistant E. coli isolates, 76 (90.5%) were positive for bla CMY-2. The proportions of isolates positive for sulI, aadA, and integron class 1 were significantly higher in salinomycin-treated chickens than in the control or other treatment groups (P < 0.05). These data demonstrate that multiantibiotic-resistant E. coli isolates can be found in broiler chickens regardless of the antimicrobial growth promoters used. However, the phenotype and the distribution of resistance determinants in E. coli can be modulated by feed supplementation with some of the antimicrobial agents used in broiler chicken production.

scholarly journals Genotyping and antimicrobial resistance in Escherichia coli from pig carcasses

2017 ◽  
Vol 37 (11) ◽  
pp. 1253-1260 ◽  
Author(s):  
Caroline Pissetti ◽  
Gabriela Orosco Werlang ◽  
Jalusa Deon Kich ◽  
Marisa Cardoso
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
Commensal Bacteria ◽  
Pfge Analysis ◽  
Gene Detection ◽  
E Coli ◽  
Antimicrobial Resistance Profile ◽  
Resistant Strains ◽  
Pig Carcasses

ABSTRACT: The increasing antimicrobial resistance observed worldwide in bacteria isolated from human and animals is a matter of extreme concern and has led to the monitoring of antimicrobial resistance in pathogenic and commensal bacteria. The aim of this study was to evaluate the antimicrobial resistance profile of Escherichia coli isolated from pig carcasses and to assess the occurrence of relevant resistance genes. A total of 319 E. coli isolates were tested for antimicrobial susceptibility against different antimicrobial agents. Moreover, the presence of extended-spectrum β-lactamase (ESBL) and inducible ampC-β-lactamase producers was investigated. Eighteen multi-resistant strains were chosen for resistance gene detection and PFGE characterization. The study showed that resistance to antimicrobials is widespread in E. coli isolated from pig carcasses, since 86.2% of the strains were resistant to at least one antimicrobial and 71.5% displayed multi-resistance profiles. No ampC-producing isolates were detected and only one ESBL-producing E. coli was identified. Genes strA (n=15), floR (n=14), aac(3)IVa (n=13), tetB (n=13), sul2 (n=12), tetA (n=11), aph(3)Ia (n=8) and sul3 (n=5) were detected by PCR. PFGE analysis of these multi-resistant E. coli strains showed less than 80% similarity among them. We conclude that antimicrobial multi-resistant E. coli strains are common on pig carcasses and present highly diverse genotypes and resistance phenotypes and genotypes.

scholarly journals Multi-omic surveillance of Escherichia coli and Klebsiella spp. in hospital sink drains and patients

2020 ◽  
Author(s):  
B Constantinides ◽  
KK Chau ◽  
TP Quan ◽  
G Rodger ◽  
M Andersson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Resistance Genes ◽  
Bacterial Infections ◽  
Wide Spectrum ◽  
Klebsiella Oxytoca ◽  
Clinical Disease ◽  
E Coli ◽  
Antimicrobial Resistance Genes ◽  
Wide Range

ABSTRACTEscherichia coli and Klebsiella spp. are important human pathogens that cause a wide spectrum of clinical disease. In healthcare settings, sinks and other wastewater sites have been shown to be reservoirs of antimicrobial-resistant E. coli and Klebsiella spp., particularly in the context of outbreaks of resistant strains amongst patients. Without focusing exclusively on resistance markers or a clinical outbreak, we demonstrate that many hospital sink drains are abundantly and persistently colonised with diverse populations of E. coli, Klebsiella pneumoniae and Klebsiella oxytoca, including both antimicrobial-resistant and susceptible strains. Using whole genome sequencing (WGS) of 439 isolates, we show that environmental bacterial populations are largely structured by ward and sink, with only a handful of lineages, such as E. coli ST635, being widely distributed, suggesting different prevailing ecologies which may vary as a result of different inputs and selection pressures. WGS of 46 contemporaneous patient isolates identified one (2%; 95% CI 0.05-11%) E. coli urine infection-associated isolate with high similarity to a prior sink isolate, suggesting that sinks may contribute to up to 10% of infections caused by these organisms in patients on the ward over the same timeframe. Using metagenomics from 20 sink-timepoints, we show that sinks also harbour many clinically relevant antimicrobial resistance genes including blaCTX-M, blaSHV and mcr, and may act as niches for the exchange and amplification of these genes. Our study reinforces the potential role of sinks in contributing to Enterobacterales infection and antimicrobial resistance in hospital patients, something that could be amenable to intervention.IMPORTANCEEscherichia coli and Klebsiella spp. cause a wide range of bacterial infections, including bloodstream, urine and lung infections. Previous studies have shown that sink drains in hospitals may be part of transmission chains in outbreaks of antimicrobial-resistant E. coli and Klebsiella spp., leading to colonisation and clinical disease in patients. We show that even in non-outbreak settings, contamination of sink drains by these bacteria is common across hospital wards, and that many antimicrobial resistance genes can be found and potentially exchanged in these sink drain sites. Our findings demonstrate that the colonisation of handwashing sink drains by these bacteria in hospitals is likely contributing to some infections in patients, and that additional work is needed to further quantify this risk, and to consider appropriate mitigating interventions.

scholarly journals Molecular characterisation of antimicrobial resistance and virulence genes in Escherichia coli strains isolated from diarrhoeic and healthy rabbits in Tunisia

2020 ◽  
Vol 28 (2) ◽  
pp. 81
Author(s):  
Raouia Ben Rhouma ◽  
Ahlem Jouini ◽  
Amira Klibi ◽  
Safa Hamrouni ◽  
Aziza Boubaker ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Virulence Genes ◽  
Antimicrobial Agents ◽  
Antibiotic Resistance Genes ◽  
Virulence Gene ◽  
Diffusion Method ◽  
Class 1 Integron ◽  
E Coli ◽  
Class 1

The purpose of this study was to identify <em>Escherichia coli</em> isolates in diarrhoeic and healthy rabbits in Tunisia and characterise their virulence and antibiotic resistance genes. In the 2014-2015 period, 60 faecal samples from diarrhoeic and healthy rabbits were collected from different breeding farms in Tunisia. Susceptibility to 14 antimicrobial agents was tested by disc diffusion method and the mechanisms of gene resistance were evaluated using polymerase chain reaction and sequencing methods. Forty <em>E. coli</em> isolates were recovered in selective media. High frequency of resistance to tetracycline (95%) was detected, followed by different levels of resistance to sulphonamide (72.5%), streptomycin (62.5%), trimethoprim-sulfamethoxazole (60%), nalidixic acid (32.5%), ampicillin (37.5%) and ticarcillin (35%). <em>E. coli</em> strains were susceptible to cefotaxime, ceftazidime and imipenem. Different variants of bla<sub>TEM</sub>, <em>tet</em>, <em>sul</em> genes were detected in most of the strains resistant to ampicillin, tetracycline and sulphonamide, respectively. The presence of class 1 integron was studied in 29 sulphonamide-resistant <em>E. coli</em> strains from which 15 harboured class 1 integron with four different arrangements of gene cassettes, <em>dfrA17</em>+<em>aadA5</em> (n=9), <em>dfrA1</em> + <em>aadA1</em> (n=4), <em>dfrA12</em> + <em>addA2</em> (n=1), <em>dfrA12</em>+<em>orf</em>+<em>addA2</em> (n=1). The <em>qnrB</em> gene was detected in six strains out of 13 quinolone-resistant <em>E. coli</em> strains. Seventeen <em>E. coli</em> isolates from diarrhoeic rabbits harboured the enteropathogenic eae genes associated with different virulence genes tested (<em>fimA</em>, <em>cnf1</em>, <em>aer</em>), and affiliated to B2 (n=8) and D (n=9) phylogroups. Isolated <em>E. coli</em> strains from healthy rabbit were harbouring <em>fim A</em> and/or <em>cnf1</em> genes and affiliated to A and B1 phylogroups. This study showed that <em>E. coli</em> strains from the intestinal tract of rabbits are resistant to the widely prescribed antibiotics in medicine. Therefore, they constitute a reservoir of antimicrobial-resistant genes, which may play a significant role in the spread of antimicrobial resistance. In addition, the eae virulence gene seemed to be implicated in diarrhoea in breeder rabbits in Tunisia.

scholarly journals d-Serine induces distinct transcriptomes in diverse Escherichia coli pathotypes

Microbiology ◽  
2021 ◽  
Vol 167 (10) ◽  
Author(s):  
James P. R. Connolly ◽  
Natasha C. A. Turner ◽  
Jennifer C. Hallam ◽  
Patricia T. Rimbi ◽  
Tom Flett ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Type Species ◽  
Pathogenic Bacteria ◽  
Neonatal Meningitis ◽  
Published Data ◽  
Toxic Metabolite ◽  
Transcriptional Responses ◽  
Content Type ◽  
E Coli ◽  
Link Type

Appropriate interpretation of environmental signals facilitates niche specificity in pathogenic bacteria. However, the responses of niche-specific pathogens to common host signals are poorly understood. d-Serine (d-ser) is a toxic metabolite present in highly variable concentrations at different colonization sites within the human host that we previously found is capable of inducing changes in gene expression. In this study, we made the striking observation that the global transcriptional response of three Escherichia coli pathotypes – enterohaemorrhagic E. coli (EHEC), uropathogenic E. coli (UPEC) and neonatal meningitis-associated E. coli (NMEC) – to d-ser was highly distinct. In fact, we identified no single differentially expressed gene common to all three strains. We observed the induction of ribosome-associated genes in extraintestinal pathogens UPEC and NMEC only, and the induction of purine metabolism genes in gut-restricted EHEC, and UPEC indicating distinct transcriptional responses to a common signal. UPEC and NMEC encode dsdCXA – a genetic locus required for detoxification and hence normal growth in the presence of d-ser. Specific transcriptional responses were induced in strains accumulating d-ser (WT EHEC and UPEC/NMEC mutants lacking the d-ser-responsive transcriptional activator DsdC), corroborating the notion that d-ser is an unfavourable metabolite if not metabolized. Importantly, many of the UPEC-associated transcriptome alterations correlate with published data on the urinary transcriptome, supporting the hypothesis that d-ser sensing forms a key part of urinary niche adaptation in this pathotype. Collectively, our results demonstrate distinct pleiotropic responses to a common metabolite in diverse E. coli pathotypes, with important implications for niche selectivity.

Comparing antibiotic resistance in commensal and pathogenic bacteria isolated from wild-caught South Carolina shrimps vs. farm-raised imported shrimps

2007 ◽  
Vol 53 (7) ◽  
pp. 919-924 ◽  
Author(s):  
Kavitha Boinapally ◽  
Xiuping Jiang
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
South Carolina ◽  
Antimicrobial Resistance ◽  
Pathogenic Bacteria ◽  
Vibrio Vulnificus ◽  
Resistant Bacteria ◽  
Microbiological Analysis ◽  
Salmonella Spp ◽  
Plate Counts

The objective of this study was to assess and differentiate wild-caught South Carolina (SC) shrimps from imported shrimps on the basis of microbiological analysis. Seven wild-caught SC shrimp and 13 farm-raised imported shrimp samples were analyzed. Total plate counts from wild-caught shrimp samples ranged from 4.3 to 7.0 log10 CFU/g, whereas counts from imported shrimp samples ranged from 3.2 to 5.7 log10 CFU/g. There was no difference (P > 0.05) between total bacterial counts of wild-caught SC shrimp and farm-raised imported shrimp. However, the percentages of bacteria with reduced susceptibility towards ceftriaxone and tetracycline were higher (P < 0.05) for farm-raised shrimp than for wild-caught samples. Salmonella spp. detected only in one farm-raised sample was resistant to ampicillin, ceftriaxone, gentamicin, streptomycin, and trimethoprim. Vibrio vulnificus was detected in both wild-caught and farm-raised shrimp samples; however, only the isolate from farm-raised shrimp was resistant to nalidixic acid and trimethoprim. Escherichia coli detected in one wild-caught sample was resistant to ampicillin. Both Listeria spp. and Salmonella spp. were absent with wild-caught SC samples. Therefore, the presence of more ceftriaxone- and tetracycline-resistant bacteria and the observed antimicrobial resistance phenotypes of isolates from the imported shrimp may reflect the possible use of antibiotics in raising shrimp in those countries.

Antimicrobial Resistance and Association with Class 1 Integrons in Escherichia coli Isolated from Turkey Meat Products

2008 ◽  
Vol 71 (8) ◽  
pp. 1679-1684 ◽  
Author(s):  
M. L. KHAITSA ◽  
J. OLOYA ◽  
D. DOETKOTT ◽  
R. KEGODE
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
Population Attributable Fraction ◽  
Meat Products ◽  
Resistance Mechanisms ◽  
E Coli ◽  
Class 1 Integrons ◽  
Turkey Meat ◽  
Class 1

The objective of this study was to quantify the role of class 1 integrons in antimicrobial resistance in Escherichia coli isolated from turkey meat products purchased from retail outlets in the Midwestern United States. Of 242 E. coli isolates, 41.3% (102 of 242) tested positive for class 1 integrons. A significant association was shown between presence of class 1 integrons in E. coli isolates and the resistance to tetracycline, ampicillin, streptomycin, gentamicin, sulfisoxazole, and trimethoprim-sulfamethoxazole. Attributable risk analysis revealed that for every 100 E. coli isolates carrying class 1 integrons, resistance was demonstrated for ampicillin (22%), gentamycin (48%), streptomycin (29%), sulfisoxazole (40%), trimethoprimsulfamethoxazole (7%), and tetracycline (26%). Non–integron-related antimicrobial resistance was demonstrated for ampicillin (65%), gentamycin (16.9%), streptomycin (42.1%), sulfisoxazole (35.8%), and tetracycline (49.7%). Population-attributable fraction analysis showed that class 1 integrons accounted for the following resistances: gentamycin, 71% (50 of 71), amoxicillin–clavulanic acid, 19.6% (6 of 33), nalidixic acid, 34% (7 of 21), streptomycin, 28% (30 of 107), sulfisoxazole, 38% (40 of 106), and tetracycline, 14%, (26 of 185). In conclusion, although class 1 integrons have been implicated in resistance to antimicrobial agents, other non–integron resistance mechanisms seem to play an important part.

Detection of Multiple-Antimicrobial Resistance and Characterization of the Implicated Genes in Escherichia coli Isolates from Foods of Animal Origin in Tunis

2009 ◽  
Vol 72 (5) ◽  
pp. 1082-1088 ◽  
Author(s):  
AHLEM JOUINI ◽  
KARIM BEN SLAMA ◽  
YOLANDA SÁENZ ◽  
NAOUEL KLIBI ◽  
DANIELA COSTA ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
Food Samples ◽  
Animal Origin ◽  
E Coli ◽  
Antimicrobial Resistance Genes ◽  
Class 1 ◽  
Agar Dilution

Phenotypic and genotypic characterization of antimicrobial resistance was conducted for 98 Escherichia coli isolates recovered from 40 food samples of animal origin (poultry, sheep, beef, fish, and others) obtained in supermarkets and local butcheries in Tunis during 2004 and 2005. Susceptibility to 15 antimicrobial agents was tested by disk diffusion and agar dilution methods, the mechanisms of resistance were evaluated using PCR and sequencing methods, and the clonal relationship among isolates was evaluated using pulsed-field gel electrophoresis. High resistance was detected to tetracycline, sulphonamides, nalidixic acid, ampicillin, streptomycin, and trimethoprim-sulfamethoxazole (29 to 43% of isolates), but all isolates were susceptible to cefotaxime, ceftazidime, cefoxitin, azthreonam, and amikacin. One-third of the isolates had multiresistant phenotypes (resistance to at least five different families of antimicrobial agents). Different variants of blaTEM, tet, sul, dfrA, aadA, and aac(3) genes were detected in most of the strains resistant to ampicillin, tetracycline, sulphonamide, trimethoprim, streptomycin, and gentamicin, respectively. The presence of class 1 and class 2 integrons was studied in 15 sulphonamide-resistant unrelated E. coli strains, and 14 of these strains harbored class 1 integrons with five different arrangements of gene cassettes, and a class 2 integron with the dfrA1 + sat + aadA1 arrangement was found in one strain. This study revealed the high diversity of antimicrobial resistance genes, some of them included in integrons, in E. coli isolates of food origin.

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