scholarly journals Effect of diet modification in intestinal Escherichia coli population and antimicrobial resistance

2021 ◽  
Author(s):  
Maria Fernanda Loayza Villa ◽  
Daniela Garcia ◽  
Alejandro Torres ◽  
Gabriel Trueba
Keyword(s):  
Antimicrobial Resistance ◽  
Turnover Rate ◽  
Susceptibility Testing ◽  
Diet Change ◽  
High Turnover ◽  
E Coli ◽  
Antimicrobial Resistance Genes ◽  
Bacterial Mutants ◽  
Taxon Composition ◽  
High Diversity

The fluctuations in the number of some intestinal bacterial lineages may be associated with increased antimicrobial resistance and disease. Adaptation to a given environment may select bacterial mutants that have reduced ability to adapt to new environments and changes in diet have been associated with alterations in microbiome taxon composition. We wanted to see the effect of diet change in linage composition and antimicrobial resistance profiles of numerically dominant E. coli. We subjected 50 chickens from an industrial operation (under corn-based diet supplemented with antimicrobials) to 2 antimicrobial-free diets; one based on corn and the other based on alfalfa. Fecal samples were obtained from all animals at arrival and after five weeks under different diets. Five E. coli colonies (from each sample) were subjected to genetic typing and antimicrobial susceptibility testing. We observed high diversity and high turnover rate of numerically dominant E. coli strains from animals from both diet groups. We did not find differences in antimicrobial resistance profiles in isolates from different diet groups. Our results suggest that there is high diversity and high turnover rate of E. coli strains in the intestines regardless of the diet. Chicken intestines seemed to contain many E. coliThe fluctuations in the number of some intestinal bacterial lineages may be associated with increased antimicrobial resistance and disease. Adaptation to a given environment may select bacterial mutants that have reduced ability to adapt to new environments and changes in diet have been associated with alterations in microbiome taxon composition. We wanted to see the effect of diet change in linage composition and antimicrobial resistance profiles of numerically dominant E. coli. We subjected 50 chickens from an industrial operation (under corn-based diet supplemented with antimicrobials) to 2 antimicrobial-free diets; one based on corn and the other based on alfalfa. Fecal samples were obtained from all animals at arrival and after five weeks under different diets. Five E. coli colonies (from each sample) were subjected to genetic typing and antimicrobial susceptibility testing. We observed high diversity and high turnover rate of numerically dominant E. coli strains from animals from both diet groups. We did not find differences in antimicrobial resistance profiles in isolates from different diet groups. Our results suggest that there is high diversity and high turnover rate of E. coli strains in the intestines regardless of the diet. Chicken intestines seemed to contain many E. coli lineages able to thrive in different substrates. The absence of differences in antimicrobial resistance among bacteria, from animals in different diets, may indicate that the carriage of antimicrobial resistance genes does not affect the bacterial ability to adapt to different substrates. lineages able to thrive in different substrates. The absence of differences in antimicrobial resistance among bacteria, from animals in different diets, may indicate that the carriage of antimicrobial resistance genes does not affect the bacterial ability to adapt to different substrates.

scholarly journals Antimicrobial Resistance of Escherichia coli and Pseudomonas aeruginosa from Companion Birds

Antibiotics ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 780
Author(s):  
Lorena Varriale ◽  
Ludovico Dipineto ◽  
Tamara Pasqualina Russo ◽  
Luca Borrelli ◽  
Violante Romano ◽  
...  
Keyword(s):  
Public Health ◽  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
One Health ◽  
Susceptibility Testing ◽  
Health Concern ◽  
Bacterial Strains ◽  
Public Health Concern ◽  
E Coli ◽  
Antimicrobial Resistance Genes

Antimicrobial resistance is a public health concern worldwide and it is largely attributed to the horizontal exchange of transferable genetic elements such as plasmids carrying integrons. Several studies have been conducted on livestock showing a correlation between the systemic use of antibiotics and the onset of resistant bacterial strains. In contrast, although companion birds are historically considered as an important reservoir for human health threats, little information on the antimicrobial resistance in these species is available in the literature. Therefore, this study was aimed at evaluating the antimicrobial resistance of Escherichia coli and Pseudomonasaeruginosa isolated from 755 companion birds. Cloacal samples were processed for E. coli and P. aeruginosa isolation and then all isolates were submitted to antimicrobial susceptibility testing. P. aeruginosa was isolated in 59/755 (7.8%) samples, whereas E. coli was isolated in 231/755 (30.7%) samples. Most strains showed multidrug resistance. This study highlights that companion birds may act as substantial reservoirs carrying antimicrobial resistance genes which could transfer directly or indirectly to humans and animals, and from a One Health perspective this risk should not be underestimated.

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 Investigation of the Genes Involved in the Outbreaks of Escherichia coli and Salmonella spp. in the United States

Antibiotics ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1274
Author(s):  
Michelle Li ◽  
Kyle Wang ◽  
Ashley Tang ◽  
Aaron Tang ◽  
Andrew Chen ◽  
...  
Keyword(s):  
Stress Response ◽  
Antimicrobial Resistance ◽  
Pathogen Detection ◽  
Dimensional Space ◽  
Virulence Gene ◽  
Principal Component ◽  
The United States ◽  
Salmonella Spp ◽  
E Coli ◽  
Antimicrobial Resistance Genes

Salmonella spp. and Escherichiacoli (E. coli) are two of the deadliest foodborne pathogens in the US. Genes involved in antimicrobial resistance, virulence, and stress response, enable these pathogens to increase their pathogenicity. This study aims to examine the genes detected in both outbreak and non-outbreak Salmonella spp. and E. coli by analyzing the data from the National Centre for Biotechnology Information (NCBI) Pathogen Detection Isolates Browser database. A multivariate statistical analysis was conducted on the genes detected in isolates of outbreak Salmonella spp., non-outbreak Salmonella spp., outbreak E. coli, and non-outbreak E. coli. The genes from the data were projected onto a two-dimensional space through principal component analysis. Hierarchical clustering was then used to quantify the relationship between the genes in the dataset. Most of the outlier genes identified in E. coli isolates are virulence genes, while outlier genes identified in Salmonella spp. are mainly involved in stress response. Gene epeA, which encodes a high-molecular-weight serine protease autotransporter of Enterobacteriaceae (SPATE) protein, along with subA and subB that encode cytotoxic activity, may contribute to the pathogenesis of outbreak E. coli. The iro operon and ars operon may play a role in the ecological success of the epidemic clones of Salmonella spp. Concurrent relationships between esp and ter operons in E. coli and pco and sil operons in Salmonella spp. are found. Stress-response genes (asr, golT, golS), virulence gene (sinH), and antimicrobial resistance genes (mdsA and mdsB) in Salmonella spp. also show a concurrent relationship. All these findings provide helpful information for experiment design to combat outbreaks of E. coli and Salmonella spp.

scholarly journals Antimicrobial resistance pattern of extended-spectrum β-lactamase-producing Escherichia coli isolated from fecal samples of piglets and pig farm workers of selected organized farms of India

2020 ◽  
Vol 13 (2) ◽  
pp. 360-363
Author(s):  
Shikha Tamta ◽  
Obli Rajendran Vinodh Kumar ◽  
Shiv Varan Singh ◽  
Bommenahalli Siddaramiah Pruthvishree ◽  
Ravichandran Karthikeyan ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Susceptibility Testing ◽  
Farm Workers ◽  
Resistance Pattern ◽  
Antibiotic Susceptibility Testing ◽  
M Gene ◽  
Fecal Samples ◽  
E Coli ◽  
Pig Farm

Background and Aim: Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli are gradually increasing worldwide and carry a serious public threat. This study aimed to determine the antimicrobial resistance pattern of ESBL-producing E. coli isolated from fecal samples of piglets and pig farm workers. Materials and Methods: Fecal samples from <3-month-old piglets (n=156) and farm workers (n=21) were processed for the isolation of ESBL-producing E. coli in MacConkey agar added with 1 μg/mL of cefotaxime. E. coli (piglets=124; farm workers=21) were tested for ESBL production by combined disk method and ESBL E-strip test. Each of the ESBL-positive isolate was subjected to antibiotic susceptibility testing. The ESBL-producing E. coli were further processed for genotypic confirmation to CTX-M gene. Results: A total of 55 (44.4%, 55/124) and nine (42.9%, 9/21) ESBL-producing E. coli were isolated from piglets and farm workers, respectively. Antibiotic susceptibility testing of the ESBL-positive E. coli isolates from piglets and farm workers showed 100% resistance to ceftazidime, cefotaxime, cefotaxime/clavulanic acid, ceftazidime/clavulanic acid, and cefpodoxime. A proportion of 100% (55/55) and 88.9% (8/9) ESBL-positive E. coli were multidrug resistance (MDR) in piglets and farm workers, respectively. On genotypic screening of the ESBL E. coli isolated from piglets (n=55), 15 were positive for the blaCTX-M gene and of the nine ESBL E. coli from farm workers, none were positive for the blaCTX-M gene. Conclusion: Although there was no significant difference in isolation of ESBL-producing E. coli between piglets and farm workers, the ESBL-positive E. coli from piglets showed relatively higher MDR than farm workers.

scholarly journals Impact of UV and Peracetic Acid Disinfection on the Prevalence of Virulence and Antimicrobial Resistance Genes in Uropathogenic Escherichia coli in Wastewater Effluents

2014 ◽  
Vol 80 (12) ◽  
pp. 3656-3666 ◽  
Author(s):  
Basanta Kumar Biswal ◽  
Ramzi Khairallah ◽  
Kareem Bibi ◽  
Alberto Mazza ◽  
Ronald Gehr ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Resistance Genes ◽  
Peracetic Acid ◽  
Content Type ◽  
E Coli ◽  
Antimicrobial Resistance Genes ◽  
Antimicrobial Resistance Gene ◽  
Municipal Wastewaters ◽  
The Impact

ABSTRACTWastewater discharges may increase the populations of pathogens, includingEscherichia coli, and of antimicrobial-resistant strains in receiving waters. This study investigated the impact of UV and peracetic acid (PAA) disinfection on the prevalence of virulence and antimicrobial resistance genes in uropathogenicEscherichia coli(UPEC), the most abundantE. colipathotype in municipal wastewaters. Laboratory disinfection experiments were conducted on wastewater treated by physicochemical, activated sludge, or biofiltration processes; 1,766E. coliisolates were obtained for the evaluation. The target disinfection level was 200 CFU/100 ml, resulting in UV and PAA doses of 7 to 30 mJ/cm2and 0.9 to 2.0 mg/liter, respectively. The proportions of UPECs were reduced in all samples after disinfection, with an average reduction by UV of 55% (range, 22% to 80%) and by PAA of 52% (range, 11% to 100%). Analysis of urovirulence genes revealed that the decline in the UPEC populations was not associated with any particular virulence factor. A positive association was found between the occurrence of urovirulence and antimicrobial resistance genes (ARGs). However, the changes in the prevalence of ARGs in potential UPECs were different following disinfection, i.e., UV appears to have had no effect, while PAA significantly reduced the ARG levels. Thus, this study showed that both UV and PAA disinfections reduced the proportion of UPECs and that PAA disinfection also reduced the proportion of antimicrobial resistance gene-carrying UPEC pathotypes in municipal wastewaters.

Antimicrobial Resistance in Campylobacter, Salmonella, and Escherichia coli Isolated from Retail Grain-Fed Veal Meat from Southern Ontario, Canada

2011 ◽  
Vol 74 (8) ◽  
pp. 1245-1251 ◽  
Author(s):  
ANGELA COOK ◽  
RICHARD J. REID-SMITH ◽  
REBECCA J. IRWIN ◽  
SCOTT A. McEWEN ◽  
VIRGINIA YOUNG ◽  
...  
Keyword(s):  
Public Health ◽  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Tetracycline Resistance ◽  
Antimicrobial Susceptibility Testing ◽  
E Coli ◽  
Testing Resistance ◽  
Resistance Patterns

This study estimated the prevalence of Salmonella, Campylobacter, and Escherichia coli isolates in fresh retail grain-fed veal obtained in Ontario, Canada. The prevalence and antimicrobial resistance patterns were examined for points of public health significance. Veal samples (n = 528) were collected from February 2003 through May 2004. Twenty-one Salmonella isolates were recovered from 18 (4%) of 438 samples and underwent antimicrobial susceptibility testing. Resistance to one or more antimicrobials was found in 6 (29%) of 21 Salmonella isolates; 5 (24%) of 21 isolates were resistant to five or more antimicrobials. No resistance to antimicrobials of very high human health importance was observed. Ampicillin-chloramphenicol-streptomycin-sulfamethoxazole-tetracycline resistance was found in 5 (3%) of 21 Salmonella isolates. Campylobacter isolates were recovered from 5 (1%) of 438 samples; 6 isolates underwent antimicrobial susceptibility testing. Resistance to one or more antimicrobials was documented in 3 (50%) of 6 Campylobacter isolates. No Campylobacter isolates were resistant to five or more antimicrobials or category I antimicrobials. E. coli isolates were recovered from 387 (88%) of 438 samples; 1,258 isolates underwent antimicrobial susceptibility testing. Resistance to one or more antimicrobials was found in 678 (54%) of 1,258 E. coli isolates; 128 (10%) of 1,258 were resistant to five or more antimicrobials. Five (0.4%) and 7 (0.6%) of 1,258 E. coli isolates were resistant to ceftiofur and ceftriaxone, respectively, while 34 (3%) of 1,258 were resistant to nalidixic acid. Ciprofloxacin resistance was not detected. There were 101 different resistance patterns observed among E. coli isolates; resistance to tetracycline alone (12.7%, 161 of 1,258) was most frequently observed. This study provides baseline prevalence and antimicrobial resistance data and highlights potential public health concerns.

Virulence and antimicrobial resistance genes associated with the in-vivo pathogenicity of avian pathogenic E. coli isolates

2021 ◽  
Vol 1 (1) ◽  
pp. 17-20
Author(s):  
Ahmed Abd El-Mawgoud ◽  
Azza El-Sawah ◽  
Soad Nasef ◽  
Al-Hussien Dahshan ◽  
Ahmed Ali
Keyword(s):  
Antimicrobial Resistance ◽  
Resistance Genes ◽  
Broiler Chickens ◽  
Virulence Genes ◽  
Virulence Gene ◽  
Health Concern ◽  
Pathogenicity Test ◽  
E Coli ◽  
Antimicrobial Resistance Genes

In the current study, ten avian pathogenic E. coli (APEC) isolates of the most predominant APEC serogroups isolated from broiler chickens in Egypt were screened for their virulence and antimicrobial resistance genes pattern using PCR. Five selected virulence gene patterns were further investigated for their in-vivo pathogenicity test. Results showed a 100% prevalence of the β-lactams and tetracyclines resistance genes. However, aminoglycoside and quinolone resistance genes were not detected. Also, 80% of the tested isolates harbored mcr-1 gene, colistin resistance gene. In-vivo pathogenic strains consistently harbored the virulence gene pattern of fimH, fimA, papC, iutA, and tsh. Additionally, the tsh gene was consistently detected with lethal APEC isolates in day-old chicks. These results highlighted the high prevalence of antimicrobial and virulence genes in APEC that potentially represent a public health concern. In this study, the virulence genes fimH, fimA, papC, iutA, and tsh were the most common virulence gene patterns associated with pathogenicity in day-old chicks.

scholarly journals 2429. Whole-genome Sequencing of Healthcare-Onset C. difficile Infection (HO-CDI) Cases Shows Widespread Presence of Antimicrobial Resistance Genes

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S839-S840
Author(s):  
Jae Hyun Shin ◽  
Deiziane Viana da Silva Costa ◽  
Hardik Parikh ◽  
Katie E Barry ◽  
Amy J Mathers ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Resistance Genes ◽  
Susceptibility Testing ◽  
De Novo ◽  
Antimicrobial Treatment ◽  
Small Sample ◽  
Binary Toxin ◽  
Future Research ◽  
Toxin Gene ◽  
Antimicrobial Resistance Genes

Abstract Background Clostridioides difficile infection (CDI) is the most common pathogen to cause healthcare-associated infections. Unlike some other bacterial pathogens antimicrobial treatment is seldom based on culture with susceptibility testing with infrequent surveillance for antimicrobial resistance. We have evaluated healthcare-onset CDI (HO-CDI) for both transmission and antimicrobial resistance emergence. Methods We identified cases of HO-CDI diagnosed by PCR within a 3 month period (October 1/2018–December 31/2018) at University of Virginia Health System with overlapping stays in the same inpatient units with other HO-CDI. Chart review of all cases was performed. C. difficile was cultured from stool, then DNA was extracted and underwent sequencing on Illumina Miseq platform. Antimicrobial resistance genes were screened using NCBI’s AMRFinder tool from the de-novo assembled contigs using SPAdes. All the C. difficile isolates underwent antibiotic susceptibility testing. Results Eleven patients were identified with overlapping stays from 5 units. Mean age was 64 years and 63.6% were female. 36.3% of cases were severe CDI with one case of fulminant CDI. There was one recurrence within 90 days (9.1%). Patients were treated with PO vancomycin (72.7%) or IV metronidazole and PO vancomycin (27.3%), none were treated with metronidazole alone. None of the hospital strains were genetically related. There were two isolates with binary toxin gene (cdtB), one ribotype 027 (CD196) and one ribotype 078 (M120). Ninety-one percent of isolates had vanG-like gene cluster and vanZ1 originally identified in Enterococcus sp. erm(B), tet(M), and cfr(C) genes were also detected in several strains. All isolates were susceptible to vancomycin, metronidazole, and tigecycline. There was one strain with moxifloxacin resistance associated with the presence of erm(B) gene. None of the isolates were susceptible to clindamycin. Conclusion There were no widely circulating clones or direct transmissions found in this small sample of HO-CDI cases at our hospital. Like others have we demonstrate carriage of many vanG/Z genes without conferring phenotypic resistance to vancomycin. The origin and function of Van genes in C. difficile could be an area of future research. Disclosures All authors: No reported disclosures.

Antimicrobial Resistance at Two U.S. Cull Cow Processing Establishments

2020 ◽  
Vol 83 (12) ◽  
pp. 2216-2228
Author(s):  
JOHN W. SCHMIDT ◽  
AMIT VIKRAM ◽  
TERRANCE M. ARTHUR ◽  
KEITH E. BELK ◽  
PAUL S. MORLEY ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Dairy Cows ◽  
Beef Cows ◽  
Health Impact ◽  
The United States ◽  
Generation Cephalosporin ◽  
E Coli ◽  
Study Results ◽  
Antimicrobial Resistance Genes ◽  
Organic Dairy

ABSTRACT Culled beef cows (cows that have reached the end of their productive life span in cow-calf operations) and culled dairy cows represent approximately 18% of the cattle harvested in the United States annually, but data on antimicrobial resistance (AMR) in these cull cattle are extremely limited. To address this data gap, colon contents were obtained from 180 culled conventional beef cows, 179 culled conventional dairy cows, and 176 culled organic dairy cows (produced without using antimicrobials). Sponge samples were also collected from 181 conventional beef, 173 conventional dairy, and 180 organic dairy cow carcasses. These samples were obtained on 6 days (3 days each at two beef harvest and processing establishments). At one establishment, 30 samples of beef manufacturing trimmings from conventional cows and 30 trim samples from organic dairy cows were acquired. All 1,129 samples were cultured for Escherichia coli, tetracycline-resistant (TETr) E. coli, third-generation cephalosporin-resistant (3GCr) E. coli, Salmonella, and 3GCrSalmonella. Metagenomic DNA was isolated from 535 colon content samples, and quantitative PCR assays were performed to assess the abundances of the following 10 antimicrobial resistance genes: aac(6′)-Ie-aph(2″)-Ia, aadA1, blaCMY-2, blaCTX-M, blaKPC-2, erm(B), mecA, tet(A), tet(B), and tet(M). For colon contents, only TETrE. coli (P &lt; 0.01), 3GCrE. coli (P &lt; 0.01), and erm(B) (P = 0.03) levels were higher in conventional than in organic cows. Sampling day also significantly affected (P &lt; 0.01) these levels. Production system did not affect the levels of any measured AMR on carcasses or trim. The human health impact of the few significant AMR differences could not be determined due to the lack of standards for normal, background, safe, or basal values. Study results provide key heretofore unavailable data that may inform quantitative microbial risk assessments to address these gaps. HIGHLIGHTS

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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