Characterization Of Escherichia Coli From Retail Meats And Ready To Eat Food In Some Districts Of Shaanxi Province

Nowadays, due to the abuse of antibiotics, antibiotic resistance of bacteria are considerably serious. Moreover, the dissemination of multiple drμg resistant bacteria could place great challenge on clinical practice and threaten to human health, and result in hμge financial loss. Furthermore, bacteria could infect human body via food chain, as a result, it is of great importance to survey and monitor bacteria antibiotic resistance. Escherichia coli is normal intestinal flora in warm blood animals, so it is believed that Escherichia coli is an indicator of both food sanitary and antibiotic resistance condition of the bacteria in food. In this study, Escherichia coli were isolated from samples purchased in Xi'an and Yangling in Shannxi province, then their antimicrobial minimum inhibitory concentrations (MICs) were determined as well as their integron and pathogenic Escherichia coli. In the end the horizontal transfer of antibiotic resistance between Escherichia coli were studied. The results are as follow:1. A total of 748 Escherichia coli isolates recovered from 357 samples of retail meats and ready-to-eat food purchased at different supermarkets and free markets in Shaanxi Province were examined in this study. 89% of the samples were contaminated by Escherichia coli . Their antimicrobial minimum inhibitory concentrations (MICs) were determined, the result showed that the isolates were most resistant to streptomycin at 88.2%, followed by Tetracycline at 84.4%, Trimethoprim-sulfamethoxazole at 64.4%, Nalidixic acid at 62.6%, Ampicillin at 56.0%, Ciprofloxacin at 39.2%, Chloramphenicol at 37.6% , Kanamycin at 34.9%, Gentamicin at 34.2%, Amoxicillin-clavulanic acid at 28.9%, Gatifloxacin at 26.9%. the isolates were most susceptible to Amikacin at 8.3%, as to Cefoxitin at 11.5%, Ceftriaxone at 13.8% and Cefoperazone 19.5%. Multiple resistant Escherichia coli were found in each sample origins. The condition of multiple resistance was most severe among Escherichia coli isolated from chicken as 92.4% of them were multiple resistant. Meanwhile isolates resistant to all antibiotics used in this study were isolated from chicken. The prevalence in pork, mutton, beef and read-to-eat food were 75.3%, 67.8%, 52.2% and 46.4% respectively.2. An Multiple PCR were established to detect the pathogenic Escherichia coli . 2 Enteroaggregative E.coli; EAEC (aggR positive);4 Enteropathogenic E.coli EPEC(eaeA positive);1 Shiga toxin producing Eschericia coli(stx1 and stx2 positive)were detected;1 pathogenic Escherichia coli 1(st and stx2 positive) could be classified;no Enteroinvasive E.coli(EIEC)were detected.3. 140 Escherichia coli isolates were chose based on the antibiotic resistance profiles to determine the presence of class 1 integrons. 23.6% of the tested isolates were integron positive. Two kind of integron were found, one is 1.5kb which contained dfrA1-aadA2 gene whereas the other is 1kb which contained aadA22 gene.4. Factors involved in horizontal transfer of antibiotic resistance between Escherichia coli isolates and conjμgation frequency were studied in this experiment. E. coli strains E11-83 (resistant to streptomycin) and E6-203 (resistant to nalidixic) were used as donor and recipient strains respectively to study the influences of donor/receptor ratio, culture time, temperature, culture medium, and antibiotic factors on conjugation frequency. The result shows that the highest conjugation frequency of 2.4×10-4 was observed at donor/receptor ratio of 1:8; Membrane culture method under aerobic condition was most effective, and had a conjugation frequency of 2.5×10-4; The conjugation frequency of culture method added with amoxicillin or not were 2.9×10-4 and 2.4×10-4 respectively. The highest conjugation ratio 3.5×10-4 was observed after culture for 16 hours. At 27℃, conjugation ratio is 3.1×10-4.In conclusion, our findings have shown that the antimicrobial resistance condition of Escherichia coli in food in Shaanxi province was common. And pathogenic Escherichia coli were detected; most of the isolates containing integron were multiple antibiotic resistant; antibiotic resistance could be transferred between Escherichia coli. This study provides useful and scientific data in directing clinical medicine practice and controlling the dissemination of antibiotic resistance among bacteria and food borne pathogens.