Antibiotic And Disinfectant Resistance Of Escherichia Coli Isolated From Animal-Derived Foods

Escherichia coli as an important indicator bacteria of the National Antimicrobial Resistance Monitoring System (NARMS) can spread thoughout the food chain and infect humans as well as animals causing diarrhea. E. coli infected with stronger serotypes can be fatal. Many classes of antimicrobial agents that are used in humans also are used in food animals for growth promotion, disease prevention, and therapy. Antibiotics are an important method in the prevention and treatment of E. coli infections and other pathogens, due to the widespread and irrational use of antibiotics, the use of antimicrobial agents in food animals increases the likelihood that E. coli have food animal reservoirs, will develop cross-resistance to drugs approved for use in human medicine, the antibiotic resistance to foodborne E. coli is rising. In order to further reduce the harm of antibiotic resistam bacteria and incidence of infection, environmental disinfection control has become one of the main measures in controlling the spread of pathogens. Currently, Quaternary Ammonium Compounds (QACs) are being widely used as disinfectants in farming and food processing environments. Many scholars are concerned about the problem of whether or not the increased use of disinfectants can cause bacterial resistance to disinfectants. Antibiotic resistance has also been reported along with Quaternary Ammonium Compounds disinfectant-resistance. At present, few reports exist regarding E. coli from animal food resistance to disinfectants and the co-resistance of disinfectants and antibiotics.In this study, the samples of meats were collected from farmers’markets or supermarkets in Sichuan, Province. E. coli were isolated by conventional tests and identified by 16S rDNA. Antimicrobial susceptibility of these isolates were determined by standard disk diffusion methods according to CLSI guidelines. MIC of QACs of these isolates were determined by agar dilution methods. Disinfectant-resistant genes and Class 1 were detected by PCR. Isolates which include Plasmid-borne Disinfectant-resistant genes typing by PFGE. Some isolates were selected for conjugation experiments.1. The detection of antibiotic rates of E. coli from meats203 pork,66 beef and 59 chicken samples were collected in Sichuan Provinces between 2009 and 2013. E. coli were isolated using selective medium and confirmed by 16S rDNA.255 E. coli were obtained. E. coli had the highest occurrence in chicken (n=50, 84.75%), followed by pork (n=161,79.31%) and beef (n=44,66.67%). The susceptibility of 11 antibiotics was performed according to the standard disk diffusion method recommended by the Clinical and Laboratory Standards Institute (CLSI). Antimicrobial susceptibility of these isolates to 11 different agents indicated the following:the resistance of 218 isolates (85.49%) to 11 different agents were different. The E. coli isolates showed the highest resistance to sulfamethoxazole (61.57%), followed by tetracylin (61.18%), and ampicillin (48.24%).126 isolates (49.41%) exhibited multiple resistance to 3-9 antimicrobial agents. The rate of resistant strains to 3 agents was highest, followed by 5 agents. Dominant resistant patterns among these isolates were S3 (n=21), S3-TET (n=18), TET (n=16), and AMP-S3-TET (n=13). The conjugation experiment indicated that qacF, qacE△1, and sugE(p) could transfer among the bacteria with same genera.2. QACs disinfectant resistance of E. coli from animal-derived foodMICs of QACs were determined by the agar dilution method. The prevalence of 10 qac resistant genes and Class 1 were determined by PCR. Some isolates were choosen for conjugation experiments to prove whether or not the plasmid-borne genes transferable. We analyzed the connection between antibiotics resistance and Class 1.The ranges of MICs of 255 E. coli were CPC 8-512 mg/L, CTAB 16-512 mg/L, BC 16-1024 mg/L and DDAC 4-1024 mg/L. The detection frequency of the ydgE gene was highest (87%; 221/255), followed by mdfA (85%; 218/255), sugE(c) (83%; 212/255), ydgF (80%; 203/255), emrE (78%; 200/255), qacE△1 (20%; 50/255), qacF (18%; 46/255), and sugE (p) (7%; 7/255). qacE and qacG were not detected in any of the isolates. The results indicated that the detection rate of Class 1 was low, with 66 isolates exhibiting Class 1. This prevalence of Class 1 has been associated with antibiotic resistant. Conjunction experiments indicated that plasmid-borne qac genes can transfer to recipient strain and rising QACs MIC of E. coli. The detection rate of qacF gene in antibiotic resistant bacteria was higher than the antibiotic sensitive strains (p<0.05), qacE△1 gene of E. coli from pork was associated with antibiotic resistance significantly.3. PFGE typing of plasmid-borne QACs genes E. coli96 plasmid-borne genes E. coli were typed by PFGE. Results showed these isolates can be divided into 13 PFGE types and 73 subtypes. Some E. coli isolated from the same place have the similar PFGE types, strains of the similar antibiotic susceptibility pattern were correlated with the same PFGE groups. Due to my Research we found that some strains showed disinfectant-resistant genes were correlated with PFGE Type. (ie, Type A and Type B are Positive for Genes emrE-mdfA-sugE(c)-ydgE-ydgF-qacF and Type C for mdfA-sugE(c)-ydgE-ydgF-qacE△1).Our findings indicated that the contamination of E. coli in retail meats in Sichuan is serious. The resistance frequency and multi-drug resistance was lower than in other reports. The frequency of QACs resistance genes and the MIC of QACs were high. Besides, we found that resistant strains were associated with locations. Therefore, we should strengthen monitoring of the E. coli contamination and drug resistance in retail meat, and focus on the prevention and control of the spread of drug resistance of retail meat contaminated with E. coli.