Study On Resistance Genes And PFGE Typing Of Escherichia Coli And Salmonella During The Layer Breeding Cycle

Escherichia coli and Salmonella are important bacterial pathogens to breeding industry,and bring enormous losses, colibacillosis in chicken mainly appear as pericarditis,perihepatitis, salpingitis and yolk peritonitis, Chicken infect with Salmonella mainly appear asenteritis and septicemiamain, and Salmonella can cause human infections throughcontaminated eggs, therefore, to carry out the chicken Escherichia coli and Salmonellamonitoring study has important economic and public health significance. In this study, alarge-scale farms in Tongchuan of its layer flocks as the research object, continuous trackingof the entire breeding cycle of chicks, young chicken and laying period,120Escherichia coliand42Salmonella separated and saved during the breeding cycle, analysis of the drugresistance, resistance genes and PFGE gene types, in order to explore the variation ofresistance and resistance genes of E.coli and Salmonella strains during layer breeding cycle,for screening security-sensitive antibiotics clinically, and provide references to establishbacterial species library and database of bacterial resistance epidemiological survey.1. With reference to CLSI (clinical and laboratory standards institute), antimicrobialsusceptibility of120chicken E.coli isolates and42chicken Salmonella isolates against18antimicrobials were determined by the Kirby-Bauer disk method. Resistance showed noobvious changes among chicks, youth period and laying period. The antimicrobial resistanceof E.coli to ampicillin, streptomycin, tetracycline and nalidixic acid are more than90%; Drugresistance to amoxicillin, gentamicin increased first and then decreased, and resistance ratereach the highest during the peak of egg production. Resistance of E.coli isolates have slowupward trend to co-trimoxazole, tobramycin and neomycin, and a downward trend toceftazidime and doxycycline. Resistance of chicken Salmonella isolates to ampicillin,tetracycline, nalidixic acid, norfloxacin and ofloxacin are more than60%; the spectinomycinand ofloxacin resistance in the breeding cycle present an upward trend, and a downward trendof doxycycline resistance; All the isolates were resistant to at least3kinds of antimicrobials,multi-drug resistant rate up to100%.2. Resistance genes were detected among120chicken E.coli isolates and42chicken Salmonella isolates by PCR. There were8resistance genes that were been detected in thechicken E.coli isolates, the detection of resistance gene tetA, tetB, blaTEM, blaCTX-M,aac(3)-II and sul-I is significantly associated with their antimicrobial resistance (P<0.05);There were6resistance genes detected in the chicken Salmonella isolates, the detection ofresistance gene tetA, blaCMY-2, blaTEM-1and sul-II is significantly associated with theirantimicrobial resistance (P<0.05).3. Gel pulse field gel electrophoresis were used for PFGE typing of120chicken E.coli and42chicken Salmonella isolates, and analysis of homology between strains. Cluster analysisshowed that PFGE banding patterns of chicken E.coli isolates is complex, also showed acomplex genotype of chicken E.coli in this farm, but strains homology of75%to100%, thismay be inferred that one or a few species of similar strains vertically or horizontally due topropagation; Chicken Salmonella isolates can be divided into seven PFGE banding patterns,and type4was its advantage type, the first six banding pattern (41strains) homology betweenstrains were more than80%, indicating that the prevalence of chicken Salmonella inTongchuan chicken farm may be caused by one or a few strains initially; PFGE typing of thesame serotypes is not necessarily the same, PFGE typing of different serotypes strains may bethe same; Resistance spectrum were not necessarily the same among isolates with highly eventhe same homology.