Isolation, Identification And Drug Resistance Analysis Of Salmonella Typhimurium In Broiler Industry Chain

Salmonella enteritidis is one of the most common reasons that leading food-borne pathogens. It is the main bacteria that result food-borne illness, in China. Due to the abuse of drugs in farm for a long time, drug-resistant Salmonella became more popular and serious. Researches had showed that salmonella which resistance to antibiotics had been in the steady growth, the resistance may be transferred to human bodies through the food chain. This situation made clinical antibiotic treatment become more difficult. This study was conducted to determine the prevalence of Salmonella, to evaluate antimicrobial resistance (AMR) and to analyze by pulsed field gel electrophoresis (PFGE) of Salmonella isolated along a broiler production chain from farm to retail. It is one of the guidance of drugs using in husbandry, and also be meaningful for public health.Samples were collected in Shandong, from April to September of 2013. It was 11 stages for collecting samples from farm level, slaughterhouse to market link. The methods for isolation and identification of Salmonella, applied by GB 4789.4-2010 and PCR.A total of445 (16.10%) Salmonella isolates were isolated from 2466 samples of the broiler production chain. The prevalence of Salmonella in farming link was1.33% in breeding bird, 31.63% in sick chicken,8.00% in health-chicken,13.00% in fattening chicken,9.75% in broiler ceca; The prevalence of Salmonella in slaughterhouse was 13.50% in broiler carcasses,14.49% in broiler carcasses after drip washing,25.54% in pre-cool liquid,26.26% in cool broiler carcasses,38.33% in broiler meat. The prevalence of Salmonella in market was 22.59% in retail broiler meat. The study showed that the prevalence of Salmonella-contaminated food products from slaughterhouse and market link was more serious than that from farm.Antimicrobial susceptibility testing of all isolates to 12 antimicrobials were performed, according to Kirby-Bauer test from the Clinical and Laboratory Standards Institute. The result show that high resistance rates were observed against to Nalidixic acid (NAD 93.48%), Ampicillin (AMP 76.85%). Overall 11.69%(52/445) of isolates were insensitive to tested antimicrobials including, cefazolin (CFZ 31.91%), doxycycline (DOX 29.21%), gentamicin (GEN 19.78%), trimethoprimsulfamethoxazole (SXT 15.06%) and Amoxicillin clavulanic acid (AMC11.69%).However, the percentages of resistance to the other antimicrobials Ceftazidime (CAZ), Chloramphenicol (CHL), Ciprofloxacin (CIP), Meropenem (MEM), polymyxinB (PB) is only 0.00%～10.00%. Of 445 Salmonella isolates 432 isolates (82.67%) were resistant to one or more antimicrobials, and 343 Salmonella isolates (77.08%) were resistant to more than one antimicrobial.In order to track the origins of Salmonella along a broiler chicken production chain, Salmonella enteritidis isolations from different sources and antimicrobial resistance patterns were analyzed by pulsed field gel electrophoresis (PFGE), according to the United States the CDC criteria for PFGE typing. The results showed that the PFGE of the strains of salmonella the similarity was from 36.59% to 100%, exhibited 32 PFGE patterns affiliated tol4 clusters. Furthermore, the major subtype X1 (20/48), covering strains from 6 sample collection sources, indicates the horizontal transmission via broiler production chain.