Prevalence And Characterization Of Chickenborne Salmonella Serovars In Eight Provinces And Cities Of China

Salmonella is one of the most important foodborne pathogens worldwide. Foods ofanimal origin are frequently contaminated with the pathogen and can serve as vehicles intransmitting salmonellosis in humans. A survey on Salmonella in chicken from part of Chinawas conducted to determine the prevalence, and phenotypic and genotypic characteristicsincluding serotype, antimicrobial susceptibility, genomic subtype, plasmid subtype andantimicrobial resistance genes. Major findings and conclusions were summarized in thefollowing:(1)Salmonella contamination in chicken from supermarket and freemarket in Shaanxi,Sichuan,Guangxi,Guangdong,Fujian,Henan,Beijing and Shanghai provinces(cities), thecontamination rates ranged from50%,38.9%,65.3%,64.6%,42.4%,48.6%,64.6%to43.8%respectively. The most polluted province is Guangxi(65.3%), and the opposite province isSichuan provinces(38.9%).(2) The serotypes and genetypes of chickenborne Salmonella were diverse. Among399Salmonella isolates recovered in the study,44serotypes were identified as S.Enteritidis(20.2%) being most common, followed by S. Typhimurium (17.3%), S. Indiana (15.6%) and S.Thompson (10.8%). Several rare serotypes, such as S. Rissen, S. Agona, S. Braenderup, S.Litchfield, S. Pakistan and S. Bsilla, were identified as well.271of pattens were generatedwhen the chromosome DNA of Salmonella was digested with restriction endonuclease Xba land analyzed using pluse-field gel electrophoresis (PFGE). Serotyping and PFGE results werein agreement although PFGE was much discriminatory than serotyping.(3)The Salmonella isolates also exhibited resistance to antimicrobials. Multidrugresistance (MDR) was common. Of the399isolates,69.8%was resistance to tetracycline,69.3%was resistant totrimethoprim/sulfamethoxazole,62.0%to nalidixic acid,53.0%toampicillin,45.3%to amoxicillin/clavulanic acid,37.3%to chloramphenicol and36.3%tokanamycin.150(37.6%) isolates strains were resistant to at least1-3antimicrobials,91(22.8%) were resistant to at least4-6antimicrobials, and61(15.3%) were resistant to at least 7-9antimicrobials,69(17.39%) to10or more. The common serotypes of MDR Salmonellaincluded Salmonella Edinburgh, S. Indian, S. Rissen, S. Typhimurium and S. Enteritidis.(4)Among the390Salmonellae isolates,63.59%(248strains) were resistant toNalidixic Acid, followed by resistant to ciprofloxacin (21.28%), Levofloxacin (16.67%), andGatifloxacin (14.62%). Among248nalidixic acid resistant Salmonella, antimicrobial resistantgenes carried by plasmid were detected as aac(6')-Ib-cr (20.16%),qnrA (10.89%),qnrB(10.08%) and qnrS (1.61%), respectively. One hundred ninty-nine point mutations weredetected in gyrA and parC of83fluoroquinolone-resistant Salmonella isolates. The mostcommon mutations in gyrA gene were Ser83Phe and Asp87Gly double mutation, followed bySer83Phe and Asp87Asn double mutation, Ser83Tyr,Ser83Phe, Asp87Gly, respectively.Sixty five point mutations were detected in parC was Ser80Arg.(5)Among242Ampicillin resistant Salmonella, plasmid was found in160strains(66.1%). The numbers of plasmids ranged from1to6,Most of strain carried1-3plasmids．The molecular weight of plasmid was from1.1×103bp to50.0×103bp.It has77kinds of plasmid subtype. the size of plasmid DNA carried in strains were mainly8.0kb. andthere is no contact between antimicrobial susceptibility, serotypes and plasmid subtype.