| Overuse of antibiotics lead to the emergence of drug resistant bacteria and flooding, thedrug resistance of bacteria and their drug resistance genes can be spread from animals to humanthrough food chain, which pose a direct threat to human health. In this study, we collected110raw pork from six supermarkets and three teminal markets in Guangzhou, according nationalstandard GB4789.10—2010to isolate and identify S.aureus from samples, gene typing wasconducted by multilocus sequence typing (MLST) method, drug susceptibility testing wasperformed by disk diffusion method (K-B method), using PCR technology to detect class oneintegron of34S.aureus, and study on class one integrase (IntI1) mediated resistance genecassette in a horizontal transfer between different bacteria. The content and results are asfollows:Firstly，according to random sampling method collected110raw pork samples，of which50copies were fresh meat,29copies were ribs, and31copies were organs. According nationalstandard method to isolate and identify S.aureus, total of34samples detected S.aureus, eachpositive samples kept one isolate, got34isolates of S.aureus totally. Of which, the detectionrate of fresh meat were32%, ribs had the highest detection rate of34.5%, and the organs were25.8%, the detection rates were no significant differences among different samples. Thedetection rate of samples which from suerpmarkets were32%(24/75), and from teminalmarkets were28.6%(10/35).34foodborne S.aureus were tested for antibiotic-susceptibility, which was performed bydisk diffusion method as CLSI2012recommend. The drug resistance rate in descending orderwere: PEN (100%), TET (88.2%), TMP (76.5%), EM (64.7%), CLI (61.8%), RIF (44.1%),FOX (38.3%), MNO (35.3%), CHL (17.6), GEN (17.6), NOR (14.7), and FD (8.8%). Thedetection rate of MRSA were38.3%(13/34), PCR were performed for verifying its mecA gene,contrast with the result of drug sensitivity testing, coincidence rate was76.9%(10/13). In thisstudy, we got26different drug-resistant spectrum, and5.9%(2/34) displayed resistance to twokinds of antimicrobials,5.9%(2/34) displayed resistance to three kinds of antimicrobials,11.8%(4/34) displayed resistance to four kinds of antimicrobials,23.5%(8/34) resistance to five kindsof antimicrobials, and52.9%(18/34) resistance to more or more than six kinds of antimicrobials, and more than66.7%multi-drug resistant strains were resistnt for β-lactams, macrolides andtetracyclines.In order to identify the correlation and characteristics of S.aureus isolates, MLST wasconducted for the gene typing. A total of7STs were found among34strains, respectively forST6(1/34), ST7(16/34), ST9(9/34), ST59(1/34), ST239(4/34), ST2259(2/34), and obtain anew ST, which allelic spectrum was5-4-1-4-4-6-53. ST7were the major sequence typing inthis study, accounting for47.1%; followed by ST9,26.5%; MRSA were found to have two STs,ST9(6/10) and ST239(4/10) respectively.34strains of S.aureus were conducted for the amplification of the IntI1gene, showed thatthe carrier rate of IntI1gene were14.7%(5/34), then PCR detection of variable region for fiveClass one integrase positive strains, and the results showed two strains had gene cassette,sequencing, got frA17-aadA5and EstX gene cassette respectively. Extraction of plasmid fromthe strain which contained frA17-aadA5gene cassette，and study on IntI1mediated resistancegene cassette in a horizontal transfer between different bacteria: transformation and naturalmetastasis, reults show that class one integron can mediate resistance gene cassette in ahorizontal transfer.In summary, raw pork were severely contaminated with S. aureus, and the strains ofS.aureus have serious antimicrobial resistance phenomenon, ST7were the main sequencetpying, Class one integrons existed in foodborne S. aureus, the phenotype of drug resistantstrains was correlated with Class one integron that it carried. |
PDF Full Text Request