| Considering Staphylococcus aureus as one of the most important foodborne pathogen in the pig-breeding industry, the drug resistance and virulence of Staphylococcus aureus could be spread from animals to human through contact, which poses a direct threat to human health. In this study, we collected 507 s amples from livestock, slaughtering room and markets, according national standard GB 4789.10-2010 to isolate and identify S.aureus from samples, gene typing was conducted by multilocus sequence typing(MLST) and spa method, drug susceptibility testing was performed by disk diffusion method and E-test, using PCR technology to detect resistance gene and virulence gene of 136 S.aureus. The content and results are as follows:Firstly, According national standard method to isolate and identify S.aureus, we got 136 isolates totally from 507 samples. The prevalence of S.aureus in the pork farms(n= 168), slaughtering room(n=176), stock(n=53) and market(n=110) samples was 17.26%, 39.63%, 16.98% and 30%, respectively.136 foodborne S.aureus were tested for antibiotic susceptibility, which was performed by disk diffusion method and E-test as CLSI 2012 recommend. Resistant level to antimicrobials for all isolates included: the highest adjusted prevalence of resistance was to PEN(92.64%, 126/136), followed by TET(56.61%, 77/136), CLI(50.00%, 68/136), CLR(49.26%, 67/136), SXT(41.91%, 57/136), CIP(39.71%, 54/136), GEN(29.41%, 40/136), DHL(24.26%, 33/136), which among 24.26% and 56.61%. Additionally, the proportion of multidrug-resistance isolates was 56.62%(77/136). The main resistance profile of all the isolates were different according sources of samples.PCR were performed for verifying resistance genes and virulence genes. Among the 136 isolates, the high prevalence was tet K(90.44%, 123/136), of which 6 isolates carry both tet M and tet K. The detection of raw meat from market was 24.24% and erm A/B/C were 16.42%, of which the prevalence of erm B reached 11.76%. Virulence genes vary from different sources of strain and some of the virulence gene reached high rate. Among all the detected virulence genes, hla distribution range from 14%~100% and total positive percentage was 48.5%. Among the 136 i solates, 21 i solates(15.44%) were positive for mec A gene, none of the isolates carry mec C gene and pvl.In order to identify the correlation and characteristics of S.aureus isolates, MLST and spa typing was performed for 18 MRSA isolates. In total, seven types were detected: ST9, ST1, ST398, ST188, ST239, ST1516 and ST7. ST9 was dominating type among the MRSA in China. Which corresponding to spa, we got 7 types of spa: t899(27.78%, 5/18), t189(16.67%, 3/18), t037(16.67%, 3/18), t1852(16.67%, 3/18), t091(11.11%, 2/18), t1775(5.56%, 1/18), t034(5.56%, 1/18).In summary, the food chain of raw meat were severely contaminated with S.aureus, and characterize of bacteria was notable and has serious antimicrobial resistance phenomenon, which lied foundation for the antimicrobial resistance and molecular epidemiology of S.aureus in the pork processing chain. |
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