| As an important food-borne opportunistic pathogenic bacterium,Staphylococcus aureus can cause serious infections of the bloodstream,skin and soft tissue in humans and animals.Bacterial resistance has been promoted with the rapid development of antimicrobial agents.S.aureus and the resistance characteristics in food animals could be transmitted to human via food chain,which may pose serious threats to human health and become a hot research of the world.At present,S.aureus have been detected in different parts of pork production chains.However,no systematic and in-depth research on the prevalence and characteristics of S.aureus isolated from pork production chains.The objective of the present study was to characterize and compare 128 porcine S.aureus isolates collected at swine farm,abattoir,and market pork production using antimicrobial susceptibility testing,multiple locus sequence typing,spa typing,and resistance gene screening.The main research results are as follows:(1)Epidemiological characteristics of S.aureus on swine farms.The prevalence of S.aureus and MRSA were 17.3% and 1.2%.Isolates were predominantly resistant to PEN,GEN,TET,CLI,CLA,SXT,CIP and MOX with the resistant rates were more than 90%.Multidrug resistance was observed in all the S.aureus isolates.Isolates were predominantly resistant to seven classes of antimicrobials(22/29)and the number of resistance patterns were eleven.The gene blaZ,ant(4′)-Ia,aadE,aacA-aphD,aac(6’)/aph(2”),tetL,lnuB,lsaE and dfrG were commonly found.The most frequently recovered ST and spa-type were ST9-t899.(2)Researches on the characteristics of S.aureus in abattoirs.Of the samples from the abattoir,35.8% and 5.2% were positive for S.aureus and MRSA.The resistant rate to PEN was 98.39% and 20~45% for GEN,TET,CLI,CLA and SXT.Eighteen resistance patterns were formed.Isolates displayed a high prevalence of gene blaZ,ant(4′)-Ia,aacA-aphD,catI,tetK,tetL and lsaE.ST188-t189,being the most prevalent ST and spa-type.(3)Epidemiological studies of S.aureus on market.The prevalence of S.aureus and MRSA were 23.1% and 6.3%.More than 50% of isolates from the farms were resistant to PEN,CHL,TET,CLI and CLA.Multidrug resistance was observed in 72.97%(27/37)of the S.aureus isolates.Multidrug resistance was 72.97%(27/37)and the number of resistance patterns were twenty-seven.The gene blaZ,ant(4′)-Ia,aacA-aphD,catI,tetK and lsaE were commonly found.The most frequently recovered ST and spa-type were ST7-t091.(4)Overall,abattoirs had the highest prevalence of S.aureus(35.8%)of the areas screened,followed by markets(23.1%)and farms(17.3%),and the prevalence of MRSA was 5.2%,6.3% and 1.2% respectively.All 128 isolates from pig farms,slaughter rooms,and retail stores were predominantly resistant to TET(63.28%),CLI(57.03%),CLA(57.03%),SXT(43.75%),GEN(40.63%),CIP(39.06%),MOX(33.59%),CHL(25.00%)other antibiotics(<25%).Those isolates were susceptible to quinupristin-dalfopristin,linezolid,and vancomycin,while the resistance rates were various to other antibiotics.Moreover,59.4%(76/128)of the isolates were MDR and 51 patterns of resistance for 9 categories of antimicrobials were found.For antibiotic resistance genes detection,blaZ was present in all isolates.Genotypic and phenotypic antibiotic resistance of S.aureus differed significantly among different antibiotics except penicillin.Isolates from farms,abattoir and markets were analyzed by MLST and spa typing,which were identified with ST9-t889,ST188-t189 and ST7-t091,respectively,being the most prevalent.A total of 20 STs and 15 spa-types were found and ST9-t889(30.5%)was the main sequence typing in different sources.In conclusion,this study showed pig slaughtering and processing play an important role in the acquisition and cross contamination of S.aureus along the food production chain.Meanwhile,pigs and pork could be important players in S.aureus dissemination.The study provided foundation for the risk assessment of S.aureus in the pork processing chain. |
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