| Staphylococcus aureus is one of important human pathogens, which can cause avariety of diseases, it can lead to local suppurative infection, pneumonia, pseudomembranous enteritis, pericarditis and also cause sepsis, bacteremia, sepsis andsystemic infection, even threat the human lives. Methicillin-resistant Staphylococcusaureus (MRSA) emerged soon after the introduction of methicillin for the treatment of S.aureus infection. As the vast use of antibacterial drugs in clinical in recent years, therewast he severe antimicrobial resistance for MRSA, the difficulty of treatment and thehigh mortality rate. MRSA has become a global public health problem.In recent years, with the increase gradually in the farming scale and intensive, andextensive using of antimicrobials, it is a big change for epidemiology of the MRSA,Livestock-associated MRSA(LA-MRSA) has appeared which cause human seriousinfection, except hospital-associated MRSA(HA-MRSA) and community-associatedMRSA(CA-MRSA). And there were many studies and reports signs of MRSAtransmission between human and swine, it can threat to human health and have adverseimpact on treatment of bacterial diseases.From August2011to June2012, a total of348swine nasal swabs samples werecollected from eight large-scale swine farms and one pig slaughterhouse in Zhejiang,Jiangsu, Shanghai. A total of120sputum and throat swabs samples of human originwere collected from the patients in one hospital in Shanghai. S. aureus and MRSA wereisolated and identified by using75g/L sodium chloride broth, CHROMagar, duplexPCR(nuc and mecA) and resistance phenotype. We obtained174swine S. aureusisolates, in which89MRSA strains were identified and positive rate was25.6%(89/348).We obtained52human S. aureus isolates, in which15MRSA strains were identifiedand positive rate was12.5%(15/120), Minimum inhibitory concentrations(MICs) ofmultiple antibiotics were measured by broth dilution method. We examine theantimicrobial susceptibility of89swine MRSA strains on14antimicrobials in9classes.the antimicrobial susceptibility of15human MRSA strains on11antimicrobials in8classes. All of the MRSA isolates were susceptible to Linezolid, Vancomycin, the rest ofshowed different degrees of resistance to the other antimicrobial agents. Interestingly,all the MRSA isolates were high level resistance to pleuromutilin antibiotics(Tiamulin, Valnemulin and Retapamulin). These results also suggested that we should prevent thepotential transtion of resistant strains or resistant genes from animal to human, thistransition can be through the food chains or the enviroment.The MRSA isolates were characterized by staphylococcal chromosomalcassette(SCC) mec typing, multilocus sequence typing(MLST) and spa typing. AllMRSA isolates of swine origin were determined to be ST9-SCCmecIVb, andcharacterized as spa type t899(n=80) and t2922(n=9).14of the15human MRSAisolates were determined to be ST5-SCCmecII-t002. Another one was characterized asST88(MLST)-t10775(a novel spa type), however, the SCCmec type of this isolate couldnot determined. The results showed that swine MRSA were ST9-t899-SCCmecIVb, andhuman MRSA were ST5-t002-SCCmecII in Shanghai and surrounding areas. There isno signs of MRSA transmission between human and pigs in this study.Besides, in this study some MRSA isolated which are form swine and human arechosen to investigate the impact that the mutations of MRSA target genes have onresistance to fluoroquinolones. The results showed in grlA and gyrA target genes, themost of human MRSA were double point mutations, characterized on5kinds offluoroquinolone drugs of resistance value is very high, and swine MRSA were a pointmutation, characterized on5kinds of quinolones resistance value is very low. But grlBand gyrB target genes mutation is very low, there was only one strain of MRSA in thegrlB mutations, and the double point mutations (Glu561His Gly571Val), also only onestrain of MRSA in gyrB mutations, for the single mutation (Ala496THr). |
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