Antimicrobial resistance and molecular typing of methicillin-resistant Staphylococcus aureus from pigs in Henan Province

The objective of the present study was to determine the prevalence and phenotypic profiles of methicillin-resistant Staphylococcus aureus(MRSA)from pigs in Henan provinces.Nasal samples(n=1 107)were collected from pigs on 3farms and 1slaughtering house.S.aureus and MRSA were isolated by using the selective medium and identified using multiplex PCR(16SrRNA and nuc for SA;16SrRNA,nuc and mecAfor MRSA).Antimicrobial susceptibility testing was performed using disk diffusion,and the colony relatedness of these MRSA strains were analyzed by the pulsed-field gel electrophoresis(PFGE),multilocus sequence typing(MLST)and staphylococcal protein A(spa)typing.A total of 358 S.aureusisolates,including 119 MRSA isolates,were identified from 1 107 pig nasal samples.66.39% of the MRSA isolates were simultaneously resistant to 15 antimicrobials,and the resistance rates of quinupristin/dalfoopristin and rifampin were 1.7% and 0.8%,respectively.However,no isolates were resistant to vancomycin and linezolid.The results of PFGE showed diverse genetic profiles of these MRSA isolates.The major ST type of these MRSA isolates from pigs was ST9,and the major spatype was t899.The isolating rate of MRSA from pigs in Henan Province was higher than that from other provinces in China and the MRSA isolates of diverse profiles were seriously resistant to most antimicrobial agents.The majority of MRSA isolates was ST9-t899 type.The findings of this study provided base-line data for monitoring the dissemination of MRSA and conducting effective control measures in provinces of swine production in China.