Virulence gene detection and Spa typing of Staphylococcus aureus

Objective To study the distribution of virulence genes and the Spa types of Staphylococcus aureus isolated from patients, smears of material surface and medical workers' hands and samples from food poisoning cases in Nanshan district in Shenzhen from 2009 to 2015. Methods The mecA and femA genes of S.aureus were detected by multiplex polymerase chain reaction (PCR). Twenty four kinds of virulence genes and protein A gene of S.aureus were detected by PCR, the products of PCR were sequenced and the results were aligned with those in Spa database. Results Among 87 S.aureus strains,48(55.2%) were methicillin-resistant S. aureus (MRSA). Twenty one virulence genes were detected, the virulence genes with detection rate 60% included LUKDE(65.5%), SHE(67.8%), mpHL G2(85.1%),HLD(93.1%), HLA(100.0%). Up to 94.3% of the strains carried more than 5 virulence genes. The positive rates of 11 of kinds virulence genes(SEB,mpSEC, mpSEJ, mpSEO,TST, HLB, HLD, mpHL G1, mpHL G2, mpETB, PVL) were different. MpETB and PVL genes were detected only in patient samples.The positive rate of enterotoxins in food poisoning samples was higher.The positive rates of 3 kinds of virulence genes(mpETA,PVL,mpHL G2) were significantly different between MRSA and methicillin-sensitive S.aureus (MSSA). The positive rates of mpETA and PVL were higher (P=0.033, P=0.030), but the positive rate of mpHL G2 was lower in MRSA strains (P=0.021). Among the 87 strains,24 Spa types were identified. t437 and t030 were the top two Spa types of S.aureus strains from patients, accounting for 36.7% and 30.0% respectively, t091 was the predominant Spa type of S.aureus from smears of material surfaces and medical workers' hands, accounting for 50.0% and t127 and t091 were the top two Spa types of S.aureus from food poisoning samples, accounting for 36.8% and 21.1% respectively. Conclusion The positive rates of virulence genes in the S.aureus strains from 3 kinds of samples were significantly different, but the positive rates of virulence genes in MRSA and MSSA had no significant difference. There were predominant Spa types in the S.aureus strains from 3 kinds of samples.