Distribution Of Virulence Genes And Molecular Typing Of Staphylococcus Aureus Strains From Different Sources

Staphylococcus aureus is an important zoonotic pathogen that is associated with a series of disease for human and animals. With the increase of virulence and drug resistance, especially the emergence of MRSA, it’s a great challenge to the prevention and control of Staphylococcus aureus. It is extremely important to analyze the evolutionary relationships for tracing and transmission of S.aureus in different resources.1. Distribution of virulence genes of Staphylococcus aureus strains from different sourcesGenes encoding HL α, HL β, FnbpA, FnbpB, ETA, ETB, TSST-1and PVL were detected in a total of4985. aureus isolates from different sources. Overall,82.33%(10/498)of S. aureus isolates were found to be positive for at least one toxin genes,46.59%(233/498) of S. aureus carries two and more toxin gene. Moreover, the result showed that except ETA and TSST-1, other six toxin genes can be detected from different source samples.Based on the different virulence genes harbored,498S. aureus isolates were divided in30toxin gene type. The HL a gene was found most frequently (70.88.%), followed by FnbpA (32.53%), HLβ(31.33%),ETA (21.8%), PVL (9.25%), FnbpB(6.11%),TSST-1(5.44%) and ETB(0.87%). The HL α, HL α-FnbpA and HL α-HL β-FnbpA was the most common virulence genotypes in the strains which from human,but the isolates from environmental and animal sources,The main virulence genotypes were HL α,HL α-HL β and HL α-HL β-FnbpA 2molecular typing of Staphylococcus aureus strains from different sourcesAmong the242S. aureus isolates,65were identified to MRSA (26.9%). About27.3%(30/110) of strains from human tissue samples was MRSA; about28.6%(16/63) of strains from environment were found to be CA-MRSA; and24.6%(17/69) of strains from animals were found to be CA-MRSA, including25.81%(12/25) of swine derived strains and50%(5/10) of bovine derived strains.The65MRSA isolates were analyzed by SCCmec typing, and4SCCmec types were detected. The results showed that7.7%(5/65),26%(13/65),4.6%(3/65) and46.2%(30/65) of the strains belongs to SCCmec types Ⅱ,Ⅲ, Ⅳb and Ⅴelement, respectively. In addition,21.5%(14/65) MRSA isolates could not be classified to any type. Among those,30MRSA isolates were collected from patients,12were defined as typeⅢ,7were defined as type Ⅴ,5were defined as type Ⅱ, and6were untypable; all the strains derived from environment and cows were classified to SCCmec type V; while the strains of SCCmec type IVb (n=3) and type Ⅲ (n=1) belonging to CA-MRSA were from pigs.52ST types were identified from250isolates which were selected to MLST typing. Four new alleles were defined from the gmk and pta locus, and four new STs (ST2630, ST2631, ST2710and ST2711) were identified and added to the S. aureus MLST database. In this research, The ST630was identified as the most common ST types, followed by ST9, ST239and ST9. ST630, ST239, ST5, ST9, ST5and ST398were found in MRSA and MSSA isolates, which showed that the MSRA isolates were probably from MSSA by acquiring the SCCmec elements. The52STs were assigned into five eBURST analyses distributed the sequenced isolates into several Cs. ST630, ST2205, ST2711and ST8belonged to CC8, ST9, ST15, ST25while ST2630belonged to CC15.