Distribution Of Enterotoxin Genes And SCCmec, Spa, MLST Typing Of Staphylococcus Aureus Strains From Different Sources

This study collected a total of 496 strains of Staphylococcus aureus in local from sample sources that included humans, tools, animals and food. Eighteen pairs of primers for enterotoxin genes(sea to see, seg to sei, and ser) and enterotoxin-like genes(selj to selq, and selu) from multiple studies were adopted. We designed a multiplex PCR assay for the 18 enterotoxin genes. Using the multiplex PCR assay, we detected the distribution of se and sel genes in 496 strains. Among these strains,34.27% carried classical types of SE genes (sea-see),27.02% carried novel types of SE genes(seg-sei, ser), and 42.94% carried SEl genes(selj-selq, selu). The most frequently carried gene was sea (19.76%), followed by seg (19.15%), selo (19.15%), selm (16.94%), seln (16.33%), and sei (15.92%). Enterotoxin gene clusters(egcs) containing novel types of SE and SEl genes were found, including the egc:seg, selo, selm, seln, sei; the egc:seg, selo, selm, seln, sei, selu. Moreover, certain SE or SEl genes co-occur in the same strain, such as ser, sed, selj; sea, selk, selq; selk, selq. Those strains carrying novel seh gene were all methicillin-susceptible S. aureus (MSSA) strains. In local, the isolation rate of novel se and sel genes from S. aureus of different origins was significantly higher than that of classical se genes; thus, the detection of staphylococcal enterotoxin cannot be limited to the five classical se genes, also novel se and sel should be the focus of additional investigation.192 strains of Staphylococcus aureus had been analyzed by spa and MLST typing techniques, and 66 MRSA were also analyzed by SCCmec typing technique. The results showed that 45 ST types,59 spa types and 5 SCCmec types were found. The major genetic types of human-origin MRSA were CC239-t030-SCCmec Ⅲ, CC239-t037-SCCmec Ⅲ, ST630-t4549-SCCmec Ⅴ and ST630-t2196-SCCmec Ⅴ, nearly all the tool-origin MRSA were identied to ST630-t4549-SCCmec V, the whole of cow-orign MRSA were identied to ST630-t2196-SCCmec Ⅴ, and all the pig-origin MRSA were distributed in CC9, those untypable MRSA were identied to ST9-t899 and ST2630-t1939. The sea-selk-selq, selk-selq and sea-selq were widely distributed in CC239-SCCmecIII MRSA, CC9-MRSA contained selk-selq, and CC5-MSSA also carried the sea-selk-selq. CC5-SCCmec II MRSA brought the seg-sei-selm-seln-selo and the egc (seg-sei-selm-seln-selo-selu) is harboured by CC1301-SCCmec V MRSA, but these two egcs tended to occur in those MSSA from CC5、CC25, CC30, CC45 and CC1301 frequently. This study showed that SE genes especially egcs could be harboured by certain strains had special genetypes, and some releated to MRSA.