The Distribution Of Virulence Genes,Biofilm Formation And Coagulation Pathogenicity Of Porcine Staphylococcus Aureus

Staphylococcus aureus?S.aureus?is an important foodborne pathogen,which could cause outbreak of foodborne diseases and staphylococcal food poisoning.S.aureus is also part of the commensal microbiota of the human or animal population and could cause a range of illnesses.In this study,a total of 130 S.aureus isolated from nasal swabs and environment samples obtained from swine farm,fresh pork samples obtained from slaughterhouse and terminal markets were studied.The distribution of virulence genes,including staphylococcal enterotoxins?SE?genes,hemolysin genes,toxic shock syndrome toxin?tst?,exfoliative toxins?eta,etb?,Panton-Valentine leucocidin?pvl?,as well as adhesion and biofilm-producing genes,were determined by PCR.The agr typing was determined by multiplex PCR.Quantification of biofilm formation was performed by spectrophotometry in microplates using crystal violet staining.Coagulation adaptability of those isolates to rabbit,bovine and goat plasma were studied by coagulase assays,as well as the distribution of staphylococcal coagulase genes of vwb^C,vwb^Sbo4,vwb^Sov2 and vwb^Seq1eq1 in 130 S.aureus were investigated by PCR.At the same time,the association of different experimental results were analyzed by using statistical analysis.The results are as follows:a)Among 130 S.aureus,approximately 94.6%?123/130?S.aureus harbored SE genes,in which the most frequent SE gene was seb?60.0%?.The distribution of SE genes between swine farm isolates and slaughterhouse or terminal market isolates were significantly different.The classical SE genes?sea,seb,sec,sed,see?were relatively higher in raw meat isolates obtained from slaughterhouse or terminal market than swine farms isolates,suggesting that raw meat isolates have a greater potential for classical staphylococcal food poisoning.The novel SE genes were mainly distributed in swine farm isolates,showing that swine farm isolates harboring novel SE genes could be new potential risk factors for food safety.In addition,the hemolysin genes of hla,hlb,hld were found in 95.4%,100.0%,98.5%of all isolates,respectively.Moreover,both eta and etb were detected in only one slaughterhouse isolate,whereas pvl and tst genes were not found in any of the isolates,respectively.b)By multiplex PCR,the agr types were successfully identified in 109?83.8%,109/130?isolates.The agr genotypes of S.aureus isolates,initially from the farm level through the slaughtering and retail levels,were diverse.All swine farms isolates belonged to agr IV,whereas the terminal market isolates mainly belonged to agr I?92.3%?.However,S.aureus isolated from slaughterhouse indicated diverse agr types,in which the most frequent agr genotypes was agr I.All isolates harbored adhesion and biofilm-producing genes and had the ability to form biofilms.In this study,biofilm production in TSB_glc was higher for raw meat isolates compared to swine farms isolates,because there was a significant difference in the prevalence of several genes involved in adhesion and biofilm production between raw meat and swine farms isolates?p<0.05?.In addition,agr-positive isolates had a higher number of toxin genes than agr-negative isolates?p<0.05?,and agr I more likely to be strong biofilm producers compared with other agr types isolates.There was a statistically negative correlation between biofilm formation capacity and multi-drug-resistance,that is strong biofilm formation likely contained larger proportion of non-multidrug-resistant isolates.c)The positive coagulation rates of 130 S.aureus to rabbit,bovine and goat plasma were100.0%,28.5%,28.5%,respectively.The staphylococcal coagulase genes of vwb^C,vwb^Sbo4and vwb^Sov2ov2 were identified in 100.0%?130/130?,26.9%?35/130?and 26.9%?38/130?of all isolates,respectively.None of isolates harbored vwb^Seq1eq1 gene.This study showed that porcine S.aureus possessed coagulation pathogenicity to different animal hosts,and the detection rates of vwb^Sbo4 and vwb^Sov2ov2 genes and the positive coagulation rates of bovine and goat plasma of S.aureus isolated from swine farms were significantly higher than those isolated from slaughterhouse and terminal marker isolates?p<0.05?.