Study On Detection Of Bofilm Genes And Antimicrobial Resistance Of Staphylococcus Aureus Isolated From Cow In Ningxia

Staphylococcus caurezus is one of the main pathogens of dairy cow mastitis.In recent years,drug resistance and multi-drug resistance increased rapidly due to the extensive use of antibiotics,especially after the formation of Staphylococcus aureus biofilm,which improving the drug resistance,evading the immune function,Long-term survival and causing chronic infection.So,there were a lot of mastitis cows infection repeadly and treatment difficulty.This study on biofilm-forming ability and mechanisms of Staphylococcus aureus will help to provide new ideas for prevention and treatment clinical mastitis.During the study,Staphylococcus aureus were separated and identified from bovine mastitis samples of clinical and subclinical cases,which were collected from the cow farms in NingXia.The Staphylococcus aureus were isolated and identified by the methods including gram staining microscopy,CHROMagar Staphylococcus aureus agar and PCR amplification for 16S rDNA gene and nuc gene.After that,according to broth microdilution method recommended by the CLSI standards committee,the isolated strains of Staphylococcus aureus were tested for MIC.The results showed that the sensitive rate of Staphylococcus aureus to vancomycin,doxycycline reached more than 90%,the sensitivity rates of ceftiofur,gentamicin,tetracycline,ciprofloxacin and norfloxacin were higher than 80%.The resistance rates of ampicillin and penicillin were about 60%.The 3,4 resistant strains were dominant,the proportions of these strains were 13.6%and 15.5%,respectively.The isolated strains tolerated up to 10 kinds of antimicrobial agents mostly.The biofilm of Staphylococcus aureus was cultured by Congo red method,and the biofilm formation ability was measured by crystal violet dyeing method.The results showed that 181 strains of 265 Staphylococcus aureus formed biofilm and the positive rate was 68.3%.Among 181-positive biofilm strains,weak adhesion,moderate adhesion,the adhesion strength detection rates were 47.5%,30.4%,22.1%,respectively.The biofilm-related genes of 265 Staphylococcus aureus isolates were detected by PCR.The results showed that the detection rates of sigB,sar,agr,icaA,icaD and icaR were 91.7%,77.4%,57.4%,72.5%,87.2%and 90.6%,respectively.In this study,we analyzed the antimicrobial resistance and detected the biofilm of Staphylococcus aureus in Ningxia.The results revealed initially the drug resistance and prevalence of biofilm of bovine Staphylococcus aureus in Ningxia.It provides a theoretical basis to guide the rational use of antimicrobial agents in veterinary clinic and lays the foundation for further study of bacterial biofilm.