Studies On Antimicrobial Resistance Of Staphylococcus Aureus From Calves And The Resistance Elimination By Thymol

In order to elucidate the drug resistance of Staphylococcus aureus of calf origin and its resistance mechanism in Inner Mongolia,and to explore the elimination of drug resistance of active ingredients of Chinese medicine on Staphylococcus aureus of calf origin in the context of restriction and prohibition of resistance,the study was carried out on the isolation and identification of Staphylococcus aureus of calf origin,the analysis of drug resistance and the elimination of drug resistance of thymol on it.In this study,the isolation and identification of Staphylococcus aureus was carried out using biochemical identification and molecular biology identification methods on the collected calf disease material;the in vitro susceptibility of the isolates to 18 antibacterial drugs was determined by drug sensitivity testing using the K-B method: the carriage of relevant resistance genes and virulence genes was detected by PCR;the biofilm forming ability of the isolates was determined by crystalline violet staining;and the biofilm forming ability of the isolates was determined by micro-broth dilution method.The MIC values of thymol on the isolates were determined by micro-broth dilution method,and the strains were subjected to resistance elimination test after interaction with thymol.Forty-three strains of Staphylococcus aureus of calf origin were isolated and identified,with an isolation rate of 41.3%.The isolates were resistant to ampicillin(100%),cefoxitin(90.7%),cotrimoxazole(81.4%),kanamycin(60.5%)and susceptible to ciprofloxacin(9.3%).β-lactam resistance genes were detected in the highest number,with bla Z detected at 90.6% and nor A and nor B detected at the same rate of 81.3%.Among the virulence genes,hla had the highest detection rate of 58.1%,hlb 27.9% and pvl 18.6%,while the remaining virulence genes were not detected.The percentages of strains with strong,moderate,weak and no biofilm forming ability were 23.2%,32.5%,16.3% and30% respectively.83.9% of the biofilm positive strains were multi-drug resistant strains.The results of the resistance elimination test showed that thymol was effective in eliminating the resistance of strains 17 and 24 and restoring their susceptibility to cefotaxime after 72 h of passaging.In conclusion,the results of the drug-sensitive paper test showed that the drug resistance in Inner Mongolia is more serious and there is a positive relationship between drug resistance and drug resistance genes;the multiple drug resistance of biofilm-positive strains is more serious than biofilm-negative strains;the resistance of calf-derived Staphylococcus aureus to antibacterial drugs is reduced after thymol treatment,and thymol can be used clinically to reduce drug resistance and thus improve the cure rate of related calf diseases.