Drug Resistance And Molecular Epidemiology Of Staphylococcus Aureus

ObjectiveTo investigate the drug-resistance and its changes of Staphylococcus aureus(S.aureus),which were isolated from a tertiary hospital,and to investigate the transmission of S.aureus,and to investigate the genes encodingPanton-Valentine leukocidin(PVL)and Toxic shock syndrome toxin-1(TSST1),which were named pvl and tst,and provide some references for the control and treatment of S.aureus infection.Methods1.We collected all the data of non-repetitive S.aureus isolated from Shanghai 10th People's Hospital from 2016 to 2018 and analyzed its drug susceptibility results.2.We chose 168 non-repetitive S.aureus strains from September 2016 to May 2018 in a completely randomized design.Pulsed-field gel electrophoresis(PFGE)was used to analyze the homology between strains.3.Polymerase chain reaction(PCR)was used to investigate the pvl and tst genes.Results1.The drug-resistanceand its changes of S.aureusThere were 711 non-repetitive S.aureus strains between 2016 and 2018,and the proportion of MRSA was 60.19%,59.82%and 56.98%,respectively.The strains were mainly collected from neurosurgery,emergency ward,ICU and general surgery department.MRSA showed multi-drug resistance and higher resistance rate than MSSA,both of which were 100%sensitive to linezolid,and no vancomycin-resistant S.aureus was found.MSS A shows high sensitivity to antibiotics except penicillin.In 2016-2018,we found the resistance of MRSA declined in erythromycin,minocycline,ciprofloxacin,gentamicin and levofloxacin and increased in clindamycin,compound sulfamethoxazole and no obvious change in rifampicin and tetracycline.We also found the resistance of MSSA declined in erythromycin,ciprofloxacin,gentamicin and levofloxacin,increased in clindamycin,no obvious change in rifampicin and tetracycline.2.The PFGE typingThe PFGE divided the 168 S.aureus strains into 24 clonal types,C7 type included the most strains and C4 and C6 were next types.C7 was the main clono type of neurosurgery(50%)and continuously found in 15 departments.3.The pvl and tst genesThere were 32.3%strains carrying pvl and 10.2%carrying tst and 4.8%carrying both.There were 28.6%MRSA carrying pvl and 35.5%in MSSA,and the difference was not statistically significant.There were 17.9%MRS A carrying tst and 3.2%in MSS A,and the difference were statistically significant.In this study,strains carring pvl gene or tst gene had no significant effect on stay days,but strains carring tst gene had an effect on clinical outcome.Conclusion1.The detection of MRSA was decreased in the three years,but the resistance increased except vancomycin.2.Some S.aureus strains were found sustained transmissionby PFGE and we need more powerful measures to control the infection.3.High level carrying rates were found in pvl and tst genes in this hospital.The infections were observed more often on complicated patients.In the meantime,a lot of cases had the possibility of carring strains to community.It was complicated,and we need more research to assess its impact.