Genotype and homology analysis of methicillin-resistant Staphylococcus aureus in critical care
Objective:To understand the changes in drug resistance of Staphylococcus aureus in patients with lower respira-tory tract infections in the Department of Critical Care Medicine,Congjiang County People's Hospital,Guizhou Province,to un-derstand the main drug-resistant genes and disinfectant-resistant genes of methicillin-resistant Staphylococcus aureus,and to ana-lyze some strains Perform homology analysis.Methods:This study retrospectively analyzed the changes in Staphylococcus aureus drug resistance in patients with lower respiratory tract infections in the Department of Critical Care Medicine,Congjiang County People's Hospital,Guizhou Province from 2018 to 2021,and used correlation analysis(pearson)statistical methods to explore the relationship between bacterial resistance and antibacterial drugs medication frequency(defined daily dose system,DDDs).Totally 40 strains of methicillin-resistant Staphylococcus aureus were isolated from specimens submitted by patients with lower respiratory tract infections in the Department of Critical Care Medicine over the past four years were used as the research objects.Instrumental methods were used to identify the test strains and their drug susceptibility,and PCR technology was used to determine the resis-tance genes(mecA,SCCmec,femB)and disinfectant resistance genes(qacA/B)detection.Multilocus sequence typing(MLST)method was used to analyze the homology of 40 strains of test bacteria.Results:The annual average resistance rate of Staphylococ-cus aureus shows that the penicillin resistance rate has always been higher than 92%.The resistance rates to tetracycline,clindamy-cin,and cotrimoxazole continued to increase again after declining in 2019.The resistance rates of erythromycin,oxacillin,levo-floxacin,and quinupristin/dalfopristin shows an increasing trend year by year.No strains resistant to linezolid,vancomycin,and ti-gecycline were found.Correlation analysis shows that there is a significant positive correlation between the penicillin resistance rate and oxacillin DDDs(r=0.99,P<0.05),there is a significant negative correlation between the oxacillin resistance rate and eryth-romycin DDDs,etc.,and the resistance rates of other antibacterial drugs.There is no statistical significance in the correlation with DDDs of each drug.Genetic testing found that the detection rate of mecA in 40 strains of resistant MRSA was 97.5%,the SCC-mec and femB genes were not detected,and the detection rate of qacA/B genes was 15%.The MLST typing results show that there are 7 sequence types in total,among which ST59 type has the highest proportion and is the dominant type,accounting for 42.5%,followed by ST45 type,accounting for 25%,ST239 type,ST28 type,ST188 type,ST1 type and ST630 account for 12.5%,7.5%and 5%,5%and 2.5%respectively.Conclusion:The drug resistance rate of Staphylococcus aureus in lower respi-ratory tract infections in the Department of Critical Care Medicine is increasing year by year,and the antibiotics available are limit-ed.The development of bacterial resistance is related to the frequency of drug use.Carrying the mecA and qacA/B genes is the main reason for the development of drug resistance in methicillin-resistant Staphylococcus aureus.MLST results indicate the pres-ence of intrafamily clonal strains in the ICU ward.
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