| Objective : To understand the clinical distribution,drug resistance,epidemic types and carrying situation of virulence gene of methicillin-resistant Staphylococcus aureus(MRSA)in our hospital,and to analyze the clinical characteristics of MRSA bloodstream infection and the risk factors affecting the prognosis,so as to provide suggestions for clinical rational drug use and infection control.Method:(1)461 strains of MRSA isolated from the hospital from January 2015 to December2019 were retrospectively analyzed in the aspects of the source of specimens,the distribution of departments,the changing trend of detection rate and drug resistance rate.The drug resistance of 461 strains of MRSA and 1007 strains of methicillin sensitive Staphylococcus aureus(MSSA)were compared and analyzed.(2)The clinical features and risk factors of poor prognosis of MRSA bloodstream infection in a hospital from July 2014 to July 2020 were retrospectively analyzed.(3)53 strains of MRSA and 39 strains of MSSA were collected from June 2020 to December 2020.The SCCmec epidemic types of MRSA in our hospital were analyzed by multiplex PCR,and the virulence genes(hla、hlb、sea、seb、pvl、tst and fnb A)of MRSA and MSSA were compared by common PCR.Results:(1)The detection rates of MRSA from 2015 to 2019 were 40.70%,24.75%,26.83%,34.33% and 30.72%,with an average of 31.34%.MRSA was mainly distributed in ICU ward,cadre health care ward,neurosurgery,neurology and pediatrics,with the constituent ratios of17.35%,16.70%,15.84%,12.80% and 7.81%,respectively.The detection rate of MRSA in ICU was 64% which was significantly higher than 28.31% in non ICU(P<0.05).MRSA was mainly isolated from sputum,secretion,blood,pus and urine,with the constituent ratios of52.28%,20.61%,9.76%,5.42% and 4.34%,respectively.The detection rate of MRSA in sputum was 60.40%,the highest detection,which was significantly higher than 20.52% in non sputum samples(P<0.05).From 2015 to 2019,the drug resistance rates of MRSA to erythromycin,nitrofurantoin,linezolid,vancomycin and quinuptin/ dafurtin had little change(P>0.05);the drug resistance rates to gentamicin,rifampicin,ciprofloxacin,levofloxacin,moxifloxacin,clindamycin and tetracycline showed a downward trend(P<0.05).The 5-year average drug resistance rate was 50%-100%;the resistance rate to cotrimoxazole showed an upward trend(P<0.05).Compared with MSSA,MRSA had higher resistance rates to penicillin,gentamicin,rifampicin,ciprofloxacin,levofloxacin,moxifloxacin,clindamycin,erythromycin,nitrofurantoin and tetracycline(P<0.05).However,the resistance rate of MSSA to cotrimoxazole was significantly higher than that of MRSA(P<0.05).(2)From July 2014 to July 2020,there were 111 patients with SA bloodstream infection,including 42(37.80%)with MRSA infection and 69(62.20%)with MSSA infection.The average age(67.88±14.79 years old),length of stay(23.50 days),medical expenses(110112.73 yuan),mortality(35.71%)and poor prognosis(54.76%)of MRSA group were significantly higher than those(56.78±15.51 years old,14.00 days,19684.14 yuan,13.04% and 17.39%)of MSSA group(P<0.05).Old age(≥ 65 years),respiratory failure,anaemia,deep venous catheterization,indwelling urinary catheter,indwelling gastric tube,endotracheal intubation,ICU admission,carbapenems,glycopeptides,antifungal drugs,third generation cephalosporins,antibiotics(≥3 kinds)and hormones were higher in MRSA group than those in MSSA group(P<0.05).Multivariate analysis showed that respiratory failure was independent risk factor for poor prognosis of MRSA bloodstream infection.(3)Among the 53 MRSA strains collected,48 confirmed MRSA strains were classified into 31(64.58%)strains of SCCmecⅢ,7(14.58%)strains of Ⅳa,4(8.33%)strains of Ⅴ and 6(12.50%)unclassified strains.The resistance spectrum of SCCmec III MRSA was the most extensive,followed by SCCmec IVa and SCCmec V.(4)The carrying rates of hlb,tst,sea,seb,pvl,hla and fnb A genes in 48 MRSA strains were 93.75%(45/48),39.58%(19/48),16.67%(8/48),27.08%(13/48),47.92%(23/48),95.83%(46/48)and 95.83%(46/48),respectively.The positive rates of pvl,tst,hla and sea in MRSA group were significantly higher than those in MSSA group(P < 0.05).The proportion of MRSA strains carrying 4 or more virulence genes was 79.17%,which was significantly higher than that of MSSA strains(33.33%)(P < 0.05).(5)The MRSA samples with more virulence genes were sputum and secretion,and the departments with more virulence genes were neurosurgery and respiratory department.Almost all of the SCCmecⅢMRSA strains carried hla,hlb and fnb A genes,some carried pvl and tst genes,and a few carried sea and seb genes.Conclusions:MRSA was mainly distributed in ICU,and sputum was the main source of samples.MRSA infection decreased slightly in the past five years,but the detection rate of MRSA remained at about 30%,showing multiple drug resistance.MRSA infection increased hospital stay,medical costs,mortality and poor prognosis.Respiratory failure is an independent risk factor for poor prognosis of MRSA bloodstream infection.The MRSA strains in our hospital carry a large number of virulence genes,and the carrying rate is high,especially in the department of respiratory and neurosurgery.Virulence genes mostly come from sputum and secretion specimens.SCCmecⅢ is the main epidemic type,and it is spread between hospitals and communities.Therefore,the hospital should strengthen the management of antibiotics,bacterial resistance monitoring,hand hygiene and disinfection and isolation measures to effectively control the infection and drug resistance of MRSA.. |
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