Study On Drug Resistance Genes And Molecular Epidemiology Of Carbapenem-Resistant Serratia Marcescens

Objective 1.To investigate the clinical distribution characteristics of carbapenem-resistant Serratia marcescens isolated from the First Affiliated Hospital of Anhui Medical University and its sensitivity to common antibiotics;2.To explore the clonal typing of carbapenem-resistant Serratia marcescens and to understand its molecular epidemiological characteristics;3.Screening for the carbapenemase and carbapenemase genes carried by the bacteria;4.Provide theoretical guidance and scientific basis for clinical anti-infective treatment and prevention and control of nosocomial infection.Methods 1.Serratia marcescens resistant to any of carbapenem antibiotics(imipenem,ertapenem,meropenem)was collected from the Microbiology Department of the Laboratory of the First Affiliated Hospital of Anhui Medical University from January 2014 to December 2017,and repeated isolates from the same patient were removed;2.Vitek-2 Compact automatic microbial identification analyzer was used to identify bacteria.Matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF-MS)was used to verify the bacterial identification to ensure the accuracy of the selected strains;3.Vitek-2 Compact automatic microbial identification analyzer and GN identification card were used to detect the susceptibility of common clinical antimicrobial agents by MIC method or K-B method recommended by CLSI;4.The Enterobacterial repetitive intergenic consensus(ERIC)was detected by polymerase chain reaction(PCR)for clonal analysis of the resistant strain;5.The carbapenemase carried by the bacteria was screened by modified carbapenem inactivation method(m CIM),Carba NP test and modified Hodge test(MHT);7.Carbapenemase genes bla KPC,bla GES,bla IMI,bla NMC,bla SME-IRS,bla NDM,bla VIM,bla IMP,bla OXA-24,bla OXA-23-like,bla OXA-48-like,bla OXA-51-like,bla OXA-58-like were detected by PCR.Results 1.67 strains of Carbapenem-resistant Serratia marcescens were obtained after identifying and re-checking,and repetitive isolates were removed from the same part of the same patient.The main sources were intensive care unit(ICU),cadre's ICU,neurosurgery,and mainly from sputum samples;2.67 isolates of carbapenem-resistant Serratia marcescens were 100% resistant to cefotaxime and ceftriaxone;the resistance rates to imipenem,meropenem,ertapenem and aztreonam were respectively 94.03%,95.52%,98.51%,97.01%;resistance rates to ciprofloxacin,gentamicin,tobramycin,piperacillin/tazobactam,ceftazidime,cefepime,levofloxacin were all greater than 60 %;resistance rates to amikacin and cotrimoxazole were 5.97% and 7.46%,respectively;3.ERIC-PCR genotyping showed that 67 strains of Carbapenem-resistant Serratia marcescens could be divided into 8 types(expressed as A-H).Among them,50 strains of type A were the most,5 strains of type B,5 strains of type C,3 strains of type D,1 strain of type E,F,G and H,respectively;4.The positive rates of carbapenemase screening by bacteria in m CIM test,Carba NP test and modified Hodge test were 92.54%,89.55% and 91.04%,respectively;5.Among the 67 carbapenem-resistant Serratia marcescens,the carbapenemase gene was detected in 41 strains,and the detection rate was 61.19%.Among them,32 strains containing bla KPC gene and 7 strains containing bla OXA-23-like gene were detected.There are 7 strains of bla OXA-51-like gene,including 3 bla GES genes,including 1 strain of bla OXA-58-like gene,of which 8 strains contain multiple drug resistance genes.After comparison with the BLAST tool,it was confirmed that bla KPC was confirmed as bla KPC-2,bla OXA-23-like was confirmed as bla OXA-73,bla OXA-51-like was confirmed as bla OXA-106,and bla OXA-58-like was confirmed as bla OXA-58.The drug resistance genes bla IMI,bla NMC,bla SME-IRS,bla NDM,bla VIM,bla IMP,bla OXA-48,bla OXA-24-likewere not detected.Conclusion 1.Carbapenem-resistant Serratia marcescens origin departments of the First Affiliated Hospital of Anhui Medical University mainly consist of ICU,cadre ICU and neurosurgery department.The distribution trend of the departments is obvious.It is necessary to strengthen the infection prevention and control in the relevant departments;2.The sample source is mainly sputum specimens,suggesting that the infection caused by carbapenem-resistant Serratia marcescens is mainly affected by the respiratory system of patients;3.The isolated carbapenem-resistant Serratia marcescens is multi-drug resistant and highly resistant to common clinical antibiotics,and is only highly sensitive to amikacin and cotrimoxazole.It is suggested that amikacin or cotrimoxazole can be used as the drug of choice in cases where such bacterial infections are severe and there are limited antibiotics available;4.Carbapenem-resistant Serratia marcescens can be divided into 8 types(expressed as A-H),of which type A(50 strains)is the main epidemic strain,and the trend of clone concentration is obvious,suggesting that there may be an epidemic of type A clone strains in this hospital.Relevant departments should pay more attention to hand hygiene and disinfection,reduce unnecessary bed changes and referral between departments;5.Modified Hodge test,Carba NP test and m CIM test have similar detection rates of carbapenemase carried by Carbapenem-resistant Serratia marcescens,and each has its own advantages and limitations.Hospitals at all levels can flexibly choose to use them according to laboratory conditions;6.Carbapenemase genes of Carbapenem-resistant Serratia marcescens isolated in our hospital are mainly bla KPC-2 and bla OXA,and the same bacteria can carry many kinds of drug-resistant genes at the same time,suggesting that the drugresistant situation of the hospital bacteria is severe,it is necessary to strengthen prevention and control to block the spread of drug-resistant genes among different bacterial species.