A Study On The Resistance Mechanism And Homology Of Carbapenem-resistant Serratia Marcescens In A Tertiary Hospital And Analysis Of Risk Factors For Clinical Infection

Object:To study carbapenemase carrying cases of the clinical isolates of Serratiamarcescens carbapenems-resistance and investigate molecular epidemiological characteristics of these strains.At the same time,analysis of clinical features of drug-resistant bacteria and risk factors associated with infection.To guide the clinical use of antimicrobial drugs correctly,and provide scientific basis of prevention and control of infection.Methods:Collected of Serratia marcescens strains from patients without repeats in atertiary hospital from January to September 2017,identification of bacteria using Vitek2 Compact automated microbiological analysis system and matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF-MS),then used Vitek-2 Compact automatic microbial system for drug susceptibility testing.Using a modified Hodge test to detected carbapenemase from the phenotype.PCR was carried out for analyzing the carbapenemase genes and extended-spectrum?-lactamases genes.Then the positive products were sequenced and campared to the blast.Pulsed Field Gel Electrophoresis(PFGE)and Enterobacterial repetitive intergenic consensus PCR(ERIC-PCR)were used for DNA typing and testing of homology.We collected Serratia marcescens clinical isolates and the data of patients.According to carbapenems are divided into Serratia marcescens no sensitive group(including drug resistance and intermediary)and sensitive group,The Chi-squre(?~2)test and Logistic regressions were performed to analyze clincial risk factors.Results:At last,Serratia marcescens carbapenem non-sensitive 30 strains andsusceptible strains 15 strainswere obtained by screening,mainly distributed in the ICU and the Department of neurosurgery,the most of deep sputum.Drug sensitive testing showed that most of the antibiotics are not sensitive,the higher the sensitivity rate of amikacin,trimethoprim/sulfamethoxazole.Ciprofloxacin,gentamicin,aztreonam,ceftria-x one have a huge resistance rate.Twenty-two positive strains were detected by the modifed Hodge test.The blaCTX-M-14 was detected in 21 strains,the blaKPC-2 was detected in 14 strains,the blaTEM was detected in 6 strains,the blaNDM-1was detected in 1 strain,the blaSHV was detected in 1 strain of S.marcescens.Meanwhile,the emergence of a bacteria containing a variety of resistance genes.Neither carbapenemase genesnorextendedspectrum?-lactamase genes were detected in 6 strains.The Chi-squre(?~2)test and logistic regressions were used to analyze the independent risk factors of artificial airway and mixed infection as carbapenem resistant Serratia marcescens.Conclusion:The clinical isolates of S.marcescens carbapenems-resistant in a tertiary hospitalwere serious in drug resistance.Production of KPC-2 and CTX-M-14 carbapenemases is an important mechanism of resistance to carbapenem antibiotics.14 of 30 carbapenem-resistant strains were identified to the same type.This indicates that may spread in the hospital.Effective measures are urgently needed for early identification and control to prevent the spread of these carbapenemase-resistance S.marcescens.At the same time,the implementation of artificial airway and mixed infection were carbapenem-resistant clinical risk factors.Clinical attention should be given to enhance aseptic technique,hand hygiene of medical staff and standard use of antibacterial drugs to reduce the infection rate and mortality of resistant Serratia marcescens,and prevent the widespread of resistant bacteria in the hospital.