Study On The Resistance Mechanisms And Clinical Risk Factors Of Carbapenem-resistant Enterobacteriaceae Isolates

ObjectivesTo investigate the resistance mechanisms and clinical risk factors of Carbapenem-Resistant Enterobacteriaceae Isolates of Fujian Medical University Union Hospital.MethodsA total of168CRE strains were collected from Fujian Medical University UnionHospital. Antibiotic susceptibility（ETP and IMP）was performed to select thestrains． The Modified Hodge Test (MHT) and the Combination Disk Test were usedfor carbapenemase phenotype screening. The Minimum Inhibit Concentration wasdetected using agar dilution method for17drugs. PCR and DNA sequencing wereused to detect common β-Lactamase genes, caebapenemases genes and AmpC genes,and of the postive isolates were sent to sequence. ERIC-PCR was used to analyse thehomology. Conjugation experiments demonstrated the transferability of thecarbapenem-resistant determinants. Finally, Case study of patients with CRE was usedto analysis risk factors.Results109CRE included41strains of Klebsiella pneumonia,29Enterobacter cloacae,21Escherichia coli,5Morganella morganii,5klebsiella oxytoca,5proteus mirabilis，2serratia marcescens,1Enterobacter aerogenes and1Klebsiella oxytoca. Therewere70isolates positive detected by MHT, the combination disk test showed34only produced metallo-enzyme carbapenemase and11isolates only produced KPCcarbapenemase, one isolate contained the two above enzyme. Minimum inhibitconcentration was detected by using agar dilution method for17drugs. Resistancerates of41strains of Klebsiella pneumonia,29Enterobacter cloacae,21Escherichia coli to Ertapenem and Imipenem were97.6/73.2、75.9/62.1、76.2/57.1, to Cefoxitin,cephalosporin and Aztreonam were100%,90%and90%respectively. Resistancerates of the remaining18CRE strains to Imipenem was94.4%, all were sensitive toMeropenem.41strains of Klebsiella pneumonia,29Enterobacter cloacae and21Escherichia coli could be classified into33,23and13types by ERIC-PCR.33isolates conjugated successfully of54Carbapenem-Resistant EnterobacteriaceaeIsolates with carbapenemases gene.40isolates were only IMP producers, IMP-4weredetected in26isolates, the others were IMP-8(14strains).7strains only producedKPC, all were KPC-2. Four isolates only produced NDM-1.And one strain producedIMP-4and NDM-1simultaneously. Two strains produced IMP-8and KPC-2simultaneously.66strains produced TEM, and all were TEM-1.48strains producedSHV, including SHV-12(20strains), SHV-11(14strains), SHV-26(7strains),SHV-28(2strains)，SHV-31(2strains)，SHV-1(1strains)，SHV-2(1strains) andSHV-33(1strains).24strains produced CTX-M-9groups, including CTX-M-14(17strains)，CTX-M-65(7strains).17strains produced CTX-M-1groups, includingCTX-M-115(7strains)，CTX-M-79(5strains), CTX-M-3(3strains), CTX-M-22(2strains).10strains produced AmpC, including CIT(7strains), MOX(2strains), onestrain produced both EBC and CIT.65(69.15%) patients had changed sickbeds onceor more times, and27with three or more than three times. All except three patientshad invasive operations.53(56.38%) patients simultaneously were detected with othermultiple drug-resistant strains. During hospitalization, the use of antibiotics are asfollows: the numbers of patients using carbapenems, quinolones, aminoglycosides,cephalosporins, lactams and other types of drugs (such as tetracyclines,antituberculotic drugs, oxazolidinone, fosfomycin class, and vancomycin againstfungi, etc.) were47.87%(45/94),44.68%(42/94),24.47%(23/94),55.32%(52/94),57.45%(54/94),42.55%(40/94).ConclutionsCRE strains isolated from Fujian Medical University Union Hospital were mainlyKlebsiella pneumonia, were mostly pan-resistant strains. The main reason was metallo-enzyme carbapenemase. The resistant isolates were not clonal transmission.Sickbeds changed and invasive operation were risk factors for CRE strains infection.