Molecular epidemiological analysis and risk factors for acquisition of carbapenemase-producing Enterobacter cloacae complex in a Japanese university hospital

Background: To clarify the molecular epidemiology of carbapenem-resistant Enterobacter cloacae complex (CREC) and the risk factors for acquisition of carbapenemase-producing E. cloacae complex (CPEC). Methods: Using clinical CREC isolates detected in a Japanese university hospital over 4 years, carbapenemase production was screened with phenotypic methods. Carbapenemase genes were analysed by PCR and sequencing. Molecular epidemiological analyses were conducted with repetitive extragenic palindromic (REP)-PCR and multilocus sequence typing (MLST). CRECs were identified to the subspecies level by hsp60 sequencing. Whole-genome sequencing of plasmids was conducted. A case-control study was performed to identify risk factors for acquisition of CPEC among patients with CREC. Results: Thirty-nine CRECs including 20 CPECs carrying bla(IMP-1) were identified. Patients with CPEC had longer hospital stay before detection (26.5 days vs. 12 days, p=0.008), a urinary catheter (odds ratio [OR], 5.36; 95% confidence interval [CI], 1.14-30.9; p=0.023), or intubation (OR, 7.53; 95% CI, 1.47-53.8; p=0.008) compared to patients without CPEC. Four genetically closely related CPEC clusters were observed, which showed that three of four CPEC clusters corresponded to E. asburiae (ST 53), E. hormaechei subsp. steigerwaltii (ST 113 and ST 1047) and E. cloacae subsp. cloacae (ST 513) by MLST and hsp60 sequencing. Seven representative plasmids shared structures with class I integron containing bla(IMP-1) and IncHI2A replicon type. Conclusions: A longer hospital stay, presence of a urinary catheter, and intubation are risk factors for CPEC acquisition. In addition to horizontal transmission of genetically indistinguishable CPECs, IncHI2A plasmid carrying bla(IMP-1) appeared to be transferred among genetically different ECs.