Institutional outbreak involving multiple clades of IMP-producing Enterobacter cloacae complex sequence type 78 at a cancer center in Tokyo, Japan

Abstract Background Information about the clinical and microbiological characteristics of IMP-producing Enterobacterales has been limited. Here, we describe an institutional outbreak Enterobacter cloacae complex (ECC) involving multiple clades ECC sequence type (ST) 78 strains. Methods Antimicrobial susceptibility testing, whole-genome sequencing, conjugation experiments 18 strains isolated during four-year study period were performed. Species subspecies determined by average nucleotide identity analysis clonal relatedness isolates was analyzed with multilocus typing core-genome single polymorphism (SNP) analysis. Relevant information extracted from medical records. Results Fourteen as hormaechei ST78. Sixteen isolates, including 13 belonging to ST78, carried bla IMP-1 in In316-like class 1 integron also IncHI2 plasmids. Conjugation successful for 12 carrying on plasmids isolate IMP-11 IncL/M plasmid. Although isolation ST78 clustered a 14-months suggesting nosocomial transmission, these subdivided into three SNP analysis: clade A ( n = 10), B 1), C 3). part unexpected epidemiological at time Most susceptible non-β-lactam antibiotics had relatively low minimum inhibitory concentrations carbapenems (≤4 μg/mL). Five six infections caused treated successfully. Conclusions Whole-genome sequencing revealed different strains, where patients favorable treatment outcome compared that producing other carbapenemases, possibly due their non-multidrug-resistant phenotype.