The Microbiological Characteristics of Carbapenem-Resistant Enterobacteriaceae Carrying the mcr-1 Gene

This study aims to assess the prevalence of the gene among carbapenem-resistant (CRE) isolated from clinical specimens and to further investigate the clinical significance and microbiological characteristics of CRE carrying the gene. Four hundred and twenty-three CRE isolates were screened for the presence of the gene. After identification, their clinical significance, antibiotic susceptibility, and antibiotic resistance mechanisms including the ESBL gene, carbapenemase gene, outer membrane protein (OMP), and plasmid sequencing were assessed. Only four (0.9%) isolates of carbapenem-resistant were found to carry the gene and demonstrated different pulsed-field gel electrophoresis (PFGE) patterns and sequence types (ST). While one patient was considered as having -positive carbapenem-resistant (CREC) colonization, the other three -positive CREC-related infections were classified as nosocomial infections. Only amikacin and tigecycline showed good in vitro activity against these four isolates, and three of them had a minimum inhibitory concentration with colistin of ≥4 mg/L. In the colistin-susceptible isolate, was nonfunctional due to the insertion of another gene. In addition, all of the mcr-1-positive CREC contained various resistant genes, such as , , , , and . In addition, one strain (EC1037) had loss of the OMP. The emergence of the gene among CRE, especially , remains worth our attention due to its resistance to most antibiotics, and a further national survey is warranted.