Purpose: Antimicrobial resistance, especially carbapenem resistance Enterobacteriaceae and plasmid mediated mobile colistin resistance, is a serious issue worldwide. This study was designed to determine the epidemiological characteristics of plasmid mediated colistin resistance and carbapenem resistant Enterobacteriaceae from tertiary A hospital located in Hefei, China.
Methods: Totally, 158 carbapenems resistant Enterobacteriaceae (CRE) were screened for antibiotic susceptibility, mcr-1 , extended spectrum β-lactamases (ESBLs), metallo-β-lactamases (MBLs), and fosfomycin resistance genes using PCR and sequencing. The sequence types were identified by multilocus sequence typing (MLST). Plasmid profiles were determined by PCR based replicon typing (PBRT), and the plasmid sizes were confirmed by southern blotting.
Results: The isolates showed high MIC₅₀ and MIC₉₀ for all antimicrobials, except tigecycline, meropenem, and colistin. The main Carbapenemase genes were bla _KPC-2 (90.5%), bla _NDM-1 (3.7%), bla _OXA-48 (5.6%) and fosA3  (14.5%). The bla _CTXM-15 found 36.7%, mcr-1  (3.7%) recorded in six isolates. PBRT revealed bla _KPC-2 in K. pneumoniae  on IncR, IncFII, and IncA/C. bla _NDM-1 in E. coli  on IncFII, whereas in E. cloacae  noticed on IncHI2 plasmid. mcr-1  was recorded among IncFIIK, IncFII, and IncF in E. coli, K. pneumoniae , and E. cloacae . Resistance genes (mcr-1, bla _NDM-1, bla _KPC-2) harboring plasmids are successfully trans-conjugant to EC-600 . A high incidence of ST11 was observed in K. pneumoniae  carbapenem resistant isolates. While in E. coli , multiple STs were identified. However, mcr-1  in ST23 was identified for the first time in Anhui Province. Among Enterobacter cloacae , ST270 detected carrying bla _NDM-1. Southern-hybridization confirmed the plasmid sizes 35– 150kb.
Conclusion: This study indicates the co-carrying of mcr-1, bla _KPC-2, and bla _NDM-1 among clinical isolates, the prevalence of different Enterobacteriaceae STs is alarming, especially in E. coli . Holding such a resistance profile is a threat for humans and animals, which may be transferred between the strains through plasmid transfusion. Persistent control actions are immediately necessary to combat this hazard.
Keywords: ESBL, MBL, KPC2, mcr-1, NDM-1, CTXM-15