ABSTRACT
Objectives:To investigate the genetic characteristics of the blaNDM-1-carrying plasmid of the multidrug resistant Enterobacter hormaechei subsp. hoffmannii clinical isolate C37, and constructing a phylogenetic tree of the 66 publicly available genomes of the Enterobacter hormaechei subsp. hoffmannii to explore its global epidemic situation. Methods:Carbapenem-resistant Enterobacter cloacae complex (CRECC) strains isolated from the First Affiliated Hospital of Sun Yat-sen University from August 2014 to August 2021 were collected. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) and 16S rDNA Sanger sequencing were used for species identification. Micro broth dilution method was used for antibacterial susceptibility test. The polymerase chain reaction (PCR) was used to detect the β-lactamase resistance gene and plasmid-mediated quinolone resistance (PMQR) gene carried by the C37 strain. The conjugation experiment was used to confirm the conjugative metastasis of the resistance genes in C37 strain. Whole genome of the C37 strain was sequenced. Core genome was extracted and the phylogenetic analysis of 66 publicly available Enterobacter hormaechei subsp. hoffmannii was performed. Results:Enterobacter hormaechei subsp. hoffmannii C37 strain is resistant to third-generation cephalosporins, carbapenems, aminoglycosides and quinolones, and carries blaACT-5, blaNDM-1, qnrA1, aac(6′)-Ib-cr, oqxAB, fosA, dfrA15 and other resistance genes, as well as IncX3, IncX4, IncFIB and IncFII plasmids. Multilocus sequence typing (MLST) analysis showed that C37 strain belongs to the ST78 type of Enterobacter cloacae complex (ECC). Conclusions:ST78 type Enterobacter hormaechei subsp. hoffmannii is closely related to the spread of carbapenem resistance genes. It is a potential high-risk clone to spread carbapenem resistance genes. The prevalence and trends of ST78 type Enterobacter hormaechei subsp. Hoffmannii should be monitored.
ABSTRACT
In order to deal with the increasing number of multidrug resistant Enterobacteriaceae , polymyxins were re-introduced into clinical practice .The resistance of polymyxins had gained global attention.In addition to chromosomal mediated drug resistance , a new plasmid-mediated colistin-resistance gene mcr-1 made transferation of polymyxins resistance more easily .Here, the mechanisms of chromosome mediated polymyxin resistance and plasmide-mediated drug resistance , including the distribution , prevalence, transfer mechanism, and genetic environments of mcr-1, current methods for polymyxins susceptibility testing methods and novel qualitative detection techniques were reviewed to provide information to cope with the growing problem of bacterial drug resistance .