First report of an Enterobacter cloacae ST837 resistant to cefiderocol co-harbouring blaIMP-19 and mcr 4.3 resistance genes, in Italy.

Abstract

Objectives: We described the molecular characterization of an Enterobacter cloacae strain resistant to cefiderocol, co-harbouring bla_IMP-19 and mcr-4.3 resistance genes METHODS: The strain was isolated from the rectal swab of a 77-year-old woman during the screening for the detection of patients colonized by carbapenemase-producing Enterobacterales (CPE), in Bologna (Italy). The strain was identified at the species level by MALDI-TOF mass spectrometry and the presence of IMP carbapenemase was confirmed both by a phenotypic immunochromatographic method, and by a rapid commercial NAAT. The strain underwent an antimicrobial susceptibility testing and its genome was fully characterized to assess (i) the Multi Locus Sequence Type (MLST), (ii) the presence of antimicrobial resistance genes (AMR), (iii) the presence of virulence genes coupled with Mobile Genetic Elements.

Results: MLST identified the strain as ST837. A plasmid of 60'691 bp, very similar to MW574937 plasmid of Escherichia coli was identified and carried the following AMR genes: aac(6')-II,bla_BEL-1, bla_IMP-19, msr(E), mph(E), sul1. This plasmid harboured several tra gene (traB, traC, traD, traG, traI, traJ, traKtraL, traM) of the transfer operon of E. coli conjugative F plasmid. Other AMR genes were located in the chromosome (bla_CMH-3 and fosA) or in other plasmids (bla_SHV-12 and mcr-4.3). In vitro the strain showed resistance to many beta-lactams, including cefiderocol, whereas, despite the presence of mcr-4.3 gene, it was susceptible to colistin.

Conclusions: Further studies are needed to better evaluate the origin of this strain, monitoring the presence of gram-negative bacilli with a similar molecular structure in our area.