Genomic Characterization of IMP-Producing Pseudomonas aeruginosa in Bulgaria Reveals the Emergence of IMP-100, a Novel Plasmid-Mediated Variant Coexisting with a Chromosomal VIM-4

Abstract

Multidrug-resistant (MDR) Pseudomonas aeruginosa infections represent a major public health concern and require comprehensive understanding of their genetic makeup. This study investigated the first occurrence of imipenemase (IMP)-carrying P. aeruginosa strains from Bulgaria. Whole genome sequencing identified a novel plasmid-mediated IMP-100 allele located in a a novel In4886 integron embedded in a putative Tn7700 transposon. Two other closely related chromosomal IMP variants, IMP-13 and IMP-84, were also detected. The IMP-producers were resistant to last-line drugs including cefiderocol (CFDC) (two out of three) and susceptible to colistin. The IMP-13/84 cassettes were situated in a In320 integron inserted in a Tn5051-like transposon as previously reported. Lastly, the p4782-IMP plasmid rendered the PA01 transformant resistant to CFDC, suggesting a transferable CFDC resistance. A variety of virulence factors associated with adhesion, antiphagocytosis, iron uptake, and quorum sensing, as well as secretion systems, toxins, and proteases, were confirmed, suggesting significant pathogenic potential consistent with the observed strong biofilm formation. The emergence of IMP-producing MDR P. aeruginosa is alarming as it remains unsusceptible even to last-generation drugs like CFDC. Newly detected IMP-100 was even located in a CFDC-resistant XDR strain.

Genomic Characterization of Carbapenemase-Producing Enterobacter hormaechei, Serratia marcescens, Citrobacter freundii, Providencia stuartii, and Morganella morganii Clinical Isolates from Bulgaria

“…Total genomic DNA for PCR and whole-genome sequencing was extracted using the PureLink™ Genomic DNA Mini Kit (Thermo Fisher Scientific, Missouri, TX, USA) following the manufacturer's instruction, except that all homogenization steps were performed by pipetting. Primer pairs from prior publications were used in a previously described multiplex PCR [30] to screen all isolates for class A, class B, and class D carbapenemases [31][32][33][34][35]. PCR conditions are detailed in Supplementary Table S5.…”