Project description:Enterobacter cloacae is a Gram-negative nosocomial pathogen of the ESKAPE (Enterococcus, Staphylococcus, Klebsiella, Acinetobacter, Pseudomonas, and Enterobacter spp.) priority group with increasing multi-drug resistance via the acquisition of resistance plasmids. However, E. cloacae can also display forms of antibiotic refractoriness, such as heteroresistance and tolerance. Here, we report that E. cloacae displays transient heteroresistance to aminoglycosides, which is accompanied with the formation of small colony variants (SCVs) with increased minimum inhibitor concentration (MIC) of gentamicin and other aminoglycosides used in the clinic, but not other antibiotic classes. To explore the underlying mechanisms, we performed RNA sequencing of heteroresistant bacteria, which revealed global gene-expression changes and a signature of the CpxRA cell envelope stress response. Deletion of the cpxRA two-component system abrogated aminoglycoside heteroresistance and SCV formation, pointing to its indispensable role in these processes. The introduction of a constitutively active allele of cpxA led to high aminoglycoside MICs, consistent with cell envelope stress response driving these behaviours in E. cloacae. Cell envelope stress can be caused by environmental cues, including heavy metals. Indeed, bacterial exposure to copper increased gentamicin MIC in the wild-type, but not in the ΔcpxRA mutant. Moreover, copper exposure also elevated the gentamicin MICs of clinical isolates from bloodstream infections, suggesting that CpxRA- and copper-dependent aminoglycoside resistance is broadly conserved in E. cloacae strains. Altogether, we establish that E. cloacae relies on transcriptional reprogramming via the envelope stress response pathway for transient resistance to a major class of frontline antibiotic.
Project description:The exchange of mobile genomic islands (MGIs) between microorganisms is often mediated by phages. As a consequence, not only phage genes are transferred, but also genes that have no particular function in the phage's lysogenic cycle. If they provide benefits to the phage's host, such genes are referred to as ‘morons’. The present study was aimed at characterizing a set of Enterobacter cloacae, Klebsiella pneumoniae and Escherichia coli isolates with exceptional antibiotic resistance phenotypes from patients in a neonatal ward. Unexpectedly, these analyses unveiled the existence of a novel family of closely related MGIs in Enterobacteriaceae. The respective MGI from E. cloacae was named MIR17-GI. Importantly, our observations show that MIR17-GI-like MGIs harbor genes associated with high-level resistance to cephalosporins. Further, we show that MIR17-GI-like islands are associated with integrated P4-like prophages. This implicates phages in the spread of cephalosporin resistance amongst Enterobacteriaceae. The discovery of a novel family of MGIs spreading ‘cephalosporinase morons’ is of high clinical relevance, because high-level cephalosporin resistance has serious implications for the treatment of patients with Enterobacteriaceal infections.
Project description:Enterobacter bugandensis is one of species from the E. cloacae complex (ECC) that has been predominantly associated to neonatal sepsis. A major concern with E. bugandensis and ECC bacteria in general is the frequent appearance of multidrug resistant isolates including those resistant to last-resort antibiotics, such as polymyxins, for which these microbes are in the ESKAPE list of global threat pathogens. Here, we investigated polymyxin B (PmB) resistance and heteroresistance in E. bugandensis by transcriptomics and a gene deletion approach using two clinical isolates. Genes encoded in the CrrAB-regulated operon including crrC and kexD were highly upregulated in both strains in the presence of PmB. We show in one of these isolates that ∆crrC and ∆kexD mutants exhibited lower levels of PmB resistance and heteroresistance than the parental strain. Moreover, the heterologous expression of CrrC and KexD proteins increased PmB resistance in a sensitive E. ludwigii clinical isolate and in the Escherichia coli K12 strain W3110. We also showed that the efflux pump AcrAB and TolC contribute to PmB resistance and heteroresistance. Deletion of the regulatory genes phoPQ and crrAB cause reduced PmB resistance and heteroresistance, while deletion of pmrAB did not have any effect. Our results also reveal that the addition of L-Ara4N into the lipid A, mediated by the arnBCADTEF operon, is critical to determine PmB resistance, while the deletion of eptA, encoding a PEtN transferase had no effect. Finally, PmB resistance did not correlate with pathogenicity in the Galleria mellonella infection model.
2024-04-05 | PXD042287 | Pride
Project description:Genomic analysis of carbapenem-nonsusceptible Enterobacter cloacae
Project description:Recently, we have reported on a highly drug-resistant carbapenemase-producing isolate of Enterobacter cloacae (Nepal et al., Virulence. 2018; 9: 1377-1389). In the present study, we asked the question whether and, if so, how this isolate responds to a sub-inhibitory challenge with the antibiotic imipenem. To answer this question, we applied a SILAC proteomics approach that allowed the quantification of changes in the relative abundance of bacterial protein in response to imipenem. The results show that the investigated E. cloacae isolate mounts a highly specific response to counteract the detrimental effects of imipenem.
Project description:Oligonucleotide DNA microarrays were used as a platform to compare C. jejuni isolates from feedlot cattle and human clinical cases from Alberta. Comparative genomic hybridization (CGH) analysis was performed on 87 isolates (46 bovine, 41 human) obtained within the same geographical regions and time frame. In addition, We also performed gene association analysis to determine if any genes may be differentially distributed between human and cattle sources or between clusters dominated by either human or cattle isolates (“human enriched” vs “cattle enriched”). Keywords: Comparative Genomic Hybridization; Genomic epidemiology; Gene-association study
Project description:Comparative genomic analysis of the most important S. enterica sspI clinical isolates and respective strains from the SARB collection Keywords: other