Project description:Background: Enterobacter cloacae complex (ECC) is a common opportunistic pathogen and is responsible for causing various infections in humans. Owing to its inducible chromosomal AmpC β-lactamase (AmpC), ECC is inherently resistant to the 1st- and 2nd- generation cephalosporins. However, whether β-lactams antibiotics enhance ECC resistance remains unclear. Results: In this study, we found that subinhibitory concentrations (SICs) of cefazolin (CFZ) and imipenem (IMP) can advance the expression of AmpC and enhance its resistance towards β-lactams through NagZ in Enterobacter cloacae (EC). Further, AmpC manifested a substantial upregulation in EC in response to SICs of CFZ and IMP. In nagZ knockout EC (ΔnagZ), the resistance to β-lactam antibiotics was rather weakened and the effect of CFZ and IMP on AmpC induction was completely abrogated. NagZ ectopic expression can rescue the induction effects of CFZ and IMP on AmpC and increase ΔnagZ resistance. More importantly, CFZ and IMP have the potential to induce the expression of AmpR's target genes in a NagZ-dependent manner. Conclusions: Our findings suggest that NagZ is a critical determinant for CFZ and IMP to promote AmpC expression and resistance and that CFZ and IMP should be used with caution since they may aggravate ECC resistance. At the same time, this study further improves our understanding of resistance mechanisms in ECC.
Project description:While ESBL and AmpC beta-lactamases barely degrade carbapenems, they are able to bind them and prevent them from interacting with penicillin binding proteins thereby preventing their effect. When these beta-lactamases are expressed at a high level and combined with a decreased influx of carbapenems due to a decrease in membrane permeability, Enterobacterales can become resistant to carbapenems. In this study we developed a LC-MS/MS assay for the detection of the E. coli porins OmpC and OmpF, it’s chromosomal AmpC beta-lactamase and the plasmid-mediated CMY-2 beta-lactamase. Subsequently, we cultured CMY-2 positive E. coli isolates in the presence of meropenem and analyzed mutants that showed increased resistance to meropenem using our developed assay and western blot. In all five selected strains, a decrease in OmpC and/or OmpF was the first event towards an increase in meropenem minimum inhibitory concentrations (MICs). Subsequently, in four of the five isolate series, MICs increased further after an increase in CMY-2-like production.
Project description:The present study examines changes in global gene expression patterns and in virulence factor-associated genes in an extended spectrum beta-lactamase (ESBL)-producing UPEC (ESBL019) during the morphologic transitions induced by an ineffective antibiotic and in the presence of human primary bladder epithelial cells. The morphological shifts induced by ineffective antibiotics are associated with significant transcriptional virulence alterations in ESBL-producing UPEC, which may affect survival and persistence in the urinary tract.
