Horizontally-acquired AmpC (FOX-4) in Pseudomonas aeruginosa
Ontology highlight
ABSTRACT: Emergence of resistance to novel β-lactam β-lactamase inhibitor combinations due to horizontally-acquired AmpC (FOX-4) in Pseudomonas aeruginosa
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:Mycobacterium abscessus (Mab) causes serious infections that often require over 18 months of antibiotic combination therapy. With β lactam antibiotics being safe, double β-lactam and β-lactam/β-lactamase inhibitor combinations are of interest for improving treatment of Mab infections and minimizing toxicity. However, a mechanistic approach for building these combinations is lacking since little is known about which penicillin-binding protein (PBP) target receptors are inactivated by different β-lactams in Mab. This project aimed to identify PBPs in Mab and study the binding affinities of each of these PBPs with β-lactam antibiotics. These first PBP occupancy patterns in Mab provide a mechanistic foundation for selecting and optimizing safe and effective combination therapies with β-lactams.
2020-11-24 | PXD022644 | Pride
Project description:Novel beta-lactam/beta-lactamase inhibitor combinations against Pseudomonas aeruginosa
Project description:The transcriptional regulator AmpR controls expression of the AmpC ß-lactamase in P. aeruginosa and other bacteria. Studies have demonstrated that in addition to regulating ampC expression, AmpR also regulates the expression of the sigma factor AlgT/U and the production of some quorum-sensing regulated virulence factors. In order to understand the ampR regulon, we compared the expression profiles of PAO1 and its isogenic ampR mutant, PAO∆ampR in the presence and absence of sub-MIC ß-lactam stress. The analysis demonstrates that the ampR regulon is much more extensive than previously thought, with the deletion of ampR affecting the expression of over 300 genes. Expression of an additional 207 genes are affected by AmpR when the cells are exposed to sub-MIC ß-lactam stress, indicating that the ampR regulon in P. aeruginosa is much more extensive than previously thought. An inframe deletion of ampR was generated in P. aeruginosa PAO1. The wild type and ampR mutant strains were grown to mid-log phase and subjected to sub-MIC ß-lactam exposure. Total RNA was isolated from 2-hour ß-lactam exposed and unexposed cells to monitor changes in gene expression arising due to loss of ampR in the presence and absence of ß-lactam exposure.
Project description:The transcriptional regulator AmpR controls expression of the AmpC ß-lactamase in P. aeruginosa and other bacteria. Studies have demonstrated that in addition to regulating ampC expression, AmpR also regulates the expression of the sigma factor AlgT/U and the production of some quorum-sensing regulated virulence factors. In order to understand the ampR regulon, we compared the expression profiles of PAO1 and its isogenic ampR mutant, PAO∆ampR in the presence and absence of sub-MIC ß-lactam stress. The analysis demonstrates that the ampR regulon is much more extensive than previously thought, with the deletion of ampR affecting the expression of over 300 genes. Expression of an additional 207 genes are affected by AmpR when the cells are exposed to sub-MIC ß-lactam stress, indicating that the ampR regulon in P. aeruginosa is much more extensive than previously thought.
Project description:The Wnt/β-catenin signaling pathway is a critical regulator of development and stem cell maintenance. Mounting evidence suggests that the context-specific outcome of Wnt signaling is determined by the collaborative action of multiple transcription factors, including members of the highly conserved forkhead box (FOX) protein family. The contribution of FOX transcription factors to Wnt signaling has not been investigated in a systemic manner. Here, by combining β-catenin reporter assays with Wnt pathway-focused qPCR arrays and proximity proteomics of selected FOX family members, we determine that most FOX proteins are involved in the regulation of Wnt pathway activity and the expression of Wnt ligands and target genes. We conclude that FOX proteins are common regulators of the Wnt/β-catenin pathway that may control the outcome of Wnt signaling in a tissue-specific manner.