Cephem Potentiation by Inactivation of Nonessential Genes Involved in Cell Wall Biogenesis of β-Lactamase-Producing Escherichia coli

Abstract

Reversal of antimicrobial resistance is an appealing and largely unexplored strategy in drug discovery. The objective of this study was to identify potential targets for "helper" drugs reversing cephem resistance in Escherichia coli strains producing ␤-lactamases. A CMY-2-encoding plasmid was transferred by conjugation to seven isogenic deletion mutants exhibiting cephem hypersusceptibility. The effect of each mutation was evaluated by comparing the MICs in the wild type and the mutant harboring the same plasmid. Mutation of two genes encoding proteins involved in cell wall biosynthesis, dapF and mrcB, restored susceptibility to cefoxitin (FOX) and reduced the MICs of cefotaxime and ceftazidime, respectively, from the resistant to the intermediate category according to clinical breakpoints. The same mutants harboring a CTX-M-1-encoding plasmid fell into the intermediate or susceptible category for all three drugs. Individual deletion of dapF and mrcB in a clinical isolate of CTX-M-15-producing E. coli sequence type 131 (ST131) resulted in partial reversal of ceftazidime and cefepime resistance but did not reduce MICs below susceptibility breakpoints. Growth curve analysis indicated no fitness cost in a ΔmrcB mutant, whereas a ΔdapF mutant had a 3-fold longer lag phase than the wild type, suggesting that drugs targeting DapF may display antimicrobial activity, in addition to synergizing with selected cephems. DapF appeared to be a potential FOX helper drug target candidate, since dapF inactivation resulted in synergistic potentiation of FOX in the genetic backgrounds tested. The study showed that individual inactivation of two nonessential genes involved in cell wall biogenesis potentiates cephem activity according to drug-and strain-specific patterns.

Genotypic Detection and Characterization of Adhesins in Clinical Escherichia coli Isolates

“…They are very often responsible for causing disease in the host and converting non-pathogenic bacteria into dangerous pathogens [2]. In bacteria, virulence factors are often encoded on plasmids and chromosomes and can easily be spread through horizontal gene transfer [3].The virulence of the individual strains in a given infection is determined by the presence and the actual expression of the virulence genes which are present in them and also by the environmental conditions in the host [4].…”

Phenotypic detection of multidrug resistant extended-spectrum beta-lactamase (ESBL) producing Escherichia coli from clinical samples

“…Escherichia coli is one of the most important opportunistic Gram negative bacteria, resistant to many antimicrobial agents and cause different infections possession of many virulence genes encoding to some important virulence factors (Baker et al, 2017). It is a major human pathogen, causing up to 80% of uncomplicated UTI and 30% of bacteraemia cases (Ejikeugwu et al, 2012).…”

“…During the last couple of years increasing numbers of antibiotic-resistant bacteria have become a problem in the field of infection control. Pathogenic E. coli constitutes a significant threat to public health, and the emergence of extended-spectrum beta-lactamase (ESBL)-producing E. coli with high virulence potential is alarming (Umadevi et al, 2011;Chakraborty et al, 2012;Baker et al, 2017).…”

“…The problems which are associated with ESBLs include multidrug resistance, difficulty in detection and treatment, and increased mortality. Multidrug-resistant E. coli (MDR-ECO) strains have increased with the application of broad-spectrum antibiotics (Saeidi et al, 2014;Baker et al, 2017).…”

Hybrid Inhibitors of DNA Gyrase A and B: Design, Synthesis and Evaluation

“…To study the factors that influence the antibacterial activities of these compounds, the hybrids were also tested on E. coli BW25113 wild-type and mutant strains ( Table 3 ). The first three of the mutated genes for dapF , mrcB , and surA are involved in peptidoglycan biosynthesis and maturation of outer membrane proteins [ 31 ]; this leads to mutants with disturbed cell walls, which are thus more permeable. The other two mutants were for the acrB and tolC genes that encode efflux pump proteins [ 32 ].…”