Temporal Interplay between Efflux Pumps and Target Mutations in Development of Antibiotic Resistance in Escherichia coli

Abstract

The emergence of resistance presents a debilitating change in the management of infectious diseases. Currently, the temporal relationship and interplay between various mechanisms of drug resistance are not well understood. A thorough understanding of the resistance development process is needed to facilitate rational design of countermeasure strategies. Using an in vitro hollow-fiber infection model that simulates human drug treatment, we examined the appearance of efflux pump (acrAB) overexpression and target topoisomerase gene (gyrA and parC) mutations over time in the emergence of quinolone resistance in Escherichia coli. Drug-resistant isolates recovered early (24 h) had 2-to 8-fold elevation in the MIC due to acrAB overexpression, but no point mutations were noted. In contrast, high-level (>64؋ MIC) resistant isolates with target site mutations (gyrA S83L with or without parC E84K) were selected more readily after 120 h, and regression of acrAB overexpression was observed at 240 h. Using a similar dosing selection pressure, the emergence of levofloxacin resistance was delayed in a strain with acrAB deleted compared to the isogenic parent. The role of efflux pumps in bacterial resistance development may have been underappreciated. Our data revealed the interplay between two mechanisms of quinolone resistance and provided a new mechanistic framework in the development of high-level resistance. Early low-level levofloxacin resistance conferred by acrAB overexpression preceded and facilitated high-level resistance development mediated by target site mutation(s). If this interpretation is correct, then these findings represent a paradigm shift in the way quinolone resistance is thought to develop.

Quantitative Contributions of Target Alteration and Decreased Drug Accumulation to Pseudomonas aeruginosa Fluoroquinolone Resistance

“…In line with this, it has been demonstrated that deletion of efflux pumps significantly reduces the frequency of emergence of fluoroquinolone-resistant mutant isolates (46,52). A key to preventing fluoroquinolone resistance in P. aeruginosa may therefore be to strictly avoid the use of low doses of fluoroquinolones and thus to preclude the emergence of first-step mutations that confer resistance to fluoroquinolones.…”

“…Although these P. aeruginosa isolates are categorized as susceptible, it remains to be shown that it is safe to treat them with fluoroquinolones (49). The stepwise enrichment of fluoroquinolone resistance mutations has been described previously in several in vitro studies (50,51,52). Mutants at each step are enriched when drug concentrations fall within a specific range called the mutant selection window (1,53).…”

Molecular characterization of quinolone resistance mechanisms and extended-spectrum β-lactamase production in Escherichia coli isolated from dogs

“…When resistance was restricted to NAL, we have verified the presence of the PMQR gene qnrS or the presence of one mutation in the chromosomal genes; such genotypes seem insufficient to confer resistance to CIP. However, resistance may not only be determined by the presence of qnrS gene; other factors (not evaluated) such as the possible presence of efflux pumps or organic solvent tolerance may also be responsible for the resistance [37].…”

Does mutation in gyrA and/or parC or efflux pump expression play the main role in fluoroquinolone resistance in Escherichia coli urinary tract infections?: A statistical analysis study

“…In particular, the efflux pump is known to be related to resistance to aminoglycosides [18] and FQs [19]. Early low-level LVFX resistance is conferred by efflux pump AcrAB overexpression, followed by high-level resistance mediated by target site mutations [19].…”

“…Early low-level LVFX resistance is conferred by efflux pump AcrAB overexpression, followed by high-level resistance mediated by target site mutations [19]. The data in the current study revealed that QRDR mutations in gyrA and parC were more highly correlated with FQ MICs of E. coli for all tested FQs than the four efflux pump genes tested, considering their P-values, even though one of the efflux pump genes (marA) also showed a significant correlation with high MICs to the tested FQs.…”