Characterization of Antibiotic Resistance Genes in Clinical Isolates of Pseudomonas aeruginosa from Hospital-Acquired Infections and Assessment of Efflux Pump Inhibitors on Restoring Antibiotic Susceptibility

Project Abstract

Characterization of Antibiotic Resistance Genes in Clinical Isolates of Pseudomonas aeruginosa from Hospital-Acquired Infections and Assessment of Efflux Pump Inhibitors on Restoring Antibiotic Susceptibility investigates the molecular and pharmacodynamic mechanisms underpinning multidrug resistance in P. aeruginosa strains isolated from hospital-acquired infections, with a focus on efflux pump systems and their inhibitors as a strategy to restore antibiotic effectiveness. The study employs a cross-sectional collection of 120 clinical isolates obtained from diverse departments of a tertiary care hospital over a 12-month period, ensuring representation of high-risk infection sites such as bloodstream, respiratory tract, wound, and urinary tract infections. Comprehensive phenotypic antimicrobial susceptibility testing using broth microdilution per CLSI guidelines establishes resistance profiles against a panel of frontline and limited-use antibiotics, including beta-lactams (piperacillin-tazobactam, ceftazidime, imipenem), aminoglycosides (gentamicin, amikacin), fluoroquinolones (ciprofloxacin), and polymyxins. Genotypic analyses employing PCR and whole-genome sequencing identify the distribution of key resistance determinants, including beta-lactamase genes (ESBL and AmpC variants), carbapenemase genes (VIM, IMP, NDM, KPC), aminoglycoside-modifying enzymes, and efflux pump operons (mexAB-OprM, mexCD-OprJ, mexEF-OprN), as well as mutations in oprD and regulatory genes that modulate porin expression and efflux activity. Quantitative real-time PCR evaluates the baseline expression levels of major efflux systems in both multidrug-resistant and susceptible isolates, establishing correlations between overexpression and resistance phenotypes. A subset of isolates undergoes transcriptomic profiling under antibiotic exposure to capture dynamic regulatory responses and identify compensatory pathways. The study then assesses the impact of specific efflux pump inhibitors (EPIs) such as PA?N and phenyl-arginine-?-naphthylamide, alone and in combination with antibiotics, on minimum inhibitory concentrations and time-kill dynamics, across multiple resistance backgrounds. Mechanistic insights are probed through accumulation assays using fluorescent substrates to quantify intracellular antibiotic retention and efflux activity, complemented by biofilm formation analyses to determine whether biofilm-associated resistance modulates EPI efficacy. Data integration employs multivariate statistical models to discern the relative contribution of intrinsic porin loss, enzymatic degradation, target modification, and efflux overexpression to the observed resistance patterns. Safeguards against potential confounders, including clonal relatedness and sample contamination, are implemented via MLST typing and rigorous quality controls. The study aims to (i) map the prevalence and diversity of antibiotic resistance genes in clinically significant P. aeruginosa isolates, (ii) delineate the role of efflux pumps in mediating multidrug resistance in this cohort, and (iii) evaluate the feasibility of EPIs to restore the activity of existing antibiotics, thereby guiding optimized combination therapies. Expected outcomes include a translational framework for integrating molecular resistance profiling with therapeutic decision-making, identification of high-risk resistance determinants for targeted surveillance, and evidence-based recommendations for incorporating efflux modulation into stewardship programs to curb hospital-acquired P. aeruginosa infections.

Project Overview

What This Project Is About

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A straightforward study of how certain bacteria from hospital infections carry genes that make them resistant to common antibiotics, and how blocking a specific bacterial mechanism (efflux pumps) can help antibiotics work again.

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The Problem It Addresses

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Hospitals see bacteria that steal resistance genes, making drugs less effective. This project looks at which genes are present in Pseudomonas aeruginosa and whether stopping efflux pumps can restore antibiotic power, addressing a key challenge in treating tough infections.

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Objectives of the Project

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1. Identify the common antibiotic resistance genes in clinical isolates of P. aeruginosa.
2. Assess how well efflux pump inhibitors reduce resistance in these bacteria.
3. Compare antibiotic susceptibility before and after inhibitor treatment.
4. Explain which antibiotics remain effective and under what conditions.
5. Discuss potential implications for hospital infection control and therapy.

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What You Will Do Step by Step

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Collect bacterial samples from hospital infections; test initial antibiotic response; screen for resistance genes using simple molecular tests; apply efflux pump inhibitors and re-test antibiotic susceptibility; analyze results to see if inhibitors improve effectiveness; summarize findings and limitations.

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Expected Outcome

Expect to identify key resistance genes and demonstrate whether efflux pump inhibitors can restore antibiotic activity in several antibiotics, informing treatment options and future research directions.