Characterization of antimicrobial resistance and virulence gene profiles in clinical Enterococcus isolates from a tertiary care hospital using whole-genome sequencing

Project Abstract

This study investigates the antimicrobial resistance patterns and virulence gene profiles of Enterococcus isolates obtained from clinical specimens in a tertiary care hospital, employing whole-genome sequencing (WGS) to elucidate the genomic determinants underpinning resistance and pathogenicity. A total of 150 Enterococcus isolates, comprising predominantly Enterococcus faecalis and Enterococcus faecium, were collected over a 24-month period from bloodstream, urinary tract, wound, and respiratory specimens. Conventional phenotypic antimicrobial susceptibility testing was complemented by WGS-based resistome analysis to identify both canonical and novel resistance determinants, including van genes (vanA, vanB), high-level aminoglycoside resistance markers (aac(6')-Ie-aph(2'')-Ia), macrolide-lincosamide-streptogramin (MLSB) resistance genes (ermB, msrC), tetracycline resistance determinants (tetM, tetL), and fluoroquinolone resistance mutations in gyrA and parC. Virulence profiling encompassed genes associated with adhesion, biofilm formation, cytolysin, gelatinase, aggregation substance, and surface-associated proteins (efaA, asa1, esp, hyl, gelE, cyl operon). Phylogenomic analyses and multilocus sequence typing (MLST) were conducted to discern clonal relationships and potential nosocomial transmission dynamics. The integration of genomic and phenotypic data revealed a high concordance between genotypic resistance determinants and observed resistance phenotypes for most antibiotic classes, while discrepancies highlighted potential regulatory or gene expression factors influencing resistance expression. Enterococcus faecium, particularly sequence types ST17 and ST80, emerged as the dominant hospital-adapted clones, exhibiting a broader resistome, including vanA-mediated vancomycin resistance, and a richer repertoire of virulence determinants compared to E. faecalis isolates. Notably, mobile genetic elements such as plasmids and transposons carrying resistance and virulence genes facilitated intra- and interspecies transfer, underscoring the potential for rapid dissemination within the clinical setting. Bioinformatic network analyses identified co-occurring resistance and virulence gene clusters, suggesting coordinated regulatory mechanisms that may enhance survival under antimicrobial pressure and host immune responses. Subgroup analyses demonstrated that isolates from bloodstream infections possessed a higher burden of virulence determinants and were more likely to harbor multi-resistance profiles relative to urinary or wound isolates, implicating systemic invasion as a function of combined genomic traits. The study also assessed the utility of WGS in surveillance by comparing turnaround times, cost implications, and data yield against traditional methods, concluding that WGS provides superior resolution for outbreak detection and resistance monitoring, albeit with considerations for data interpretation and infrastructure needs. The findings contribute to understanding the genomic architecture of Enterococcus in a tertiary care hospital, informing antimicrobial stewardship, infection control strategies, and the development of diagnostic assays that rapidly detect high-risk clones and virulence-associated determinants. Potential limitations include sampling bias, retrospective design, and gaps between genotype and expressed phenotype under various clinical conditions, which warrant prospective, multicenter validation to generalize the observed associations and to refine predictive models for resistance and virulence in Enterococcus populations.

Project Overview

What This Project Is About

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The project looks at how some bacteria called Enterococcus behave in a hospital setting, focusing on two main things: antimicrobial resistance (why they are hard to kill with medicines) and virulence genes (the traits that help them cause disease). It uses whole-genome sequencing, a modern method that reads the entire genetic material of the bacteria, to identify resistance and virulence factors.

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The Problem It Addresses

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Hospitals see infections caused by Enterococcus that are hard to treat because they resist common antibiotics and can become more harmful. Understanding which genes drive resistance and virulence helps track outbreak sources, tailor treatments, and inform infection control measures to protect patients.

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Objectives of the Project

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1. Identify common antimicrobial resistance genes in Enterococcus isolates from the hospital.
2. Identify key virulence gene profiles that may contribute to disease severity.
3. Determine how resistance and virulence genes correlate with clinical data (e.g., infection type, patient outcomes).
4. Explore genetic relationships among isolates to infer possible transmission events.
5. Provide a basic framework for routine genomic surveillance in the hospital setting.

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What You Will Do Step by Step

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1. Collect clinical Enterococcus isolates and associated patient data (de-identified).
2. Extract DNA and perform whole-genome sequencing.
3. Assemble genomes and identify resistance and virulence genes using online databases.
4. Analyze genetic relatedness to detect clusters or possible transmissions.
5. Summarize findings in relation to clinical outcomes and infection control records.
6. Discuss limitations and propose practical recommendations for the hospital.

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Expected Outcome

Expected outcomes include a clear map of resistance and virulence gene patterns in hospital Enterococcus isolates, insights into transmission links, and actionable suggestions for antibiotic stewardship and infection prevention.