MOLECULAR CHARACTERIZATION OF ANTIMICROBIAL RESISTANCE AND VIRULENCE GENES IN MULTIDRUG-RESISTANT BACTERIAL PATHOGENS

Abstract

Background: Antimicrobial resistance (AMR) has emerged as a major global public health challenge, particularly due to the increasing prevalence of multidrug-resistant (MDR) bacterial pathogens that limit therapeutic options and contribute to prolonged infections and treatment failure. The acquisition of antimicrobial resistance determinants together with virulence-associated genes may enhance bacterial persistence, pathogenicity, and clinical severity. Molecular characterization of these determinants is therefore essential for understanding resistance patterns and identifying high-risk bacterial strains.

Aim: This study aimed to characterize the antimicrobial resistance profiles and molecular determinants of resistance and virulence among multidrug-resistant bacterial pathogens and to investigate the distribution and co-occurrence of clinically important antimicrobial resistance and virulence genes.

Methods: A total of 150 bacterial isolates were recovered from clinical specimens and identified using standard microbiological and biochemical methods, followed by molecular confirmation using polymerase chain reaction (PCR). Antimicrobial susceptibility testing was performed against commonly used antibiotics representing different antimicrobial classes. MDR isolates were subsequently screened for selected antimicrobial resistance genes, including blaTEM, blaSHV, blaCTX-M, mecA, vanA, and qnrS, and virulence-associated genes such as fimH, ompA, hlyA, toxA, and lukS-PV. The prevalence, distribution, and co-occurrence of resistance and virulence determinants were evaluated among the identified bacterial pathogens.

Results: Of the 150 bacterial isolates examined, approximately 96 isolates (64.0%) exhibited multidrug-resistant phenotypes. The highest resistance rates were observed against ampicillin (78.7%), amoxicillin-clavulanate (68.0%), ciprofloxacin (61.3%), and ceftriaxone (58.7%), whereas relatively lower resistance was observed against meropenem (18.0%). Molecular analysis demonstrated the presence of blaCTX-M in 48.7%, blaTEM in 42.0%, and blaSHV in 26.7% of isolates. The mecA gene was detected in approximately 22.0% of isolates, while qnrS and vanA were identified in 20.7% and 12.0%, respectively. Among virulence determinants, fimH (45.3%), ompA (34.7%), hlyA (26.0%), toxA (18.7%), and lukS-PV (14.7%) were detected. Approximately 37.3% of MDR isolates carried two or more resistance genes, while 29.3% harbored multiple virulence-associated genes. Co-occurrence of both resistance and virulence determinants was observed in approximately 32.0% of MDR isolates, suggesting a substantial molecular burden of pathogenicity and antimicrobial resistance.

Conclusion: The findings indicate a high prevalence of multidrug resistance and demonstrate the coexistence of clinically important antimicrobial resistance and virulence determinants among bacterial pathogens. The frequent detection of beta-lactamase-associated genes and multiple virulence factors highlights the potential for difficult-to-treat infections and enhanced pathogenicity. Molecular surveillance integrating antimicrobial susceptibility testing with resistance and virulence gene profiling may provide valuable information for infection-control strategies, antimicrobial stewardship, and early identification of high-risk bacterial strains.