Association Between Antibiotic Resistance, Biofilm Formation, and Virulence Gene Profiles in Clinical Isolates of Klebsiella pneumoniae

Klebsiella pneumoniae is a leading cause of healthcare-associated infections, increasingly characterized by multidrug resistance and enhanced virulence. This study aimed to investigate the interplay between antibiotic resistance, biofilm formation, and virulence gene profiles among clinical isolates of Klebsiella pneumoniae in Tehran, Iran. Clinically confirmed isolates were recovered from urine, wound, blood, catheter, and respiratory specimens. Antimicrobial susceptibility testing revealed alarming resistance rates: 100% to imipenem, ~80% to ampicillin and cefotaxime, and 69.23% were ESBL producers. Notably, a significant association was found between the hypervirulent Klebsiella pneumoniae (hvKp) phenotype and ESBL production (P = 0.003), indicating the emergence of convergent strains combining resistance and virulence. Phenotypic assays showed that 76% of isolates were capable of biofilm formation. Molecular analysis revealed high prevalence of key virulence genes: mrkA (53.84%), wzm (46.15%), pgaA (34.61%), and wbbM (23.07%). Strong positive correlations were observed between wbbM and both wzm (r = 0.734) and pgaA (r = 0.549), as well as between mrkA and wbbM (r = 0.458), suggesting synergistic roles in biofilm development. HVKp isolates were predominantly recovered from respiratory samples (66.66%), whereas classical Klebsiella pneumoniae (cKp) dominated urinary and bloodstream sources. These findings underscore a concerning convergence of carbapenem resistance, hypervirulence, and robust biofilm-forming capacity in clinical Klebsiella pneumoniae isolates in Iran. Such strains pose a serious therapeutic challenge and highlight the urgent need for enhanced surveillance, rapid diagnostics, and alternative treatment strategies targeting virulence and biofilm mechanisms.