Biofilm, virulence, and ESBL-mediated resistance: unmasking Klebsiella spp. UTIs

Klebsiella spp. has emerged as the second leading cause of urinary tract infection and a major cause of multidrug resistance. This study investigated the prevalence of genetic determinants related to infection and drug resistance, and the effects of biofilm on drug resistance from urinary tract infection (UTI) patients. A total of 718 clean voided midstream urine samples were collected from different age group patients at Mymensingh Medical College Hospital. Bacterial isolates were initially identified by cultural and biochemical assays, and finally confirmed by rcsA and pheX gene-based polymerase chain reaction (PCR). Antimicrobial susceptibility testing was performed by the disc diffusion method. The presence of virulence, extended-spectrum beta-lactamase (ESBL), and carbapenemase genes was determined by PCR. Biofilm formation was assessed using Congo red agar and microtiter plate assays. Among culture-positive isolates, 22 were confirmed as Klebsiella spp. (20 K. pneumoniae, 2 K. oxytoca), with 77.3% from females. The fimH, mrkD, and uge were the most prevalent virulence genes. Ninety-five percent of isolates were found to be multidrug resistant (MDR), and three were extremely drug resistant (XDR). ESBL genes bla_SHV (50%) and bla_TEM (40%) predominated, while bla_NDM (20%) and bla_OXA-48 (10%) were the main carbapenemase genes. Moderate (n = 6; 27.3%) to strong (n = 4; 18.1%) biofilm producers showed significantly higher resistance (P < 0.05). Regression analysis identified mrkD, uge, and allS as independent predictors of biofilm formation. The high prevalence of MDR K. pneumoniae with virulence and ESBL-carbapenemase genes highlights an alarming threat to UTI management in Bangladesh.

Klebsiella spp., particularly K. pneumoniae and K. oxytoca, are emerging as the second major uropathogens increasingly resistant to multiple antibiotics, complicating treatment and driving recurrent urinary tract infections. Their virulence factors, especially adhesins and biofilm formation, not only enhance colonization but also promote the spread of resistance genes, including extended-spectrum beta-lactamases (ESBLs) and carbapenemases. Despite their clinical significance, data on the molecular determinants of virulence and resistance in uropathogenic Klebsiella from Bangladesh remain limited. This study combines molecular and phenotypic approaches to characterize virulence genes, biofilm-forming potential, and antimicrobial susceptibility patterns of clinical isolates. By identifying key predictors of biofilm-associated multidrug resistance, the findings provide critical insights for guiding empirical therapy, informing infection control, and supporting antimicrobial stewardship. Ultimately, this work contributes to addressing the dual threat of virulence and drug resistance in urinary tract infection (UTI) management.