A Study of the virulence genes of hypermucoviscous Klebsiella pneumoniae and their comparison with classic Klebsiella pneumoniae

Abstract

Background. Klebsiella pneumoniae is an important opportunistic pathogen responsible for a wide range of healthcare- and community-associated infections. Hypermucoviscous K. pneumoniae exhibits enhanced virulence due to the presence of specific virulence-associated genes that contribute to bacterial pathogenicity and disease severity. Aim. To determine the prevalence of hypermucoviscous Klebsiella pneumoniae isolates and investigate the distribution of selected virulence genes (k2, kfu, entB, hcp, rmpA, and magA) in comparison with classical K. pneumoniae isolates. Methods. Fifty-seven clinical isolates were collected from different clinical specimens, including urine, blood, sputum, cerebrospinal fluid, tissue artificial bone, burns, and wound samples, from several hospitals in Baghdad between August and November 2024. Bacterial isolates were identified using microscopic examination, cultural characteristics, biochemical tests, and the Vitek-2 Compact system. Hypermucoviscosity was evaluated using the string test. Polymerase chain reaction (PCR) was performed to detect the presence of the virulence genes (k2, kfu, entB, hcp, rmpA, and magA), and statistical analysis was conducted using the Pearson Chi-square test. Results. Of the 57 collected isolates, 55 were confirmed as K. pneumoniae, with urinary tract infections representing the highest proportion (58.18%). Only five isolates (9%) exhibited the hypermucoviscous phenotype. PCR analysis of 35 representative isolates demonstrated that the entB gene was detected in 100% of isolates, followed by kfu and hcp genes (97.14% each), while the k2 gene was detected in 88.57% of isolates. Neither rmpA nor magA genes were detected in any isolate. Significant differences were observed in the distribution of virulence genes (p ≤ 0.005). Conclusion. The study demonstrated that both hypermucoviscous and classical K. pneumoniae isolates harbor multiple virulence genes, with entB being the most prevalent. The absence of rmpA and magA genes indicates that hypermucoviscosity is likely influenced by additional virulence determinants rather than these genes alone.