The Correlation Between Capsular Serotypes and Some Virulence Factors of Classical and Hyper Virulent Klebsiella Pneumoniae Isolated from Urinary Tract Infections

Background: Klebsiella pneumoniae is a major pathogen in urinary tract infections (UTIs), with its virulence influenced by specific capsular serotypes and strain types. Objectives: This study aims to investigate the association between virulence factors and capsular serotypes in classical (cKp) and hypervirulent (hvKp) K. pneumoniae isolates from UTIs. Patients and Methods: A total of 280 urine samples were collected from patients at Medical City Hospital in Baghdad, Iraq, between November 2023 and May 2024. Polymerase chain reaction (PCR) was used for molecular identification and capsular serotyping. Virulence factors assessed included biofilm formation, hemolytic activity, serum resistance, and siderophore production. Results: Among 41 classical cKp, 19 were identified as serotypes K1 or K2, while the remaining 22 belonged to other serotypes. Of the 21 hypervirulent hvkp, 18 were associated with serotypes K1, K2, K20, or K54. All isolates exhibited biofilm formation with no significant difference between cKp and hvKp. However, hvKp strains demonstrated significantly higher hemolytic activity, particularly in K1 and K2 serotypes, although differences between K1 and K2 within hvKp were not statistically significant. Serum resistance was significantly greater in hvKp strains (p > 0.05), with K2 showing higher resistance than K1 in both groups. Siderophore production was also significantly elevated in hvKp, with K1 strains exhibiting the highest levels. Conclusion: Capsular serotyping may offer valuable insights for clinical diagnostics and therapeutic decision-making in UTIs caused by K. pneumoniae. Keywords: Capsular serotypes, Virulence factors, Klebsiella pneumoniae, Hypervirulent, UTI.