Microbiological and clinical characteristics of hypervirulent <i>Klebsiella pneumoniae</i> isolated from patients in tertiary centers: a retrospective study

This cross-sectional, retrospective study aimed to investigate the prevalence of hypervirulent <i>Klebsiella pneumoniae</i> (hvKp), its virulence-associated genes, and the clinical manifestations of hvKp infections. HvKp was defined in this study as <i>K. pneumoniae</i> with a positive string test and harboring the serotype K1 or K2 gene. A total of 180 isolates from various clinical specimens were collected from four main hospitals in Kelantan. All isolates were examined for the hypermucoviscous phenotype using the string test, while the presence of capsular serotypes and other virulence genes (<i>rmpA, rmpA2, iucA, magA,</i> and <i>peg-344</i>) was determined by polymerase chain reaction (PCR). Patients' clinical data were collected and analyzed. String test-positive isolates (23.8%, <i>n</i> = 43) were identified as hypermucoviscous <i>K. pneumoniae</i> (hmKp). Capsular serotypes K1 and K2 were detected in 11.1% (<i>n</i> = 20) and 6.1% (<i>n</i> = 11) of isolates, respectively. The prevalence of hvKp was 9.4% (<i>n</i> = 17). All hvKp isolates were positive for <i>rmpA, rmpA2, iucA,</i> and <i>peg-344</i> genes, while all ten hvKp-K1 serotype isolates were positive for <i>magA</i>, the K1 serotype-specific gene. The associations between all corresponding virulence genes and serotypes K1 and K2 were statistically significant (<i>p</i> < 0.05). HvKp infections were more prevalent in men and individuals with hypertension. Pneumonia was the most common clinical diagnosis in hvKp-infected patients, with a mortality rate of 12%. The presence of all biomarkers (<i>rmpA, rmpA2, magA</i> (for K1 serotype), <i>iucA</i>, and <i>peg-344</i>) in hmKp, in combination with clinical manifestations, may serve as a reliable approach for hvKp diagnosis and epidemiological surveillance.