Hypervirulent Klebsiella pneumoniae (hv Kp): Overview, Epidemiology, and Laboratory Detection

Abstract

Klebsiella pneumoniae (Kp) is a Gram-negative pathogen responsible for both hospital- and community-acquired infections. Kp is classified into 2 distinct pathotypes: classical K. pneumoniae (cKp) and hypervirulent K. pneumoniae (hvKp). First described in Taiwan in 1986, hvKp are highly pathogenic and characterized by unique phenotypic and genotypic traits. The hypermucoviscous (hmv) phenotype, generally marked by overproduction of the capsule, is often associated with hvKp, although recent studies show that some cKp strains may also have this characteristic. Furthermore, hvKp can cause severe community-acquired infections in healthy people and have been associated with metastatic infections such as liver abscess, meningitis, and endophthalmitis. HvKp are increasingly being reported in hospital-acquired settings, complicating treatment strategies. In particular, while hvKp have historically been antibiotic-susceptible, multidrug-resistant (MDR) strains have emerged and pose a significant public health threat. The combination of high virulence and limited antibiotic options demands further research into virulence mechanisms and rapid identification methods. This review discusses the epidemiology of hvKp and their virulence factors, highlighting the importance of phenotypic and non-phenotypic tests, including next-generation molecular diagnostics, for the early detection of hvKp.

Keywords: ESBL; Klebsiella pneumoniae; WGS; carbapenemases; detection; epidemiology; hvKp; hypermucoviscous; in vivo; string test; virulence.

Figure 1.

String test on Columbia agar with 5% sheep blood (CSBA, Oxoid). Since a string with a length >5 mm was observed, the test result was considered positive (ie, hypermucoviscous phenotype of the K. pneumoniae strain).