Microbiological and clinical characteristics of bacteraemia caused by the hypermucoviscosity phenotype ofKlebsiella pneumoniaein Korea

Abstract

Hypermucoviscous (HV) isolates of Klebsiella pneumoniae have been linked to virulence potential in experimental infections. We examined 33 isolates of K. pneumoniae from patients with bacteraemia for the HV phenotype on agar culture, and determined their virulence potential by screening for capsular (K) serotype by polymerase chain reaction and the presence of seven virulence factor genes. Fourteen (42·4%) isolates expressed the HV phenotype and 11 of these were serotype K1 or K2; these serotypes were not identified in HV-negative isolates. The genes rmpA, rmpA2, aerobactin, wabG and allS were significantly more frequent in HV than non-HV isolates. Multilocus sequence typing identified 21 sequence types (ST), eight of which were found in HV-positive isolates and the clonal relatedness of isolates of the most frequent types (ST23 and ST11) from different hospitals was confirmed by pulsed-field gel electrophoresis. The HV phenotype was more associated with community-acquired infection with a lower frequency of fatal underlying illness, but with significantly more focal infections, notably liver abscesses. Clinicians should be aware of such clinical impacts of the HV phenotype.

Microbiological characteristics of hypermucoviscous Klebsiella pneumoniae isolates from different body fluids

“…We identified hvKP more frequently in urine and abscess, and less frequently in blood, tracheal secretion, and bile than another similar large hospital in China [26]. Most community-acquired infections were blood infections or a presence of different abscess, similar to previous reports [12,16,27]. Out of all, 40% (6/15) hvKP infections in nonblood/abscess group were defined as hospital-acquired versus 11.1% (1/9) in blood/abscess group.…”

Klebsiella pneumoniae: Going on the Offense with a Strong Defense

“…It has important roles in protecting against complement, including preventing C1q binding to bacteria, which inhibits subsequent activation of the complement pathway, as well as binding C3b away from the outer bacterial membrane and, thus, abrogating bacterial lysis by the complement membrane attack complex. jority of reports stating that wabG is harbored by 88 to 100% of K. pneumoniae isolates, although one report found wabG in only 5.3% of isolates (268,(270)(271)(272)(273)(274). K. pneumoniae strains lacking this gene are unable to generate the LPS outer core or to retain capsular antigen and are attenuated in intraperitoneal, pneumonic, and UTI rodent models of infection (275).…”

“…Kfu is an ABC iron transport system that is involved in the acquisition of iron by K. pneumoniae, and there is a strong association between the expression of this factor and HV K. pneumoniae strains (89,274,319). The relevance of this gene to virulence in vivo was established in a lethal mouse model of peritonitis with an HV K. pneumoniae deletion strain, where an isogenic kfu deletion mutant failed to cause mortality (319).…”

Aerobactin Mediates Virulence and Accounts for Increased Siderophore Production under Iron-Limiting Conditions by Hypervirulent (Hypermucoviscous) Klebsiella pneumoniae

“…Gene clusters for the Yersinia high-pathogenicity island (encodes yersiniabactin) and iucABCD-iutA (encodes aerobactin and its cognate receptor) were more prevalent in hvKP (38/42 and 39/42 strains, respectively) than in cKP (7/32 and 6/32, respectively) (25). In addition, aerobactin genes and aerobactin production, as demonstrated by a cross-feeding assay, were more common in hvKP strains than in cKP strains (8,15).…”

“…This pathogen is undergoing global dissemination from the Asian Pacific Rim, where it was first recognized in 1986 (3). In contrast to the usual health care-associated venue for "classical" K. pneumoniae (cKP) infections in the West, which have received increased notoriety due to their propensity for acquiring antimicrobial resistance determinants (4,5), hvKP causes serious, life-threatening infections in younger, healthy individuals in the community setting (6)(7)(8). Due to a lack of awareness and of an objective diagnostic test to differentiate hvKP from cKP, the incidence and full spectrum of disease are still being defined.…”