Clinical and phenotypic differences between classic and hypervirulent Klebsiella pneumonia: an emerging and under-recognized pathogenic variant

• Published in: European journal of clinical microbiology & infectious diseases 2012-06, Vol.31 (6), p.981-989
• Main Authors: Pomakova, D. K., Hsiao, C-B., Beanan, J. M., Olson, R., MacDonald, U., Keynan, Y., Russo, T. A.
• Format: Article
• Language: English
• Subjects: Abscesses; Animal models; Animals; Bactericidal activity; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Blood; Communicable Diseases, Emerging - epidemiology; Communicable Diseases, Emerging - microbiology; Communicable Diseases, Emerging - pathology; Community-Acquired Infections - epidemiology; Community-Acquired Infections - microbiology; Community-Acquired Infections - pathology; Disease Models, Animal; Drug resistance; Epidemiology; Genotype & phenotype; Humans; Infection; Infectious diseases; Internal Medicine; Klebsiella; Klebsiella Infections - epidemiology; Klebsiella Infections - microbiology; Klebsiella Infections - pathology; Klebsiella pneumoniae - classification; Klebsiella pneumoniae - isolation & purification; Klebsiella pneumoniae - pathogenicity; Liver; Liver Abscess - epidemiology; Liver Abscess - microbiology; Liver Abscess - pathology; Long term health care; Male; Medical Microbiology; Medical sciences; Metastases; Metastasis; Nosocomial infections; Pathogens; Pneumology; Pneumonia; Rats; Rats, Long-Evans; Respiratory system : syndromes and miscellaneous diseases; Spleen; Spleen - microbiology; Spleen - pathology; Virulence; Young Adult
• ISSN: 0934-9723; 1435-4373
• DOI: 10.1007/s10096-011-1396-6

The purpose of this study was to increase awareness, gain insight into acquisition, and assess the virulence of the hypervirulent (hypermucoviscous) clinical variant (hvKP) that is entrenched in the Pacific Rim but emerging in Western countries. A case of community-acquired liver abscess with metastatic spread to the spleen is described. Comparative in vitro and in vivo virulence studies on this isolate (hvKP1) and four randomly chosen blood isolates of “classic” K. pneumonia strains (cKP1-4) were performed. Cases of hvKP infection are occurring in Western countries and are under-recognized. A hypermucoviscous phenotype is a surrogate laboratory marker for this variant. The propensity of hvKP strains for metastatic spread in non-compromised hosts is both a defining and unusual trait. The mode of acquisition in the described case was unclear but potential means are discussed. hvKP1 was more resistant to complement and neutrophil-mediated bactericidal activity and was more virulent in a rat subcutaneous abscess model than cKP1-4. Recognition of the hypermucoviscous phenotype, defined by a positive “string-test”, will alert the microbiologist or clinician that the infecting strain may be a hvKP, which is hypervirulent compared to cKP. This will improve our understanding of the epidemiology and clinical spectrum of infection, which may be more extensive than appreciated.