Assessment of hypermucoviscosity as a virulence factor for experimental Klebsiella pneumoniaeinfections: comparative virulence analysis with hypermucoviscosity-negative strain

Abstract

BackgroundKlebsiella pneumoniae displaying the hypermucoviscosity (HV) phenotype are considered more virulent than HV-negative strains. Nevertheless, the emergence of tissue-abscesses-associated HV-negative isolates motivated us to re-evaluate the role of HV-phenotype.ResultsInstead of genetically manipulating the HV-phenotype of K. pneumoniae, we selected two clinically isolated K1 strains, 1112 (HV-positive) and 1084 (HV-negative), to avoid possible interference from defects in the capsule. These well-encapsulated strains with similar genetic backgrounds were used for comparative analysis of bacterial virulence in a pneumoniae or a liver abscess model generated in either naïve or diabetic mice. In the pneumonia model, the HV-positive strain 1112 proliferated to higher loads in the lungs and blood of naïve mice, but was less prone to disseminate into the blood of diabetic mice compared to the HV-negative strain 1084. In the liver abscess model, 1084 was as potent as 1112 in inducing liver abscesses in both the naïve and diabetic mice. The 1084-infected diabetic mice were more inclined to develop bacteremia and had a higher mortality rate than those infected by 1112. A mini-Tn5 mutant of 1112, isolated due to its loss of HV-phenotype, was avirulent to mice.ConclusionThese results indicate that the HV-phenotype is required for the virulence of the clinically isolated HV-positive strain 1112. The superior ability of the HV-negative stain 1084 over 1112 to cause bacteremia in diabetic mice suggests that factors other than the HV phenotype were required for the systemic dissemination of K. pneumoniae in an immunocompromised setting.

TREM-1 Promotes Survival during Klebsiella pneumoniae Liver Abscess in Mice

“…The oral infection model of KPLA was regarded as the most suitable animal model in the subsequent studies (33,46,47). Of note, a high dose of K. pneumoniae has to be used to establish the colonization and subsequent bacterial translocation in the mouse model (45).…”

Complete Genome Sequence of Klebsiella pneumoniae 1084, a Hypermucoviscosity-Negative K1 Clinical Strain

“…However, 1084 was as potent as 1112 in inducing liver abscesses and exhibited an ability superior to that of 1112 in causing bacteremia and mortality in diabetic mice. The advantageous tissueinvasive ability of 1084 indicates that the HV phenotype per se is not a determinant for K. pneumoniae virulence in a diabetic host (4). The naturally selected strain 1084, therefore, serves as an ideal model for identifying virulence factors, rather than reliance on the HV phenotype that contributes significantly to the pathogenesis of K. pneumoniae.…”

Extended-Spectrum-β-Lactamase-Producing Escherichia coli Isolate Possessing the Shiga Toxin Gene ( stx 1 ) Belonging to the O64 Serogroup Associated with Human Disease in India

“…As in the present study, a higher prevalence of the bla CTX-M-1 gene than of the bla SHV gene has been reported, which may be due to the wide use of extended-spectrum cephalosporins in India, especially ceftriaxone and cefotaxime, or it may be associated with the high mobilization of the encoding genes (21,22,23,24). In a conjugation study, neither of the plasmids carrying any one of the target genes could be transferred horizontally to the recipient isolates.…”