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Published on: January 7, 2019
Hypervirulent Klebsiella pneumoniae causing aortitis retains its capsule and mucoviscosity and remains genotypically
Thomas A Russo1, Ulrike Carlino-MacDonald1, Zachary J Drayer1
1University at Buffalo, State University of New York.
Abstract:
Aortitis due to hypervirulent Klebsiella pneumoniae (hvKp) in a Belarusian male from central New York is described. Isolates at the time of diagnosis (Kp031824-1, Kp031824-2) and after 12 weeks of antimicrobial therapy (Kp070124) were characterized. Kp070124 was genomically and phenotypically unchanged retaining its capsular polysaccharide and mucoviscosity. In vitro studies established that capsule minus derivatives of Kp031824-1 and Kp031824-2 can occur due to mutations in wcaJ. But this genotype/phenotype was not selected for in Kp070124 after ≥15 weeks in the systemic compartment. Compared to capsule minus derivatives, the capsule positive phenotype demonstrated resistance to phagocytosis, but not to complement mediated bactericidal activity, suggesting resistance to phagocytosis is a more important defense mechanism at this site of infection. These data also support that a capsule positive, mucoviscous phenotype is selected for during infections in the systemic compartment. The surprising result that capsule positive strains have increased sensitivity to complement mediated bactericidal activity compared to capsule minus strains requires further investigation. The duration of therapy for this syndrome remains unclear but should be prolonged; adjunctive therapies (e.g. phage therapy, passive immunization, augmentation of cell mediated bactericidal activity) may be needed to overcome the protection endowed by the mucoviscous capsule of hvKp.
Insights
Hypervirulent Klebsiella pneumoniae (hvKp) caused aortitis. hvKp maintained its protective capsule during therapy, suggesting prolonged treatment and adjunctive therapies are necessary for this infection.
Area of Science:
- Infectious Diseases
- Microbiology
- Pathogenesis
Background:
- Aortitis is a severe infection, and hypervirulent Klebsiella pneumoniae (hvKp) is an emerging pathogen.
- Understanding hvKp virulence factors is crucial for effective treatment strategies.
Purpose of the Study:
- To characterize hvKp isolates from a patient with aortitis.
- To investigate the role of capsular polysaccharide and mucoviscosity in hvKp pathogenesis and treatment response.
Main Methods:
- Genomic and phenotypic characterization of hvKp isolates before and after antimicrobial therapy.
- In vitro studies to assess the impact of capsule expression on bacterial survival and host immune responses.
Main Results:
- The hvKp isolate remained genomically and phenotypically unchanged, retaining its capsule and mucoviscosity after prolonged antimicrobial therapy.
- Capsule-positive phenotype conferred resistance to phagocytosis but not complement-mediated killing, suggesting phagocytosis resistance is key in systemic infections.
- Capsule-positive strains showed increased sensitivity to complement-mediated bactericidal activity compared to capsule-minus strains, warranting further investigation.
Conclusions:
- The mucoviscous capsule of hvKp is a critical virulence factor selected for in systemic infections.
- Prolonged antimicrobial therapy is likely required for hvKp aortitis.
- Adjunctive therapies may be necessary to overcome capsule-mediated protection and improve treatment outcomes.
