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Bacteraemia and seeding of capsulate Bacteroides spp. and anaerobic cocci

I Brook

    Journal of Medical Microbiology
    |February 1, 1987
    PubMed

    Insights

    Capsulation significantly enhances the virulence of Bacteroides species and anaerobic gram-positive cocci. Encapsulated bacteria are more likely to cause bacteremia and spread to organs in mice compared to non-encapsulated strains.

    Area of Science:

    • Microbiology
    • Infectious Diseases
    • Bacteriology

    Background:

    • Bacterial capsulation is a key virulence factor.
    • The role of capsulation in anaerobic bacteria pathogenicity requires further elucidation.

    Purpose of the Study:

    • To investigate the impact of capsulation on the ability of Bacteroides fragilis, Bacteroides asaccharolyticus, and anaerobic gram-positive cocci to induce bacteremia and organ seeding.
    • To compare the virulence of capsulate versus non-capsulate anaerobic strains in both single and mixed infections.

    Main Methods:

    • Subcutaneous injection of various anaerobic bacterial strains (capsulate and non-capsulate) into mice, alone or in combination with aerobic/facultative organisms.
    • Monitoring and isolation of bacteria from blood, spleen, liver, and kidneys of infected animals.

    Main Results:

    • Capsulate anaerobes were recovered significantly more frequently from blood and organs (spleen, liver, kidneys) than non-capsulate strains.
    • In single infections, capsulate organisms were recovered from 39% of animals, versus only 3% for non-capsulate strains.
    • Capsulate Bacteroides fragilis demonstrated prolonged presence and higher recovery rates in mixed infections and when coinfected with other organisms.

    Conclusions:

    • Bacterial capsulation is a critical determinant of virulence for Bacteroides spp. and anaerobic gram-positive cocci.
    • Capsulate strains exhibit increased capacity for causing bacteremia and disseminating to organs.
    • These findings highlight the importance of capsular polysaccharides in anaerobic bacterial pathogenesis.

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