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Bacterial killing in vitro by abscess-derived neutrophils
J J Finlay-Jones1, P H Hart, L K Spencer
1Department of Clinical Microbiology, School of Medicine, Flinders University of South Australia, Adelaide.
Journal of Medical Microbiology
|February 1, 1991
Summary
Neutrophils in abscesses struggle to kill bacteria, even though they normally can. This impaired bacterial killing by neutrophils in intra-abdominal abscesses suggests a localized immune dysfunction.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Bacteria like Bacteroides fragilis, Escherichia coli, and Proteus mirabilis can persist in intra-abdominal abscesses despite the presence of neutrophils.
- Neutrophils isolated from abscesses exhibit impaired ability to kill phagocytosed bacteria in vitro compared to their in vitro activity against freshly added bacteria.
Purpose of the Study:
- To investigate the mechanisms behind the reduced bactericidal activity of neutrophils within intra-abdominal abscesses.
- To compare the in vitro killing of bacteria by neutrophils, considering whether bacteria were phagocytosed in vivo (within the abscess) or in vitro.
Main Methods:
- Induction of intra-abdominal abscesses in animal models using specific bacterial species (B. fragilis, E. coli, P. mirabilis, Staphylococcus aureus) and bran.
- Collection of neutrophils from induced abscesses.
- Assessment of in vitro bactericidal activity of these neutrophils against phagocytosed bacteria (in vivo) and bacteria added directly to the assay (in vitro).
Main Results:
- Killing of Escherichia coli and Proteus mirabilis by neutrophils was significantly reduced when bacteria were engulfed within the abscess compared to in vitro addition.
- Staphylococcus aureus killing by neutrophils was similar whether engulfed in vivo or in vitro.
- Despite reduced killing of Gram-negative bacteria within abscesses, S. aureus showed similar killing efficacy in both in vivo and in vitro phagocytosis scenarios.
Conclusions:
- Neutrophils within intra-abdominal abscesses exhibit impaired bactericidal function against certain bacteria, particularly Gram-negative species.
- The microenvironment of the abscess may contribute to neutrophil dysfunction, affecting their ability to clear infections.
- Further research is needed to elucidate the specific factors within the abscess that lead to this immune suppression.