Related Experiment Videos
Lethal microbial synergism in intra-abdominal infections. Escherichia coli and Bacteroides fragilis
Abstract:
The ability of Bacteroides fragilis and Escherichia coli to produce synergistic mortality when mixed into intraperitoneal (IP) fibrin clots was tested in rats. The addition of B fragilis (2 X 10(9) colony-forming units/clot) to E coli (2 X 10(8) colony-forming units/clot) in the clot significantly enhanced both early and late mortality rates when compared to either E coli or B fragilis alone. Multiple washings of B fragilis prior to mixing with E coli in the clot delayed the enhancement of lethality from 24 to 48 hours. By seven days, washed B fragilis was as synergistic with E coli as unwashed B fragilis plus E coli. Furthermore, unwashed killed B fragilis was as synergistic when mixed with E coli in the fibrin clot as unwashed living B fragilis. However, washed dead B fragilis plus E coli produced no greater mortality than E coli alone. The lethality of an IP clot containing E coli was significantly increased when B fragilis was mixed with it in the same clot, injected free IP, and or implanted into a separate IP clot. Intraperitoneal E coli-fibrin clot lethality was not increased by subcutaneous B fragilis and was only slightly enhanced by intravenous B fragilis inoculation. The strain of B fragilis used in these studies did not produce fibrinolysins at any concentration. The data support the idea that synergistic mortality between E coli and B fragilis in this model is caused by a heat-stable surface factor produced by B fragilis, which acts to increase the lethal effects of E coli.
Insights
Bacteroides fragilis enhances Escherichia coli lethality in rat fibrin clots via a heat-stable surface factor. This synergy increases mortality, indicating a key interaction in infection models.
Area of Science:
- Microbiology
- Infectious Diseases
- Pathogenesis
Background:
- Bacterial synergy can complicate infection outcomes.
- Understanding interactions between common gut bacteria like Bacteroides fragilis and Escherichia coli is crucial for infection research.
Purpose of the Study:
- To investigate the synergistic mortality between Bacteroides fragilis and Escherichia coli within an intraperitoneal fibrin clot model in rats.
- To identify the mechanism behind the observed synergistic lethality.
Main Methods:
- Rats were inoculated with fibrin clots containing combinations of Bacteroides fragilis and Escherichia coli.
- Bacterial viability, washing, and route of administration were manipulated to assess their impact on mortality.
- Mortality rates were compared between groups receiving single bacterial species, combined species, and varied administration methods.
Main Results:
- Bacteroides fragilis significantly enhanced the mortality caused by Escherichia coli in intraperitoneal fibrin clots.
- The synergistic effect was mediated by a heat-stable factor on the surface of Bacteroides fragilis, not by fibrinolysin production.
- The route of Bacteroides fragilis administration influenced the onset and degree of synergy.
Conclusions:
- A heat-stable surface factor from Bacteroides fragilis potentiates the lethal effects of Escherichia coli in this rat model.
- This interaction highlights the importance of bacterial surface components in polymicrobial infections.
- The findings provide insights into the pathogenesis of mixed bacterial infections.