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Effect of chemotactins released by Staphylococcus aureus and Pseudomonas aeruginosa on the murine respiratory tract
Abstract:
Staphylococcus aureus, the Pseudomonas aeruginosa temperature-sensitive (ts) mutant A/10/25, and the P. aeruginosa parental wild type were aerosolized to C5-deficient mice, and the total number of polymorphonuclear leukocytes (PMN) recovered by lung lavage was determined 4 h after aerosol exposure. S. aureus induced a slight but significant recruitment of PMN, as compared with the effect of a saline aerosol. Both wild-type P. aeruginosa and the ts mutant induced a significant PMN recruitment of a magnitude ca. 180 times higher than that produced by S. aureus. Gentamicin-killed ts P. aeruginosa induced a PMN recruitment of a magnitude similar to that produced by live ts P. aeruginosa. Thorough washing of the bacteria, however, removed ca. 90% of the chemotactic activity. Exposure of the animals to a ts P. aeruginosa culture supernatant aerosol induced significant PMN recruitment into the lower airways. The same culture supernatants were chemotactic for mouse PMN in a dose-dependent fashion when tested in vitro in the absence of serum. Culture supernatants of S. aureus exhibited weak chemotactic activity in vitro and did not induce PMN recruitment in the lungs when aerosolized to DBA/2J mice. The results suggest that chemotactins released by P. aeruginosa may be an important virulence factor and play a significant role in lung tissue damage.
Insights
Pseudomonas aeruginosa, but not Staphylococcus aureus, triggers significant polymorphonuclear leukocyte (PMN) recruitment in mouse lungs. Released chemotactins from P. aeruginosa are key virulence factors contributing to lung inflammation and damage.
Area of Science:
- Immunology
- Microbiology
- Pulmonary Medicine
Background:
- Bacterial infections in the lungs trigger an immune response involving polymorphonuclear leukocytes (PMN).
- Understanding the specific mechanisms of bacterial-induced inflammation is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the differential ability of Staphylococcus aureus and Pseudomonas aeruginosa to induce PMN recruitment in the lungs.
- To identify the role of bacterial components, specifically chemotactins, in mediating this immune response.
Main Methods:
- Aerosolization of S. aureus, P. aeruginosa wild type, and a temperature-sensitive mutant into C5-deficient mice.
- Quantification of PMN in lung lavage fluid 4 hours post-exposure.
- In vitro chemotaxis assays using bacterial components and culture supernatants.
Main Results:
- P. aeruginosa (both wild type and mutant) induced significantly higher PMN recruitment compared to S. aureus.
- Killed P. aeruginosa also induced substantial PMN recruitment, suggesting soluble factors are involved.
- Washing bacteria removed most chemotactic activity, while culture supernatants induced dose-dependent PMN chemotaxis in vitro.
- S. aureus showed minimal chemotactic activity both in vitro and in vivo.
Conclusions:
- P. aeruginosa releases potent chemotactic factors that are critical for PMN recruitment in the lungs.
- These chemotactins are likely a significant virulence factor contributing to lung tissue damage during P. aeruginosa infections.