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[Increase of resistance to Pseudomonas aeruginosa infection in mice caused by Staphylococcus aureus]
Abstract:
In our study of opportunistic pathogens, we have some indication that Staphylococcus aureus can increase resistance in mice against Pseudomonas aeruginosa. Intraperitoneal injections of sublethal doses of S. aureus had a protective effect in mice against lethal doses of P. aeruginosa, more so if living and coagulase-positive S. aureus strains were injected. This protective effect was obtained both with laboratory and freshly isolated hospital strains. The interval between these infections can be extended from 2 h up to 1 week and it is still possible to observe the resistance phenomenon. The increased resistance was accompanied by a decrease in viable units of P. aeruginosa in the peritoneal cavity of mice 6 h after the injection of this species. There was no protection by S. aureus against Candida albicans in similar experimental conditions. These observations indicate that intermicrobial ecology, understood here as the previous presence of another species in a host, may be a significant factor in the resistance to infection with opportunistic pathogens such as P. aeruginosa.
Insights
Staphylococcus aureus pre-infection enhances mouse resistance to Pseudomonas aeruginosa. This protective effect, observed even a week later, involves reduced P. aeruginosa levels, highlighting intermicrobial ecology in fighting opportunistic pathogens.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Opportunistic pathogens like Pseudomonas aeruginosa pose significant infection risks.
- Understanding host-pathogen interactions is crucial for developing new therapeutic strategies.
- The role of prior microbial colonization in modulating infection resistance is an emerging area of research.
Purpose of the Study:
- To investigate the potential protective effect of Staphylococcus aureus against Pseudomonas aeruginosa infection in a murine model.
- To explore the influence of S. aureus strain viability and coagulase positivity on this protective effect.
- To determine the duration of this protective phenomenon and its impact on pathogen load.
Main Methods:
- Mice were challenged with sublethal doses of Staphylococcus aureus (S. aureus) via intraperitoneal injection.
- Following a defined interval, mice were challenged with lethal doses of Pseudomonas aeruginosa (P. aeruginosa).
- Bacterial counts of P. aeruginosa in the peritoneal cavity were assessed at specific time points.
Main Results:
- Pre-administration of sublethal S. aureus doses conferred significant protection against lethal P. aeruginosa challenge in mice.
- Living, coagulase-positive S. aureus strains demonstrated a more pronounced protective effect.
- Protection was observed even when the interval between S. aureus and P. aeruginosa injections extended up to one week.
- A significant reduction in viable P. aeruginosa units was noted in the peritoneal cavity 6 hours post-infection in pre-treated mice.
- No protective effect was observed against Candida albicans, indicating specificity.
Conclusions:
- Prior colonization with Staphylococcus aureus can induce a state of resistance against subsequent Pseudomonas aeruginosa infection in mice.
- This phenomenon, termed intermicrobial ecology, suggests that the host's existing microbial environment plays a critical role in defense against opportunistic pathogens.
- The findings open avenues for exploring microbial-based strategies to enhance host resistance to specific bacterial infections.