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Bactericidal activity of normal human serum against Morganella, Proteus, and Providencia strains
U Nawrot1, G Mokracka-Latajka, J Grzybek-Hryncewicz
1Department of Microbiology, Medical Academy, Wrocław, Poland.
Abstract:
The susceptibility od Proteus, Providencia, and Morganella strains to bactericidal action of human serum was examined. The percentage of survival was determined after one and three hours incubation with 50% human serum. The susceptible strains were treated by serum preparations with blocked classical or alternative complement activation pathways as well as with lysozyme removed. Following mechanisms of the bactericidal action of serum were found: complement activated by the classical or alternative pathway with participation of lysozyme, complement activated simultaneously via both pathways-while the participation of lysozyme was necessary for killing some strains and superfluos for others and complement activated only via the classical pathway without lysozyme.
Insights
Human serum effectively kills Proteus, Providencia, and Morganella bacteria. Its bactericidal action involves complement pathways and lysozyme, with varying mechanisms depending on the bacterial strain.
Area of Science:
- Microbiology
- Immunology
Background:
- Proteus, Providencia, and Morganella are Gram-negative bacteria.
- Human serum possesses antimicrobial properties.
Purpose of the Study:
- To investigate the susceptibility of Proteus, Providencia, and Morganella strains to human serum.
- To elucidate the mechanisms underlying the bactericidal action of human serum against these bacteria.
Main Methods:
- Bacterial survival was assessed after incubation with 50% human serum for 1 and 3 hours.
- Susceptible strains were tested with serum lacking classical or alternative complement pathways, or with lysozyme removed.
Main Results:
- Human serum exhibited bactericidal activity against the tested strains.
- Mechanisms involved complement activation via classical and/or alternative pathways, with lysozyme playing a crucial, strain-dependent role.
- Some strains required lysozyme for killing, while others were killed effectively without it.
Conclusions:
- The bactericidal effect of human serum on Proteus, Providencia, and Morganella is mediated by complement and lysozyme.
- Both classical and alternative complement pathways contribute to serum's bactericidal activity.
- Lysozyme's necessity varies, highlighting complex interactions in innate immunity.