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Effect of human airway lysozyme on the in vitro growth of type I Streptococcus pneumoniae
J Jacquot1, E Puchelle, J M Zahm
1Groupe d'Etude des Systèmes Mucociliaires (GEMUC), INSERM Unité 314 Faculté de Médecine, Reims, France.
Abstract:
The effects of purified human airway lysozyme and hen egg-white lysozyme on growth rate and viability of growing type I Streptococcus pneumoniae were studied. Exposure of bacteria to human and hen lysozyme at the same final concentration (100 micrograms/ml) for 1.5-4.5 h resulted in a marked reduction of the number of colony-forming units per ml compared to control cultures. After a 1.5-h exposure to human or hen lysozyme, the remaining percentage of colony forming units per ml was 54% and 69%, respectively. The onset of growth only appeared after a 3.5-h exposure period for human lysozyme whereas it began at 2.5 h for hen lysozyme. After 3.5 h and 4.5 h of exposure, the number of colony-forming units was significantly lower (p less than 0.05) in human lysozyme-treated bacteria cultures compared to control cultures. Parallel electron microscopic observations of Streptococcus pneumoniae cultures confirmed that the density of pneumococci was less in the presence of either human lysozyme or hen lysozyme in comparison to control cultures, and showed the presence of numerous long, ribbon-like material and cytoplasmic condensations liberated in the culture medium.
Insights
Human airway lysozyme and hen egg-white lysozyme significantly reduced Streptococcus pneumoniae growth. Human lysozyme demonstrated a more potent inhibitory effect on bacterial viability and delayed growth onset compared to hen lysozyme.
Area of Science:
- Microbiology
- Biochemistry
- Enzymology
Background:
- Lysozymes are enzymes with bactericidal properties.
- Streptococcus pneumoniae is a significant human pathogen.
- Understanding lysozyme's effect on S. pneumoniae is crucial for developing new antimicrobial strategies.
Purpose of the Study:
- To investigate the impact of human airway lysozyme and hen egg-white lysozyme on the growth and viability of Streptococcus pneumoniae.
- To compare the efficacy of human and hen lysozymes against S. pneumoniae.
Main Methods:
- Bacterial cultures of Streptococcus pneumoniae were exposed to purified human airway lysozyme and hen egg-white lysozyme at a concentration of 100 µg/ml.
- Bacterial viability was assessed by counting colony-forming units (CFUs) over time (1.5-4.5 hours).
- Electron microscopy was used to observe morphological changes in S. pneumoniae.
Main Results:
- Both human and hen lysozymes markedly reduced CFU counts compared to controls.
- After 1.5 hours, 54% of CFUs remained with human lysozyme and 69% with hen lysozyme.
- Human lysozyme delayed growth onset to 3.5 hours, while hen lysozyme allowed growth to resume at 2.5 hours.
- Electron microscopy revealed reduced pneumococcal density and the presence of cellular debris in lysozyme-treated cultures.
Conclusions:
- Human airway lysozyme exhibits a stronger inhibitory effect on Streptococcus pneumoniae growth and viability than hen egg-white lysozyme.
- Lysozyme treatment induces significant morphological changes in S. pneumoniae.
- These findings suggest potential therapeutic applications for human lysozyme in combating pneumococcal infections.