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The influence of penicillin on growth and morphology of Streptococcus pyogenes in vivo
Abstract:
The influence of penicillin (pc) on the growth, phagocytosis and killing of Streptococcus pyogenes was studied for an M protein positive (M+) and an M protein negative (M-) strain in vivo as well as in vitro. In vivo studies were based on a tissue cage model and the analyses were performed by CFU determinations and electron microscopic investigations. The M- strain was easily phagocytized with and without pc, but killing only occurred after pc treatment and thus the number of viable bacteria rapidly decreased under the influence of pc. M+ streptococci were not reduced in numbers by pc-treatment in vivo, but morphological changes and at high pc concentrations, phagocytosis could be seen. When this strain (M+) was cultivated in the absence of pc, the phagocytic cells were totally destroyed - a reaction that was prevented by penicillin. Variations in surface morphology of the two strains seem to influence the differences in sensitivity to penicillin, phagocytosis and killing.
Insights
Penicillin effectively kills M protein-negative Streptococcus pyogenes but not M protein-positive strains. Penicillin also protects phagocytic cells from M+ Streptococcus pyogenes.
Area of Science:
- Microbiology
- Immunology
- Pharmacology
Background:
- Streptococcus pyogenes exhibits varying resistance to penicillin.
- M protein influences bacterial interaction with host immune cells.
Purpose of the Study:
- To investigate penicillin's effect on M+ and M- Streptococcus pyogenes growth, phagocytosis, and killing.
- To compare in vivo and in vitro responses to penicillin.
Main Methods:
- Tissue cage model for in vivo studies.
- Colony-forming unit (CFU) determinations.
- Electron microscopy for morphological analysis.
Main Results:
- Penicillin treatment led to rapid killing of M- Streptococcus pyogenes.
- M+ Streptococcus pyogenes showed reduced susceptibility to penicillin in vivo, with morphological changes observed.
- Penicillin protected phagocytic cells from M+ Streptococcus pyogenes-induced destruction in vitro.
Conclusions:
- Bacterial surface morphology, particularly M protein expression, significantly impacts penicillin efficacy and phagocytosis.
- Penicillin's effectiveness against Streptococcus pyogenes is strain-dependent.