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Experimental infection with parent and L-phase variants of Neisseria meningitidis
Abstract:
Thirty-six strains of Neisseria meningitidis, including groups A, B, and C, produced L forms in vitro in the presence of an osmotic stabilizer and high concentrations of horse serum using penicillin as the transforming agent. Transformation to L growth occurred most readily among strains recently isolated from patients, and an unusually high rate of transformation was observed in 7 of the 36 strains. Revertant L strains developed diplococcal colonies on blood-agar and L colonies on sucrose-serum-penicillin-agar-always in a ratio of approximately 10 to 100 diplococcal colonies to 1 L colony. Using mucin as a host depressant, comparison was made between parent and revertant L strains of their initial pathogenicity and development of virulence by serial mouse passage. In general, revertant L strains showed the same pathogenic characteristics as the parent. Heart blood cultures from mice dying of infection with revertant L strains retained their ability to grow as L forms on penicillin media. Three stable L strains were completely avirulent for mice, although persistence of L forms could be demonstrated in peritoneal exudate for 6 days after inoculation.
Insights
Neisseria meningitidis can transform into L-forms in vitro using penicillin. These meningococcal L-forms generally retained pathogenicity, showing similar virulence to parent strains in mouse models.
Area of Science:
- Microbiology
- Bacteriology
- Pathogen Transformation
Background:
- Neisseria meningitidis is a significant human pathogen.
- L-forms are cell-wall-deficient variants of bacteria that can arise under specific conditions.
- Understanding bacterial L-forms is crucial for comprehending microbial adaptation and pathogenesis.
Purpose of the Study:
- To investigate the in vitro induction of L-forms from Neisseria meningitidis strains.
- To compare the pathogenicity and virulence of parent strains and their derived L-forms.
- To assess the stability and characteristics of revertant L-forms.
Main Methods:
- Induction of L-forms using penicillin and osmotic stabilizers on Neisseria meningitidis strains.
- Culturing of L-forms on specialized agar media (sucrose-serum-penicillin-agar).
- Assessment of pathogenicity and virulence through serial mouse passage using mucin as a host depressant.
Main Results:
- Thirty-six Neisseria meningitidis strains (groups A, B, C) successfully produced L-forms in vitro.
- Transformation occurred readily in recently isolated strains, with 7 strains showing unusually high transformation rates.
- Revertant L-strains generally exhibited similar pathogenicity to parent strains; however, three stable L-strains were avirulent in mice.
Conclusions:
- Neisseria meningitidis can be readily transformed into L-forms with retained pathogenicity.
- Revertant L-forms largely maintain the virulence characteristics of their parent strains.
- The study highlights the potential for L-form generation and their implications in meningococcal disease dynamics.