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Penicillin-resistant variants of pneumococci
Abstract:
All of the 74 strains of pneumococci isolated from human infections from 1963 to 1964 proved to be uniformly and highly susceptible to penicillin. Of these strains, 15 were identified by capsule-swelling reactions and were submitted to serial transfer in the presence of increasing concentrations of penicillin. Highly penicillin-resistant mutants were selected from 14 of the 15 strains, whereas one strain was moderately resistant. Of these mutants, 11 could still react with specific antiserum, and all of the mutants could be identified by fermentation reactions and optochin inhibition. The in vitro development of penicillin resistance in these mutants did not result in a change in cell-wall composition sufficient to diminish bile solubility. The possibility of encountering rising penicillin resistance among pneumococci, as well as the possibility that such mutants may react atypically, should be kept in mind.
Insights
Penicillin resistance in pneumococci was investigated. Most strains were susceptible, but resistant mutants were developed in vitro, highlighting potential challenges in treatment.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Pneumococci (Streptococcus pneumoniae) are significant human pathogens.
- Penicillin was the primary treatment for pneumococcal infections during the study period.
- Understanding antimicrobial susceptibility is crucial for effective treatment strategies.
Purpose of the Study:
- To assess the in vitro susceptibility of pneumococcal strains to penicillin.
- To investigate the development of penicillin resistance in pneumococci through serial transfer.
- To characterize the properties of penicillin-resistant pneumococcal mutants.
Main Methods:
- Isolation and identification of 74 pneumococcal strains from human infections (1963-1964).
- Capsule-swelling reactions for strain identification.
- Serial transfer of selected strains in increasing penicillin concentrations to select for resistant mutants.
- Characterization of mutants using fermentation reactions, optochin inhibition, and bile solubility tests.
Main Results:
- All 74 initial pneumococcal strains were highly susceptible to penicillin.
- Penicillin-resistant mutants were successfully selected from 14 of 15 tested strains.
- Eleven resistant mutants retained their ability to react with specific antiserum.
- Mutant resistance development did not alter cell-wall composition enough to affect bile solubility.
Conclusions:
- In vitro development of penicillin resistance in pneumococci is achievable.
- Emerging penicillin resistance in pneumococci is a potential clinical concern.
- Penicillin-resistant pneumococcal mutants may exhibit atypical characteristics, requiring careful identification.