Differences in virulence for mice among Streptococcus pneumoniae strains of capsular types 2, 3, 4, 5, and 6 are not attributable to differences in pneumolysin production
Related Experiment Videos
K A Benton1, J C Paton, D E Briles
1Department of Microbiology, The University of Alabama at Birmingham, USA. kbenton@uab.edu
Abstract:
We observed that differences in the in vivo growth kinetics of pneumococcal strains of capsular types 3, 4, 5, and 6 were reminiscent of differences that we had previously reported for type 2 strain D39 and its pneumolysin-deficient mutant, PLN. Capsular type 2 Streptococcus pneumoniae D39 exhibits exponential growth in the blood of XID mice until the death of the mice at 24 to 36 h. In contrast, PLN reaches a plateau in growth that is maintained for several days. Capsular type 3 and 5 strains exhibited exponential growth and caused rapid death of XID mice following intravenous challenge, similar to the observation with D39. Strains of capsular types 4 and 6 exhibited growth kinetics reminiscent of PLN. Since the observed differences in the pathogenesis of types 3 and 5 compared to 4 and 6 were reminiscent of the effects of pneumolysin deficiency in type 2, we examined the levels of in vitro pneumolysin production for the entire panel of strains. The onset of pneumolysin production in most strains was rapid and occurred near the end of log-phase growth. Differences in in vivo growth patterns of capsular type 2, 3, 4, 5, and 6 strains were not found to be associated with differences in the levels of pneumolysin.
Insights
Pneumococcal strains showed varied growth patterns in mice, similar to a pneumolysin-deficient mutant. These differences in Streptococcus pneumoniae pathogenesis were not linked to pneumolysin levels, suggesting other factors influence in vivo growth.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Background:
- Streptococcus pneumoniae exhibits diverse capsular types with varying virulence.
- Pneumolysin is a key virulence factor in S. pneumoniae, but its role across different capsular types is not fully understood.
- Previous studies highlighted differences in growth kinetics between S. pneumoniae D39 and its pneumolysin-deficient mutant.
Purpose of the Study:
- To investigate the in vivo growth kinetics of different Streptococcus pneumoniae capsular types (3, 4, 5, and 6) in mice.
- To compare these growth patterns with previously studied type 2 strains and their pneumolysin-deficient counterparts.
- To determine if observed differences in pathogenesis correlate with pneumolysin production levels.
Main Methods:
- Intravenous challenge of XID mice with S. pneumoniae strains of capsular types 2, 3, 4, 5, and 6.
- Monitoring of bacterial growth kinetics in mouse blood.
- Measurement of pneumolysin production in vitro for all tested strains.
Main Results:
- Capsular types 3 and 5 strains showed exponential growth and rapid mouse mortality, similar to S. pneumoniae D39.
- Capsular types 4 and 6 strains exhibited growth kinetics resembling the pneumolysin-deficient mutant (PLN), with growth plateau.
- In vitro pneumolysin production levels did not correlate with the observed in vivo growth differences across the tested capsular types.
Conclusions:
- In vivo growth kinetics of S. pneumoniae vary among capsular types.
- The observed differences in pathogenesis are not solely explained by pneumolysin production levels.
- Further research is needed to identify other factors contributing to the distinct in vivo behavior of different S. pneumoniae strains.