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Type variation of strains of Streptococcus pneumoniae in capsular serogroup 15
Abstract:
The repeated finding of two capsular types of Streptococcus pneumoniae in serogroup 15 in infected exudate from the middle ear led to the demonstration of type variation in pneumococcal types 15B and 15C. Determination of the chemical composition of the capsular polysaccharides of the pneumococci in serogroup 15 showed that the observed variation was related to the presence of an O-acetyl group in the capsular polysaccharide of type 15B which was lacking from the otherwise identical polysaccharide of type 15C. The phenomenon appears similar to that reported in several other bacterial species in which it has been ascribed to labile inversion of a segment of DNA.
Insights
Two capsular types of Streptococcus pneumoniae, 15B and 15C, were identified, differing by an O-acetyl group. This variation in pneumococcal serogroup 15 may stem from DNA segment inversion.
Area of Science:
- Microbiology
- Bacterial genetics
- Immunology
Background:
- Streptococcus pneumoniae causes various infections, including otitis media.
- Pneumococcal capsular types are crucial for serotyping and vaccine development.
- Serogroup 15 pneumococci exhibit distinct capsular types, 15B and 15C.
Purpose of the Study:
- To investigate the observed type variation within Streptococcus pneumoniae serogroup 15.
- To elucidate the chemical basis for the difference between pneumococcal types 15B and 15C.
- To explore potential genetic mechanisms underlying this capsular variation.
Main Methods:
- Analysis of infected middle ear exudate samples.
- Chemical composition determination of capsular polysaccharides.
- Comparison of polysaccharide structures between pneumococcal types 15B and 15C.
Main Results:
- Two distinct capsular types, 15B and 15C, were confirmed in Streptococcus pneumoniae.
- Type 15B polysaccharide contains an O-acetyl group, absent in type 15C.
- The polysaccharides of types 15B and 15C are otherwise chemically identical.
Conclusions:
- The O-acetyl group differentiates Streptococcus pneumoniae types 15B and 15C.
- This capsular variation is potentially linked to labile DNA inversion, a phenomenon observed in other bacteria.
- Understanding this variation is important for pneumococcal typing and epidemiology.