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Improved methods for typing nontypeable isolates of group B streptococci
Jeffrey A Benson1, Aurea E Flores, Carol J Baker
1Department of Laboratory Medicine, University of Minnesota Medical School, Minneapolis 55455, USA.
International Journal of Medical Microbiology : IJMM
|July 26, 2002
Summary
Nontypeable Group B Streptococcus (GBS) isolates were analyzed using immunological and genetic methods. Many nontypeable GBS isolates were reclassified into specific capsular polysaccharide types, aiding GBS surveillance.
Area of Science:
- Microbiology
- Immunology
- Genetics
Background:
- Group B Streptococcus (GBS) classification relies on capsular polysaccharide (CPS) types and surface proteins.
- Nontypeable (NT) GBS isolates, lacking detectable CPS, still express surface proteins.
- Accurate GBS classification is crucial for epidemiological surveillance and vaccine development.
Purpose of the Study:
- To reclassify 91 nontypeable GBS isolates using combined immunological and genetic approaches.
- To evaluate the efficacy of mutanolysin and hot HCl extraction methods for CPS detection.
- To correlate DNA profiles from pulsed-field gel electrophoresis (PFGE) with CPS types.
Main Methods:
- Studied 91 NT GBS isolates from pregnant women, non-pregnant women, and neonates.
- Optimized CPS production using glucose and sodium phosphate in Todd-Hewitt broth (THB).
- Employed mutanolysin and hot HCl for cell extraction, double immunodiffusion (DD) with antisera for CPS typing, and SmaI-digested PFGE for DNA analysis.
Main Results:
- Mutanolysin extraction reclassified 13.2% (12/91) of NT GBS isolates as typeable.
- Hot HCl extraction identified only 4 of these 12 isolates.
- PFGE analysis revealed that 80.8% (63/78) of remaining NT isolates possessed DNA profiles similar to known GBS types.
Conclusions:
- Combined mutanolysin extraction and PFGE effectively reclassify NT GBS isolates.
- These methods enhance the accuracy of GBS epidemiological surveillance.
- Improved classification supports ongoing GBS vaccine trials and understanding of GBS pathogenesis.