Streptococcus agalactiae pulsed-field gel electrophoresis patterns cross capsular types.

Area of Science:

• Microbiology
• Genetics
• Epidemiology

Background:

• Streptococcus agalactiae exhibits significant genetic diversity, with multiple pulsed-field gel electrophoresis (PFGE) types often found within a single capsular serotype.
• Understanding the relationship between PFGE types and serotypes is crucial for accurate epidemiological investigations.

Purpose of the Study:

• To determine if Streptococcus agalactiae PFGE types correlate with specific serotypes within individuals.
• To assess the consistency of PFGE types and serotypes across different individuals from the same geographic region.

Main Methods:

• Classified 872 Streptococcus agalactiae isolates from 152 healthy individuals using PFGE and capsular serotyping.
• Analyzed the diversity and correlation between PFGE patterns and serotypes within and between individuals.

Main Results:

• Serotype V demonstrated high homogeneity (Simpson's diversity index 0.54), while serotypes III, II, and Ib were highly heterogeneous (Simpson's diversity index 0.90).
• Within-individual isolates sharing PFGE patterns consistently had identical capsular types.
• Across different individuals, identical PFGE types were sometimes associated with different serotypes.

Conclusions:

• Pulsed-field gel electrophoresis (PFGE) typing is a valid surrogate for capsular typing of Streptococcus agalactiae isolates from the same individual.
• PFGE typing is not a reliable surrogate for serotyping Streptococcus agalactiae isolates from different individuals.
• Capsular serotype alone is insufficient for defining epidemiological relatedness in Streptococcus agalactiae.