Phenotypic and molecular characterization of hyperpigmented group B Streptococci

Area of Science:

• Microbiology
• Molecular Biology
• Infectious Diseases

Background:

• Group B Streptococcus (GBS) causes severe infections in vulnerable populations.
• The β-hemolysin/cytolysin, encoded by the cyl operon, is a key GBS virulence factor.
• Hyperpigmented GBS isolates are often hyperhemolytic, with altered virulence gene expression linked to the CovS/R regulatory system.

Purpose of the Study:

• To investigate the role of the CovS/R regulatory system in virulence factor production in clinical GBS isolates.
• To correlate pigment production and hemolytic activity with molecular and transcriptional changes in GBS.

Main Methods:

• Prospective collection and analysis of 10 hyperpigmented GBS isolates from clinical samples (2008-2012).
• Phenotypic characterization including spectrophotometry for pigment analysis and hemolytic activity assays.
• Molecular analysis of the cyl operon and covR gene sequence.
• Transcriptional analysis of virulence factors.

Main Results:

• Spectrophotometry data for pigment absorbance peaks significantly correlated with hemolytic activity.
• The cyl operon was conserved across all isolates.
• Mutations in the covR gene were identified in five isolates, with one mutation abrogating the CovR binding site to cylX.
• Results support previous findings on CovR-deficient mutants but indicate potential alternative pathways for virulence factor production.

Conclusions:

• The CovS/R system plays a role in regulating GBS virulence factors, including β-hemolysin/cytolysin and CAMP factor.
• Mutations in covR can lead to altered pigment and hemolytic activity.
• Other molecular pathways, beyond the CovS/R system, may contribute to virulence factor production in some clinical GBS isolates.