Combining Microarray Technology and Molecular Epidemiology to Identify Genes Associated with Invasive Group BStreptococcus

Lixin Zhang,Joan Debusscher,Betsy Foxman,Carl F Marrs,Usha Reddi,Anne N Styka,Stephanie M Borchardt,Puja Mehta,Usha Srinivasan,Parvathy Pillai,Sheng Li

doi:10.1155/2008/314762

Abstract

Many bacterial species function as both commensals and pathogens; we used this dual nature to develop a high-throughput molecular epidemiological approach to identifying bacterial virulence genes. We applied our approach to Group B Streptococcus (GBS). Three representative commensal and one invasive GBS isolates were selected as tester strains from a population-based collection. We used microarray-based comparative genomic hybridization to identify open reading frames (ORFs) present in two sequenced invasive strains, but absent or divergent in tester strains. We screened 23 variable ORFs against 949 GBS isolates using a GBS Library on a Slide (LOS) microarray platform. Four ORFs occurred more frequently in invasive than commensal isolates, and one appeared more frequently in commensal isolates. Comparative hybridization using an oligonucleotide microarray, combined with epidemiologic screening using the LOS microarray platform, enabled rapid identification of bacterial genes potentially associated with pathogenicity.

Highlights

Group B Streptococcus (GBS), or Streptococcus agalactiae, a common bowel inhabitant, frequently colonizes the vagina, urethra, and pharynx asymptomatically
In a previous study of E. coli, we presented an approach of bacterial gene identification and evaluation that relied on epidemiologic information for selecting isolates for genomic subtraction and screening of epidemiologically defined collections for evaluation of the significance of genes identified through genomic subtraction [24]
We characterized the diversity of 882 colonizing isolates from a population-based longitudinal study of healthy male and nonpregnant female college students [28] using pulsed-field gel electrophoresis (PFGE) and serotyping

Summary

Introduction

Group B Streptococcus (GBS), or Streptococcus agalactiae, a common bowel inhabitant, frequently colonizes the vagina, urethra, and pharynx asymptomatically. Among the nine known GBS capsular serotypes, serotypes Ia, III, and V cause the majority of GBS disease in the United States [1, 6,7,8]. By pulsed-field gel electrophoresis (PFGE), disease-causing isolates have limited heterogeneity within a serotype (reviewed in Schuchat, 1998 [2]) while colonizing isolates are quite heterogeneous [14] within a particular serotype, suggesting that invasive isolates have distinctive features which enhance pathogenesis. Advances have been made in the understanding of classic GBS traits, such as capsular polysaccharide, β-hemolysin, C5a peptidase, and immunogenic surface proteins [16,17,18,19], our understanding of the pathogenesis of GBS infections is limited: little is known about which bacterial genetic factors contribute to virulence or transmission of pathogenic strains

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Conclusion