Emergence of Respiratory Streptococcus agalactiae Isolates in Cystic Fibrosis Patients

Vera Eickel,Barbara Kahl,Claudia Brandt,Angelika Dübbers,Peter Küster,Barbara Spellerberg,Beatrice Reinisch,Adam J Ratner

doi:10.1371/journal.pone.0004650

Abstract

Streptococcus agalactiae is a well-known pathogen for neonates and immunocompromized adults. Beyond the neonatal period, S. agalactiae is rarely found in the respiratory tract. During 2002–2008 we noticed S. agalactiae in respiratory secretions of 30/185 (16%) of cystic fibrosis (CF) patients. The median age of these patients was 3–6 years older than the median age CF patients not harboring S. agalactiae. To analyze, if the S. agalactiae isolates from CF patients were clonal, further characterization of the strains was achieved by capsular serotyping, surface protein determination and multilocus sequence typing (MLST). We found a variety of sequence types (ST) among the isolates, which did not substantially differ from the MLST patterns of colonizing strains from Germany. However serotype III, which is often seen in colonizing strains and invasive infections was rare among CF patients. The emergence of S. agalactiae in the respiratory tract of CF patients may represent the adaptation to a novel host environment, supported by the altered surfactant composition in older CF patients.

Highlights

IntroductionStreptococcus agalactiae (group B streptococci, GBS) is an important human pathogen causing invasive disease in neonates and immunocompromized adult patients
Streptococcus agalactiae is an important human pathogen causing invasive disease in neonates and immunocompromized adult patients
This study employed selective enrichment broth to optimize S. agalactiae recovery and was not performed in cystic fibrosis (CF) patients, which harbor a multitude of different bacteria in respiratory secretions

Summary

Introduction

Streptococcus agalactiae (group B streptococci, GBS) is an important human pathogen causing invasive disease in neonates and immunocompromized adult patients. In the years 2003, 2004 and 2005 more adult patients died following invasive S. agalactiae infections than invasive S. pyogenes disease (http://www.cdc.gov/ncidod/dbmd/ abcs/survreports/gbs05.pdf). These data suggest that the epidemiology of S. agalactiae is changing and that the bacteria are adapting to novel environments within the human host. In contrast to closely related bacterial species like Streptococcus pyogenes, S. agalactiae is only rarely seen as a colonizer in respiratory secretions from pediatric patients beyond the neonatal period [1,2]. A more recent comprehensive investigation of 465 CF patients for colonizing gram positive microorganisms isolated S. pyogenes in 4 samples but did not find a single patient colonized by S. agalactiae [4]

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