title: Phenotypic and molecular characterization of hyperpigmented group B Streptococci.
abstract: Group B Streptococcus (GBS) causes invasive infections in neonates, older adults and patients with comorbidities. β-hemolysin/cytolysin is an important GBS virulence factor. It is encoded by the cyl operon and confers GBS hemolytic activity. Isolates displaying hyperpigmentation are typically hyperhemolytic. Comparison of clonally identical isolates displaying different levels of pigmentation has shown transcriptional dysregulation due to mutations in components of the control of the virulence S/R (CovS/R) regulatory system. In addition, hyperpigmented isolates show decreased CAMP factor and decreased capsule thickness. In analogy to findings in group A Streptococcus, a pivotal role of CovS/R has been proposed in the host-pathogen interaction of invasive GBS infection. However, corresponding investigations on multiple clinical GBS isolates have not been performed. We prospectively collected hyperpigmented isolates found in a diagnostic laboratory and performed phenotypic, molecular and transcriptional analyses. In the period from 2008 to 2012, we found 10 isolates obtained from 10 patients. The isolates reflected both invasive pathogens and colonizers. In three cases, clonally identical but phenotypically different variants were also found. Hence, the analyses included 13 isolates. No capsular serotype was found to be significantly more frequent. Bacterial pigments were analyzed via spectrophotometry and for their hemolytic activity. Data obtained for typical absorbance spectra peaks correlated significantly with hemolytic activity. Molecular analysis of the cyl operon showed that it was conserved in all isolates. The covR sequence displayed mutations in five isolates; in one isolate, the CovR binding site to cylX was abrogated. Our results on clinical isolates support previous findings on CovR-deficient isogenic mutants, but suggest that - at least in some clinical isolates - for β-hemolysin/cytolysin and CAMP factor production, other molecular pathways may be involved.
authors.affiliation: Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
authors.forename: Agnese
authors.initials: A
authors.lastname: Lupo
authors.affiliation: Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
authors.forename: Corinne
authors.initials: C
authors.lastname: Ruppen
authors.affiliation: Institute of Parasitology, University of Bern, Bern, Switzerland.
authors.forename: Andrew
authors.initials: A
authors.lastname: Hemphill
authors.affiliation: Institute of Medical Microbiology and Hygiene, University Hospital Ulm, Ulm, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Spellerberg
authors.affiliation: Institute for Infectious Diseases, University of Bern, Bern, Switzerland; Department of Infectious Diseases, Bern University Hospital, Bern, Switzerland. Electronic address: parham.sendi@ifik.unibe.ch.
authors.forename: Parham
authors.initials: P
authors.lastname: Sendi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002675:Child, Preschool; D017124:Conserved Sequence; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006460:Hemolysin Proteins / Q000235:genetics / Q000378:metabolism; D006461:Hemolysis; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009876:Operon; D054353:Perforin / Q000235:genetics / Q000378:metabolism; D010860:Pigments, Biological / Q000032:analysis*; D017422:Sequence Analysis, DNA; D065288:Serogroup; D013053:Spectrophotometry; D013290:Streptococcal Infections / Q000382:microbiology; D013292:Streptococcus agalactiae / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D055815:Young Adult
chemical_list: D006460:Hemolysin Proteins; D010860:Pigments, Biological; D054353:Perforin
keywords: Granadaene pigment; Group B streptococci; Streptococcus agalactiae; covS/R; cyl operon; β-Hemolysin