title: Regulation of capsule gene expression by group A Streptococcus during pharyngeal colonization and invasive infection.
abstract: Capsular polysaccharide production by group A Streptococcus (GAS) is controlled by transcription of the has operon that encodes the enzymes uniquely required for synthesis of the hyaluronic acid polysaccharide. To investigate the regulation of capsule gene expression during infection, we developed a reporter strain of GAS in which the has operon promoter directed transcription of green fluorescent protein (GFP). Gfp expression was triggered within minutes after introduction of the reporter strain into the peritoneal cavity of mice, as evidenced by the recovery of highly fluorescent GAS from the peritoneum 1 h after challenge. Capsule gene expression was also stimulated in the bloodstream of infected mice, as intensely fluorescent bacteria were observed in blood samples collected after either intraperitoneal or intravenous challenge. Using a similar approach, we also observed rapid induction of capsule gene expression in bacteria inoculated into the pharynx of baboons. Compared to the inoculum, increased green fluorescence was recorded in bacteria recovered from throat swabs collected 1 h after inoculation in all five animals studied. We conclude that introduction of GAS into the pharynx or into deep tissues results in rapid induction of has operon expression, a critical adaptive response that enhances GAS survival in the infected host.
authors.affiliation: Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: I
authors.initials: I
authors.lastname: Gryllos
authors.forename: C
authors.initials: C
authors.lastname: Cywes
authors.forename: M H
authors.initials: MH
authors.lastname: Shearer
authors.forename: M
authors.initials: M
authors.lastname: Cary
authors.forename: R C
authors.initials: RC
authors.lastname: Kennedy
authors.forename: M R
authors.initials: MR
authors.lastname: Wessels
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000096:biosynthesis / Q000235:genetics*; D004195:Disease Models, Animal; D005260:Female; D005434:Flow Cytometry; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006801:Humans; D007202:Indicators and Reagents / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D009876:Operon / Q000235:genetics; D010215:Papio; D010537:Peritoneum / Q000382:microbiology; D010614:Pharynx / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013290:Streptococcal Infections / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000235:genetics* / Q000502:physiology; D013997:Time Factors
chemical_list: D007202:Indicators and Reagents; D008164:Luminescent Proteins; D011135:Polysaccharides, Bacterial; D011993:Recombinant Fusion Proteins; C036112:streptococcal polysaccharide group A; D049452:Green Fluorescent Proteins