title: The majority of 9,729 group A streptococcus strains causing disease secrete SpeB cysteine protease: pathogenesis implications.
abstract: Group A streptococcus (GAS), the causative agent of pharyngitis and necrotizing fasciitis, secretes the potent cysteine protease SpeB. Several lines of evidence suggest that SpeB is an important virulence factor. SpeB is expressed in human infections, protects mice from lethal challenge when used as a vaccine, and contributes significantly to tissue destruction and dissemination in animal models. However, recent descriptions of mutations in genes implicated in SpeB production have led to the idea that GAS may be under selective pressure to decrease secreted SpeB protease activity during infection. Thus, two divergent hypotheses have been proposed. One postulates that SpeB is a key contributor to pathogenesis; the other, that GAS is under selection to decrease SpeB during infection. In order to distinguish between these alternative hypotheses, we performed casein hydrolysis assays to measure the SpeB protease activity secreted by 6,775 GAS strains recovered from infected humans. The results demonstrated that 84.3% of the strains have a wild-type SpeB protease phenotype. The availability of whole-genome sequence data allowed us to determine the relative frequencies of mutations in genes implicated in SpeB production. The most abundantly mutated genes were direct transcription regulators. We also sequenced the genomes of 2,954 GAS isolates recovered from nonhuman primates with experimental necrotizing fasciitis. No mutations that would result in a SpeB-deficient phenotype were identified. Taken together, these data unambiguously demonstrate that the great majority of GAS strains recovered from infected humans secrete wild-type levels of SpeB protease activity. Our data confirm the important role of SpeB in GAS pathogenesis and help end a long-standing controversy.
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA rjolsen@houstonmethodist.org.
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Olsen
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Anjali
authors.initials: A
authors.lastname: Raghuram
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Concepcion
authors.initials: C
authors.lastname: Cantu
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Meredith H
authors.initials: MH
authors.lastname: Hartman
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Francisco E
authors.initials: FE
authors.lastname: Jimenez
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Lee
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Ashley
authors.initials: A
authors.lastname: Ngo
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Kelsey A
authors.initials: KA
authors.lastname: Rice
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Deborah
authors.initials: D
authors.lastname: Saddington
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Hannaka
authors.initials: H
authors.lastname: Spillman
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Chandni
authors.initials: C
authors.lastname: Valson
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA Department of Pediatrics, Baylor College of Medicine, Texas Children's Hospital, Houston, Texas, USA.
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Flores
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Beres
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: S Wesley
authors.initials: SW
authors.lastname: Long
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: Waleed
authors.initials: W
authors.lastname: Nasser
authors.affiliation: Center for Molecular and Translational Human Infectious Diseases Research, Department of Pathology and Genomic Medicine, Houston Methodist Research Institute and Hospital System, Houston, Texas, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Musser
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002364:Caseins / Q000737:chemistry; D062665:Epidemiological Monitoring; D005060:Europe / Q000453:epidemiology; D005098:Exotoxins / Q000235:genetics* / Q000378:metabolism; D019115:Fasciitis, Necrotizing / Q000453:epidemiology / Q000382:microbiology / Q000473:pathology; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D009154:Mutation; D010612:Pharyngitis / Q000453:epidemiology / Q000382:microbiology / Q000473:pathology; D011323:Primates; D059748:Proteolysis; D012703:Serotyping; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000473:pathology; D013297:Streptococcus pyogenes / Q000145:classification / Q000201:enzymology* / Q000235:genetics* / Q000472:pathogenicity; D014158:Transcription, Genetic; D014481:United States / Q000453:epidemiology; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D002364:Caseins; D005098:Exotoxins; C027951:erythrogenic toxin