Increased Pilus Production Conferred by a Naturally Occurring Mutation Alters Host-Pathogen Interaction in Favor of Carriage in Streptococcus pyogenes

Abstract

Studies of the human pathogen group A Streptococcus (GAS) define the carrier phenotype to be an increased ability to adhere to and persist on epithelial surfaces and a decreased ability to cause disease. We tested the hypothesis that a single amino acid change (Arg135Gly) in a highly conserved sensor kinase (LiaS) of a poorly defined GAS regulatory system contributes to a carrier phenotype through increased pilus production. When introduced into an emm serotype-matched invasive strain, the carrier allele (the gene encoding the LiaS protein with an arginine-toglycine change at position 135 [liaS R135G ]) recapitulated a carrier phenotype defined by an increased ability to adhere to mucosal surfaces and a decreased ability to cause disease. Gene transcript analyses revealed that the liaS mutation significantly altered transcription of the genes encoding pilus in the presence of bacitracin. Elimination of pilus production in the isogenic carrier mutant decreased its ability to colonize the mouse nasopharynx and to adhere to and be internalized by cultured human epithelial cells and restored the virulence phenotype in a mouse model of necrotizing fasciitis. We also observed significantly reduced survival of the isogenic carrier mutant compared to that of the parental invasive strain after exposure to human neutrophils. Elimination of pilus in the isogenic carrier mutant increased the level of survival after exposure to human neutrophils to that for the parental invasive strain. Together, our data demonstrate that the carrier mutation (liaS R135G ) affects pilus expression. Our data suggest new mechanisms of pilus gene regulation in GAS and that the invasiveness associated with pilus gene regulation in GAS differs from the enhanced invasiveness associated with increased pilus production in other bacterial pathogens.

ExPortal and the LiaFSR Regulatory System Coordinate the Response to Cell Membrane Stress in Streptococcus pyogenes

“…S2C ). LiaR has previously been shown to directly regulate the gene encoding the RNA polymerase-binding protein SpxA in S. mutans ( 25 ) (SpxA2 in GAS) and has been used as an indicator of LiaFSR activation in GAS ( 26 ). Thus, to ensure that chimeric LiaF and LiaS proteins remained functional and that dPM did not alter LiaFSR activation, we assayed spxA2 transcript levels following dPM exposure and observed no significant transcript level differences relative to the untreated cells ( Fig.…”

RocA Has Serotype-Specific Gene Regulatory and Pathogenesis Activities in Serotype M28 Group A Streptococcus

“…Selected virulence factor genes with increased transcript levels in the isogenic ΔrocA mutant strain include nga (encoding NAD ϩ -glycohydrolase [ (80). Selected virulence factor genes with decreased transcript levels in the isogenic ΔrocA strain include M28_Spy0109 (encoding pilin protein) (50,81), the sag operon (carrying streptolysin S biosynthesis genes) (82), grab (encoding protein-Grelated ␣ 2 -macroglobulin binding protein) (83), ska (encoding streptokinase [SKA]) (84), and speB (encoding streptococcal cysteine protease B) (85).…”

Identification and Characterization of Serotype-Specific Variation in Group A Streptococcus Pilus Expression

“…However, while a lower pH increased the level of pilus expression, no pili were produced in the sample at neutral pH, consistent with our data. Note that the regulators responsible for this pH-specific regulation of pilus expression are unknown, but recent data indicate that the LiaFSR proteins may contribute (56,57). Third, T typing is a serology-based method for dividing GAS isolates into different types (T types), and the major pilus protein (Tee) is the T antigen.…”