M proteins of group C streptococci isolated from patients with acute pharyngitis.
ABSTRACT: We studied 15 strains of group C (Streptococcus equi subsp. equisimilis) [corrected] isolated from the throats of college students with acute pharyngitis and 5 strains isolated from patients with noninfectious problems. Nineteen of the 20 strains resisted phagocytic killing during incubation in normal human blood, suggesting that they might express M proteins. Genomic DNA from all 20 strains hybridized with a probe corresponding to the carboxyterminal one-third of the group A M-protein gene emm24, a region that is highly conserved among M proteins of group A and group G streptococci. The DNA sequences of the N-terminal (variable) regions of the M-protein-encoding genes from two disease-associated group C isolates and one control isolate were determined. The predicted amino acid sequences of the two pharyngitis strains were identical and were 88% homologous to the amino acid sequence of a group G M-protein gene. The predicted terminal amino acid sequence of the control strain does not correspond to any such sequences in the GenBank database. All three strains studied possess the conserved region domain common to class I group A M-protein types epidemiologically associated with rheumatic fever. These studies demonstrate the presence of M proteins in strains of S. equi subsp. equisimilis [corrected] isolated in cases of endemically occurring acute pharyngitis. Certain of these proteins are similar to those of group G streptococci, while others may represent new M types. The similarity in structure and function between M proteins of nonrheumatogenic serogroups and those of rheumatogenic group A streptococci suggests that factors other than or in addition to M protein per se are likely involved in the pathogenesis of rheumatic fever.
Project description:The secreted cysteine proteinase SpeB is an important virulence factor of group A streptococci (GAS), whereby SpeB activity varies widely among strains. To establish the degree to which SpeB activity correlates with disease, GAS organisms were recovered from patients with pharyngitis, impetigo, invasive disease or acute rheumatic fever (ARF), and selected for analysis using rigorous sampling criteria; >300 GAS isolates were tested for SpeB activity by casein digestion assays, and each GAS isolate was scored as a SpeB-producer or non-producer. Highly significant statistical differences (p < 0.01) in SpeB production are observed between GAS recovered from patients with ARF (41.5% SpeB-non-producers) compared to pharyngitis (20.5%), invasive disease (16.7%), and impetigo (5.5%). SpeB activity differences between pharyngitis and impetigo isolates are also significant, whereas pharyngitis versus invasive isolates show no significant difference. The disproportionately greater number of SpeB-non-producers among ARF-associated isolates may indicate an altered transcriptional program for many rheumatogenic strains and/or a protective role for SpeB in GAS-triggered autoimmunity.
Project description:Twelve strains (the largest number ever reported) of group C and G(1) streptococci (GCS and GGS, respectively) that caused streptococcal toxic shock syndrome (STSS) were collected and characterized. Eleven strains were identified as Streptococcus dysgalactiae subsp. equisimilis, and one strain was identified as Streptococcus equi subsp. zooepidemicus. We found that it was the first reported case of STSS caused by S. equi subsp. zooepidemicus. Cluster analysis according to the 16S rRNA gene (rDNA) sequences revealed that the S. dysgalactiae strains belonged to clusters I and II, both of which were closely related. The emm types and the restriction patterns of chromosomal DNA measured by pulsed-field gel electrophoresis were highly variable in these strains except BL2719 and N1434. The 16S rDNA sequences and other characteristics of these two strains were indistinguishable, suggesting the clonal dissemination of this particular S. dysgalactiae strain in Japan. As the involvement of superantigens in the pathogenesis of group A streptococcus-related STSS has been suggested, we tried to detect known streptococcal superantigens in GCS and GGS strains. However, only the spegg gene was detected in seven S. dysgalactiae strains, with none of the other superantigen genes being detected in any of the strains. However, the sagA gene was detected in all of the strains except Tokyo1291. In the present study no apparent factor(s) responsible for the pathogenesis of STSS was identified, although close genetic relationships of GCS and GGS strains involved in this disease were suggested.
Project description:Streptococcus dysgalactiae subsp. equisimilis (groups C and G streptococci [GCS/GGS]) is an increasingly recognized human pathogen, although it may follow indirect pathways. Prospective surveillance of selected households in 3 remote Aboriginal communities in Australia provided 337 GCS/GGS isolates that were emm sequence-typed. Lancefield group C isolates (GCS) were localized to specific households and group G isolates (GGS) were more evenly distributed. GCS/GGS was more frequently recovered from the throat than group A streptococci (GAS [S. pyogenes]) but rarely recovered from skin sores, and then only with Staphylococcus aureus or GAS. Symptomatic GGS/GGC pharyngitis was also rare. Specific emm sequence types of GCS/GGS did not appear to cycle through the communities (sequential strain replacement) in a manner suggesting acquisition of type-specific immunity. These communities already have high levels of streptococcal and poststreptococcal disease. GCS/GGS may increase in importance as it acquires key virulence factors from GAS by lateral gene transfer.
Project description:Based on a pair of primers developed initially for differentiating the anginosus group from other viridans streptococci, the PCR reported here can also differentiate between members of the anginosus group and Streptococcus dysgalactiae subsp. equisimilis among beta-hemolytic group C and G streptococci. The resulting 742-bp PCR product was specific for members of the anginosus group, although a smaller, nonspecific product (361 bp) was generated from S. dysgalactiae subsp. equisimilis. Restriction digestion of the amplicon with XbaI and BsmI further differentiated Streptococcus anginosus from Streptococcus constellatus within the anginosus group.
Project description:For three human blood culture isolates of beta-hemolytic streptococci with Lancefield's serogroup A antigen, phylogenetic analysis of the 16S rRNA genes confirmed biochemical identification as Streptococcus dysgalactiae subsp. equisimilis. Genes encoding M or M-like proteins, which are considered to be major virulence determinants in streptococci, were detected in all of these strains. Our data clearly demonstrate that for beta-hemolytic streptococci, the species assignment should not be based on the results of serogrouping alone.
Project description:Beta-hemolytic group C and G streptococci cause a considerable invasive disease burden and sometimes cause disease outbreaks. Little is known about the critical epidemiologic parameter of genetic relatedness between isolates. We determined the emm types of 334 Streptococcus dysgalactiae subsp. equisimilis isolates, and attempted emm typing of 5 Streptococcus canis isolates from a recent population-based surveillance for invasive isolates. Thirty-four emm types were observed, including one from S. canis. We formulated multilocus sequence typing (MLST) primers with six of the seven loci corresponding to the Streptococcus pyogenes MLST scheme. We performed MLST with 65 of the 334 surveillance isolates (61 S. dysgalactiae subsp. equisimilis isolates, 4 S. canis isolates) to represent each emm type identified, including 2 to 3 isolates for each of the 25 redundantly represented emm types. Forty-one MLST sequence types (STs) were observed. Isolates within 16 redundantly represented S. dysgalactiae subsp. equisimilis emm types shared identical or nearly identical STs, demonstrating concordance between the emm type and genetic relatedness. However, seven STs were each represented by two to four different emm types, and 7 of the 10 S. dysgalactiae subsp. equisimilis eBURST groups represented up to six different emm types. Thus, S. dysgalactiae subsp. equisimilis isolates were similar to S. pyogenes isolates, in that strains of the same emm type were often highly related, but they differed from S. pyogenes, in that S. dysgalactiae subsp. equisimilis strains with identical or closely similar STs often exhibited multiple unrelated emm types. The phylogenetic relationships between S. dysgalactiae subsp. equisimilis and S. pyogenes alleles revealed a history of interspecies recombination, with either species often serving as genetic donors. The four S. canis isolates shared highly homologous alleles but were unrelated clones without evidence of past recombination with S. dysgalactiae subsp. equisimilis or S. pyogenes.
Project description:?-Hemolytic group C and group G streptococci (GCS-GGS; Streptococcus dysgalactiae subsp. equisimilis) emerged as human pathogens in the late 1970s. We report here the draft genome sequences of four genetically distinct human strains of GCS-GGS isolated between the 1960s and 1980s. Comparative analysis of these genomes may provide a deeper understanding of GCS-GGS genome and virulence evolution.
Project description:Streptokinases secreted by nonhuman isolates of group C streptococci (Streptococcus equi, S. equisimilis, and S. zooepidemicus) have been shown to bind to different mammalian plasminogens but exhibit preferential plasminogen activity. The streptokinase genes from S. equisimilis strains which activated either equine or porcine plasminogen were cloned, sequenced, and expressed in Escherichia coli. The streptokinase secreted by the equine isolate had little similarity to any known streptokinases secreted by either human or porcine isolates. The streptokinase secreted by the porcine isolate had limited structural and functional similarities to streptokinases secreted by human isolates. Plasminogen activation studies with immobilized (His)(6)-tagged recombinant streptokinases indicated that these recombinant streptokinases interacted with plasminogen in a manner similar to that observed when streptokinase and plasminogen interact in the fluid phase. Analysis of the cleavage products of the streptokinase-plasminogen interaction indicated that human, equine, and porcine plasminogens were all cleaved at the same highly conserved site. The site at which streptokinase was cleaved to form altered streptokinase (Sk*) was also determined. This study confirmed not only the presence of streptokinases in nonhuman S. equisimilis isolates but also that these proteins belong to a family of plasminogen activators more diverse than previously thought.
Project description:Streptococcus equi (Streptococcus equi subsp. equi), a Lancefield group C streptococcus, causes strangles, a highly contagious purulent lymphadenitis and pharyngitis of members of the family Equidae. The antiphagocytic 58-kDa M-like protein SeM is a major virulence factor and protective antigen. The amino acid sequence and structure of SeM has been determined and compared to that of a second, 40-kDa M-like protein (SzPSe) of S. equi and to those of other streptococcal proteins. Both SeM and SzPSe are mainly alpha-helical fibrillar molecules with no homology other than that between their signal and membrane anchor sequences and are only distantly related to other streptococcal M and M-like proteins. The sequence of SzPSe indicates that it is an allele of SzP that encodes the variable protective M-like and typing antigens of S. zooepidemicus (S. equi subsp. zooepidemicus). SeM is opsonogenic for S. equi but not for the closely related S. zooepidemicus, whereas SzPSe is strongly opsonogenic for S. zooepidemicus but not for S. equi. Both proteins bind equine fibrinogen. SeM and SzPSe proteins from temporally and geographically separated isolates of S. equi are identical in size. The results taken together support previous evidence that S. equi is a clonal pathogen originating from an ancestral strain of S. zooepidemicus. We postulate that acquisition of SeM synthesis was a key element in the success of the clone because of its effect in enhancing resistance to phagocytosis and because protective immunity entails a requirement for SeM-specific antibody.
Project description:Vellore, a region in southern India, has a high incidence of severe human infections with Beta-hemolytic group C and G streptococci (GCGS). To determine the causative species in these infections, we conducted 16S rRNA gene sequencing: Streptococcus dysgalactiae subsp. equisimilis (81%) and S. anginosus (19%) were the causative organisms in the 2-year study period (2006-2007). We used PCR to detect the virulence-related emm gene; results showed that it was restricted to S. dysgalactieae subsp. equisimilis isolates of 99.2% tested positive. Due to a novel marker, S. anginosus and S. constellatus can be quickly and accurately distinguished from other members of the genus. The notable contribution of the anginosus group to human infections suggests that this group of obligate pathogens deserves more attention in healthcare and research.