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Streptococcus pyogenes is a causative agent of streptococcal toxic shock syndrome (STSS). The complete genome sequence of a S. pyogenes strain 10-85 isolated from a STSS patient was recently announced. In this study, the genome sequence was dissected and it was found that the genomic region around 200 kbp (region A) and the genomic region around 1600 kbp (region B) were replaced by each other in strain 10-85, when compared with those in reference strains SF370 and A20. In order to address whether this replacement is unique to 10-85, we further analyzed 163 emm1-type strains. The results indicated that none of the strains isolated before 1990 had the replacement. In contrast, most of the strains isolated at least after 2000 appeared to have the 10-85-type replacement., (© 2019 The Societies and John Wiley & Sons Australia, Ltd.)

Streptococcal toxic shock syndrome (STSS) is primarily caused by Streptococcus pyogenes, but it may also be caused by Streptococcus dysgalactiae subsp. equisimilis (SDSE). The analyses of S. pyogenes have revealed the important roles of NAD + -glycohydrolase (Nga) and CovR/CovS, a two-component regulatory system. We examined these factors in SDSE by analyzing mainly two isogenic SDSE strains (12-10-1 and 12-10-3) from the blood of a patient with STSS. The Nga activities were measured and the nucleotide sequences of covR and covS genes were determined. We detected one nucleotide difference between the covR gene of 12-10-1 and that of 12-10-3, and the Nga activity of 12-10-1 was approximately 6.8-fold more than that of 12-10-3. The introduction of covR of 12-10-3 into 12-10-1 significantly reduced the Nga activity, but the introduction of 12-10-1 covR into itself had only a little effect. In addition, the knockout of covR or covS of 12-10-3 remarkably increased the Nga activity. We are the first to report that strains with wild-type and mutated covR were isolated simultaneously from an SDSE STSS patient and that the CovR/CovS two-component regulatory system is involved in the Nga activity in SDSE as well as in S. pyogenes., (© 2019 APMIS. Published by John Wiley & Sons Ltd.)

We identified hypervirulent Streptococcus pyogenes in 27 and 420 isolates from patients with invasive and non-invasive diseases, respectively, in Aichi Prefecture, Japan, between 2003 and 2012, in an attempt to understand why the prevalence of streptococcal toxic shock syndrome (STSS) suddenly increased in this location during 2011. Hypervirulent strains belong to the emm1 genotype, with a mutation in the covR/S genes that regulate many other genes, encoding virulence determinants and resulting in the absence of the proteinase streptococcal exotoxin B and the production of virulence factors such as the superantigen streptococcal exotoxin A, the nuclease streptococcal DNase, the cytotoxin NAD-glycohydrolase, and the hemolysin streptolysin O. We found 1 strain from invasive disease and 1 from non-invasive disease with traits similar to those of hypervirulent strains, except that the sda1 gene was absent. We also found 1 non-emm1 strain with phenotypic and genetic traits identical to those of the emm1 hypervirulent strains except that it did not belong to emm1 genotype, from non-invasive diseases cases in 2011. These findings suggested that hypervirulent and hypervirulent-like strains from invasive and non-invasive disease cases could have at least partially contributed to the sudden increase in the number of patients with STSS in Aichi during 2011.

Streptococcus pyogenes is a causative agent of streptococcal toxic shock syndrome (STSS). Mutations in covR/S or rgg, negative regulators, can reportedly modulate the severity of infection in this pathogen. Recently, we showed that the regions encoding the SalR-SalK, a two-component regulatory system, were deleted in some emm 1-type isolates (named as 'novel-type'). In this study, the two novel 'STSS' isolates 10-85stss and 11-171stss were more virulent than the two novel 'non-STSS' isolates 11O-2non and 11T-3non when examined using a mouse model of invasive infection. Genome-sequencing experiments using the three strains 10-85stss , 11-171stss , and 11O-2non detected only one single nucleotide polymorphism that causes a non-synonymous mutation in fabT encoding a transcriptional regulator in strain 11O-2non . Loss of fabT reduced the high level of virulence observed in the STSS isolates to that in the non-STSS isolates, and introduction of an intact fabT compensated the lower virulence of 11O-2non , suggesting that the mutation in fabT, but not in covR/S or rgg, is involved in the differential virulence among the novel-type clinical isolates. This type of non-synonymous fabT mutation was also identified in 12 non-STSS isolates (including 11O-2non and 11T-3non ), and most of those 12 isolates showed impaired FabT function., (© 2016 APMIS. Published by John Wiley & Sons Ltd.)

In Japan, the number of patients with streptococcal toxic shock syndrome is reported to be increasing. mef(A) gene-positive macrolide-resistant emm1 strains are thought to possibly contribute to the rise in the frequency of STSS. Although analyses of macrolide-resistant mechanisms, including mef(A) resistance, have been performed mainly in Streptococcus pneumoniae, the role of this gene in Streptococcus pyogenes has not been completely investigated. Therefore, to the best of our knowledge, we established the first mef(A)-knockout strain using an emm1-type S. pyogenes strain, and tested its susceptibility to erythromycin, clarithromycin and azithromycin. We found that the antimicrobial susceptibilities were almost identical to those of the parental strain. Hence, we established a knockout strain for another gene, msr(D), that is located immediately downstream of mef(A). The macrolide resistances of the resulting strain significantly decreased, and were further altered when both mef(A) and msr(D) were knocked out. The introduction of the msr(D) gene into a macrolide-sensitive strain conferred more resistance than the introduction of the mef(A) gene. The erythromycin susceptibilities of knockout strains were further dissected using two additional emm4- and emm75-type S. pyogenes strains. We found almost identical results for both strains except for the mef(A) knockout emm4 type, whose susceptibility was altered, although the change was less than that for the msr(D) knockout. These results suggest that both mef(A) and msr(D) are involved in macrolide resistance in S. pyogenes, and that the msr(D) gene plays a more predominant role in macrolide resistance than mef(A).

Streptococcus pyogenes is indigenous to the human pharynx and causes acute pharyngitis. Balanoposthitis is an inflammatory disease of the glans and the foreskin. However, balanoposthitis caused by S. pyogenes is not widely recognized as a sexually transmitted disease. In addition, bacteriological features of the isolates causing balanoposthitis are unclear. The four S. pyogenes strains isolated from adult balanoposthitis were examined. We performed emm typing, T antigen typing, RAPD assay, PCR assay for the streptococcal pyrogenic exotoxin-related genes and antibiotic-resistant genes, and antibiotic susceptibility assay. All four strains were suspected to be transmitted by penile-oral sexual intercourse, were found to be different by genetic analysis, and also harbored some antibiotic-resistant factors. We propose that S. pyogenes should be considered as a causative agent of sexually transmitted disease. The drug resistant S. pyogenes must be taken into account when balanoposthitis patients are treated with antibiotic.

Thirteen Streptococcus dysgalactiae subsp. equisimilis isolates possessing Lancefield's group A antigen recovered from people in Japan during 2000 to 2004 were genotyped. The results indicate that a conserved clone has persisted and spread within Japan, and two different emm types were observed within members of this clone.

Selection of new variants of the streptococcal inhibitor of complement protein has been implicated in the perpetuation of epidemics caused by serotype M1 strains of group A Streptococcus (GAS). The frequency at which new streptococcal inhibitor of complement (Sic) variants arise in an infected individual is not known. To study this issue, the sic gene was sequenced in 100 isolates cultured from throat swabs of each of 20 patients with acute pharyngitis caused by serotype M1 GAS. Five patients were infected with GAS populations expressing 2 Sic variants characterized by deletion of a region of the protein. In contrast, no intrahost variation was detected in the number of a pentanucleotide repeat (CAAAA) that controls production of a bacterial cell-surface collagen-like protein by slipped-strand mispairing. Sic variation occurs at a sufficient frequency in vivo to result in mixed infections on the mucosal surface of human hosts, potentially contributing to pathogen survival.