Epidemiological shifts in and impact of COVID-19 on streptococcal toxic shock syndrome in Japan: A genotypic analysis of group A Streptococcus isolates.

OBJECTIVES: Streptococcal toxic shock syndrome (STSS) is caused by group A Streptococcus (GAS; Streptococcus pyogenes) strains. In Japan, the number of STSS cases has decreased; however, the underlying reason remains unclear. Moreover, information on distribution and prevalence of specific emm types in STSS cases is scarce. Hence, we investigated the reason for the decreased number of STSS cases in Japan. METHODS: We genotyped emm of 526 GAS isolates obtained from 526 patients with STSS between 2019 and 2022. The distributions of emm types in each year were compared. RESULTS: The emm1 type was predominant, with the highest proportion in 2019, which decreased after 2020 following the onset of the coronavirus disease 2019 (COVID-19) pandemic. Strains isolated during the pandemic correlated with strains associated with skin infection, whereas those isolated during the prepandemic period correlated with strains associated with both throat and skin infections. The decrease in the annual number of STSS cases during the COVID-19 pandemic could be due to a decreased proportion of strains associated with pharyngeal infections. CONCLUSIONS: Potential associations between pandemic and STSS numbers with respect to public health measures, such as wearing masks and changes in healthcare-seeking behavior, may have affected the number of GAS-induced infections.

Serotype Distribution and Antimicrobial Resistance of Streptococcus agalactiae Isolates in Nonpregnant Adults with Streptococcal Toxic Shock Syndrome in Japan in 2014 to 2021.

The incidence of streptococcal toxic shock syndrome (STSS) due to group B Streptococcus (GBS) has been increasing annually in Japan and is becoming a serious challenge. Furthermore, in recent years, penicillin- or clindamycin-resistant strains used in treating streptococcal toxic shock syndrome have been reported. However, no report analyzed >100 isolates of group B Streptococcus causing streptococcal toxic shock syndrome. Therefore, we aimed to perform serotyping and antimicrobial susceptibility testing of 268 isolated group B Streptococcus strains from streptococcal toxic shock syndrome cases involving nonpregnant adult patients in Japan between 2014 and 2021. The most prevalent serotype was Ib, followed by serotypes V, III, and Ia. Seven isolates were resistant to penicillin G, and 17.9% (48 isolates) were resistant to clindamycin. Of the penicillin-resistant group B Streptococcus isolates, 71.4% (5 isolates) were clindamycin resistant. In addition, group B Streptococcus strains resistant to penicillin and clindamycin were isolated from patients with streptococcal toxic shock syndrome. Therefore, before these strains become prevalent, introduction of the group B Streptococcus vaccine is essential for disease prevention. IMPORTANCE Group B Streptococcus (GBS) has been increasingly associated with invasive disease in nonpregnant adults. Such infections are responsible for substantial morbidity and mortality, particularly in individuals with underlying chronic conditions. Streptococcal toxic shock syndrome (STSS) is a severe invasive infection characterized by the sudden onset of shock, multiorgan failure, and high mortality. In this study, we assessed 268 GBS-related STSS cases in nonpregnant adults in Japan between 2014 and 2021. Serotype Ib was the most prevalent, followed by serotypes V, III, and Ia, which were identified in more than 80% of STSS isolates. We found that 48 clindamycin-resistant strains and 7 penicillin G-resistant strains were isolated between 2014 and 2021. We believe that our study makes a significant contribution to the literature because we show that the GBS vaccine, particularly the hexavalent conjugate vaccine, is important to reduce the number of patients with STSS.

Natural mutation in the regulatory gene (srrG) influences virulence-associated genes and enhances invasiveness in Streptococcus dysgalactiae subsp. equisimilis strains isolated from cases of streptococcal toxic shock syndrome.

BACKGROUND: Streptococcus dysgalactiae subspecies equisimilis (SDSE) has emerged as an important cause of severe invasive infections including streptococcal toxic shock syndrome (STSS). The present study aimed to identify genes involved in differences in invasiveness between STSS and non-invasive SDSE isolates. METHODS: STSS and non-invasive SDSE isolates were analysed to identify csrS/csrR mutations, followed by a comparative analysis of genomic sequences to identify mutations in other genes. Mutant strains were generated to examine changes in gene expression profiles and altered pathogenicity in mice. FINDINGS: Of the 79 STSS-SDSE clinical isolates, 15 (19.0%) harboured csrS/csrR mutations, while none were found in the non-invasive SDSE isolates. We identified a small RNA (sRNA) that comprised three direct repeats along with an inverted repeat and was transcribed in the same direction as the sagA gene. The sRNA was referred to as srrG (streptolysin S regulatory RNA in GGS). srrG mutations were identified in the STSS-SDSE strains and were found to be associated with elevated expression of the streptolysin S (SLS) gene cluster and enhanced pathogenicity in mice. INTERPRETATION: The csrS/csrR and srrG mutations that increased virulence gene expression in STSS-SDSE isolates were identified, and strains carrying these mutations caused increased lethality in mice. A significantly higher frequency of mutations was observed in STSS-SDSE isolates, thereby highlighting their importance in STSS. FUNDING: Japan Agency for Medical Research and Development, the Japan Society for the Promotion of Science (JSPS), and the Ministry of Health, Labor, and Welfare of Japan.

Molecular characterization and antimicrobial resistance of group A streptococcus isolates in streptococcal toxic shock syndrome cases in Japan from 2013 to 2018.

Streptococcal toxic shock syndrome (STSS) is a severe invasive infection characterized by the sudden onset of shock, multi-organ failure, and puerperal sepsis and shows high mortality. Its primary cause is group A streptococcus (GAS, Streptococcus pyogenes). In this study, we genotyped the cell-surface M virulence protein gene (emm) from 621 GAS isolates obtained from patients with STSS in Japan in 2013-2018 and performed antimicrobial susceptibility testing using the broth microdilution method. The predominant emm type was found to be 1, followed by 89, 12, and 3, which were identified in more than 70 % of STSS isolates. The proportions of emm3 and emm89 increased from 2.4 % and 12.0 %, respectively, during 2010-2012 to 5.6 % and 23.3 % during 2013-2018. In contrast, the proportion of emm1 decreased from 60.6 % to 39.3 % during the same two periods. Some emm types showed increasing proportions and were not isolated from patients with STSS in 2010-2012. Among these, an emm76 type increased in prevalence and was not included in the 30-valent M protein-based vaccine. Continual investigation of changes in the epidemiology of GAS which causes STSS can provide useful monitoring information such as future vaccination strategies and the emergence status of antimicrobial-resistant bacteria.

T serotyping of group a streptococcus isolated from patients with pharyngitis or streptococcal toxic shock syndrome in Japan between 2005 and 2017.

Streptococcus pyogenes (group A streptococcus; GAS) is an important gram-positive human pathogen capable of causing diseases ranging from mild superficial skin and pharyngeal infections to more severe invasive diseases, including streptococcal toxic shock syndrome (STSS). GAS produces a T protein, and T serotyping has considerable discriminatory power for epidemiological characterization of GAS. To clarify the relationship between STSS and pharyngitis in Japan, we examined the T serotypes of GAS strains isolated from clinical specimens of streptococcal infections (STSS, 951 isolates; pharyngitis, 16268 isolates) from 2005 to 2017. The most prevalent T serotype from pharyngitis isolates was T12, followed by T1, T4, and TB3264. The most prevalent T serotype from STSS isolates was T1, followed by TB3264. Trend of increase and decrease in the frequency of T1 or TB3264 isolation from pharyngitis was correlated with that of STSS patients. The increase of T1 or TB3264 strain-infection in pharyngitis patients may increase the probability of causing STSS, indicating that careful monitoring of GAS serotypes is essential for the prediction of rapid increase of STSS in time to develop effective management strategies.

Genetic Characterization of Streptococcus pyogenes emm89 Strains Isolated in Japan From 2011 to 2019.

Invasive infection caused by Streptococcus pyogenes emm89 strains has been increasing in several countries linked to a recently emergent clade of emm89 strains, designated clade 3. In Japan, the features of emm89 S. pyogenes strains, such as clade classification, remains unknown. In this study, we collected emm89 strains isolated from both streptococcal toxic shock syndrome (STSS) (89 STSS isolates) and noninvasive infections (72 non-STSS isolates) in Japan from 2011 to 2019, and conducted whole-genome sequencing and comparative analysis, which resulted in classification of a large majority into clade 3 regardless of disease severity. In addition, invasive disease-associated factors were found among emm89 strains, including mutations of control of virulence sensor, and absence of the hylP1 gene encoding hyaluronidase. These findings provide new insights into genetic features of emm89 strains.

Detection of pathogenic Yersinia enterocolitica in pet Djungarian hamsters in Japan.

The prevalence of Yersinia enterocolitica (Y. enterocolitica) and Yersinia pseudotuberculosis was examined in 151 pet animals including 108 rodents, 39 rabbits and four sugar gliders from 13 pet stores in the Yamaguchi Prefecture, Japan. Y. enterocolitica serogroup O:3 biotype 3 negative for the Voges-Proskauer reaction (O:3/3 variant VP-) was isolated from five Djungarian hamsters (Phodopus sungorus) raised at the same pet store. These pathogenic Y. enterocolitica isolates carried the virulence genes, yadA, ail and virF, and were shown to be clonal by pulsed-field gel electrophoresis with NotI digestion. This is a first report of pathogenic Y. enterocolitica O:3/3 variant VP- in pet Djungarian hamsters in Japan.