Streptococcus pyogenes (group A Streptococcus; GAS) is an important human pathogen that causes non-invasive infections such as scarlet fever, pharyngitis, and impetigo, as well as severe and life-threatening conditions such as streptococcal toxic shock syndrome (STSS). Recently, a hypertoxigenic lineage of S. pyogenes, the M1_UK lineage, has emerged and spread rapidly across various countries.

In this study, we investigated the detection rate and genetic characteristics of the M1_UK lineage of S. pyogenesemm1 among strains isolated from patients with pharyngitis or STSS in Kobe, Japan, between 2016 and March 2024. Eleven M1_UK lineage strains (seven from pharyngitis cases and four from STSS cases) were identified in 2019, prior to the COVID-19 pandemic. Seven strains (five from pharyngitis cases and two from STSS cases) were detected after 2023. Whole-genome sequencing of the M1_UK lineage strains identified two distinct clades among the 2019 strains, with a different clade emerging after 2023. Haplotype network analysis based on single-nucleotide variants (SNVs) revealed that each clade included isolates from both pharyngitis and SSTS cases, differing by 0-2 SNVs.

Our findings indicate that the M1_UK lineage, which causes both pharyngitis and SSTS, has been circulating in Kobe since 2019 and has spread to Kobe. Furthermore, our data suggest that a distinct clade of the M1_UK lineage has emerged in Kobe after the COVID-19 pandemic.

A 26-year-old man from Bolivia who presented with a 1-month history of fever was referred to Gunma University Hospital. Initial tests revealed that revealed positive results for infection with human immunodeficiency virus (HIV) and chest computed tomography (CT) showed diffuse pulmonary micronodules suggestive of miliary tuberculosis. Polymerase chain reaction (PCR) and culture tests for tuberculosis yielded negative results. However, the patient was admitted to another hospital due to worsening of the respiratory symptoms, and initiated on anti-tuberculosis treatment. Despite the treatment, however, the patient's condition deteriorated and he was transferred in a state of septic shock to the intensive care unit of Gunma University Hospital. He was initiated on broad-spectrum antibiotic, antifungal, and antiretroviral therapy but failed to show improvement and died a few days later due to multiple organ failure. Postmortem examination revealed disseminated yeast-like fungi in multiple organs, including the lungs, liver, spleen, and bone marrow. Given the patient's background, we considered the possibility of imported mycosis. Using a pan-fungal PCR protocol, the causative pathogen was genetically identified as Histoplasma capsulatum. Based on this result, the patient's condition was diagnosed as disseminated histoplasmosis. This case highlights the importance of considering histoplasmosis in the differential diagnosis of patients who present with features mimicking miliary tuberculosis, particularly in those with a travel history to endemic regions.

A 24-year-old Vietnamese male patient presented with fever, cough, sore throat, and body pain. Nineteen days previously, the patient experienced nasal discharge and SARS-CoV-2 PCR at local pharmacy was positive. Based on the post COVID-19 status and symptoms, the current diagnosis was multisystem inflammatory syndrome in adults (MIS-A). Treatment with cefazolin was initiated owing to the possibility of bacterial pharyngitis; however, the symptoms did not improve. Additionally, the patient developed pericarditis. Instead of symptomatic therapy, the symptons, in fact, worsened and the patient developed pericarditis. He was then initiated on treatment with a corticosteroid (methylprednisolone 2mg/kg/day by intravenous infusion) and oral aspirin (100mg/day). With this treatment, the patient recovered and was discharged on an oral corticosteroid (prednisolone 30mg/day). We discuss this case along with a review of the literature to underscore the importance of early recognition of MIS-A and the current status of its treatment.