This study examined temporal trend, seasonality, and geographical variations of legionellosis incidence and mortality in Japan. This nationwide observational study used the Japanese Vital Statistics and Infectious Diseases Weekly Report (1999–2017) data to calculate legionellosis crude and age-adjusted incidence and mortality rates per 100,000 population by age and sex. Incidence was compared among the 4 seasons and regional incidence among 47 prefectures. Of 13,613 (11,194 men) people with legionellosis in Japan, 725 (569 men) were fatal. Increasing incidence trend occurred from 0.0004 (1999) to 1.37 (2017) per 100,000 population. People aged ≥ 70 years accounted for 43.1% overall; men’s age-adjusted incidence rate was consistently approximately five times higher than for women. Significantly higher incidence occurred in summer than in winter (p = 0.013). Geographically, highest incidence (≥ 2.0 per 100,000 population) occurred in Hokuriku District, with increasing trends in Hokkaido and middle-part of Japan. Estimated fatality rates decreased consistently at 5.9% (95% confidence interval: − 8.1, − 3.5) annually, from 1999 to 2017, with no trend change point. Increasing legionellosis incidence occurred in Japan during 1999–2017, with declining estimated fatality rates. In this aging society and warming world, disease clinical burden may further deteriorate in future due to increasing incidence trends.

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Campylobacter species are the pathogens of the intestinal tract, which infrequently cause bacteremia. To reveal the clinical characteristics of Campylobacter bacteremia, we performed a retrospective, multicenter study. Patients diagnosed with Campylobacter bacteremia in three general hospitals in western Japan between 2011 and 2021 were included in the study. Clinical, microbiological, and prognostic data of the patients were obtained from medical records. We stratified the cases into the gastroenteritis (GE) and fever predominant (FP) types by focusing on the presence of gastrointestinal symptoms. Thirty-nine patients (24 men and 15 women) were included, with a median age of 57 years and bimodal distribution between those in their 20 s and the elderly. The proportion of GE and FP types were 21 (53.8%) and 18 (46.2%), respectively. Comparing these two groups, there was no significant difference in patient backgrounds in terms of sex, age, and underlying diseases. Campylobacter jejuni was exclusively identified in the GE type (19 cases, 90.5%), although other species such as Campylobacter fetus and Campylobacter coli were isolated in the FP type as well. Patients with the FP type underwent intravenous antibiotic therapy more frequently (47.6% vs. 88.9%), and their treatment (median: 5 days vs. 13 days) and hospitalization (median: 7 days vs. 21 days) periods were significantly longer. None of the patients died during the hospitalization. In summary, we found that nearly half of the patients with Campylobacter bacteremia presented with fever as a predominant manifestation without gastroenteritis symptoms.

Odontogenic infections, generally caused by dental caries and periodontal disease, can result in fatal illness. We herein report a 71-year-old Japanese woman with type 2 diabetes and hemodialysis who suffered from multiple dentofacial abscesses mainly caused by multidrug-resistant Streptococcus oralis. She complained of pain and swelling of her face, with an extraoral fistula from the left cheek. Following 3 surgical debridement procedures and partial mandibulectomy, in addition to 12 weeks of antimicrobial therapy, the multiple dentofacial abscesses were ameliorated. A combination of surgical and antimicrobial treatments following an early diagnosis is essential for reducing further complications.