Molecular epidemiologic and clinical analysis of Helicobacter cinaedi bacteremia in Japan

Helicobacter cinaedi is an important pathogen that causes bloodstream infections. Owing to the challenges in its culture and identification, its clinical and bacterial characteristics remain unknown. Our study aimed to investigate the molecular epidemiology and antimicrobial susceptibility of H cinaedi.

From 2003 to 2016, we analyzed 16 non-repetitive H cinaedi strains, isolated from blood, at the medical hospital of Tokyo Medical and Dental University. Multilocus sequence typing was performed to analyze the genetic relationship across the different isolates. The minimum inhibitory concentrations (MIC) of antibiotics were determined by the agar dilution method.

The median age of subjects in this study was 61 years (range, 18-84 years). The most common risk factors included the use of steroids (75.0%) and immunosuppressant drugs (37.5%). In addition, the most common symptoms of H cinaedi bacteremia included colitis (37.5%) and cellulitis (31.3%). The infection recurred in three of seven cases (42.8%) that underwent antibiotic therapy for <10 days. The strains were classified into five sequence types (ST), of which, ST 10 (43.8%) and ST 4 (31.3%) were predominant. The MIC₉₀ values of amoxicillin, gentamycin, imipenem, ciprofloxacin, and clarithromycin were 4, 0.5, 0.25, 64, and 128 mg/L, respectively.

Since there is no recommended guideline yet for the choice or duration of antibiotic therapy and antimicrobial break points, our results suggested, for the first time, that prolonged antibiotic therapy, except with ciprofloxacin and clarithromycin, would be required to ensure resolution of symptoms and prevention of recurrence.