Multicenter study to evaluate bloodstream infection by Helicobacter cinaedi in Japan.

Helicobacter cinaedi has being recognized as an important human pathogen which causes bloodstream infections. Although the first case of bacteremia with this pathogen in Japan was reported in 2003, the true prevalence of H. cinaedi as a pathogen of bloodstream infections in this country is not yet known. Therefore, the aim of our study was to assess the incidence of bacteremia with H. cinaedi in Japan. We conducted a prospective, multicenter analysis in 13 hospitals during 6 months in Tokyo, Japan. Among positive blood cultures from 1 October 2003 to 31 March 2004, isolates suspected of being Helicobacter species were studied for further microbial identification. Identification of the organisms was based on their biochemical traits and the results of molecular analysis of their 16S rRNA gene sequences. A total of 16,743 blood culture samples were obtained during the study period, and 2,718 samples (17.7%) yielded positive culture results for coagulase-negative staphylococci. Among nine isolates suspected to be Helicobacter species, six isolates were finally identified as H. cinaedi. The positivity rate for H. cinaedi in blood culture was 0.06% of total blood samples and 0.22% of blood samples with any positive culture results. All patients with bacteremia with H. cinaedi were found to have no human immunodeficiency virus (HIV) infection, but many of them had complications with either malignancy, renal failure, or a history of surgical operation. Therefore, our results suggest that bacteremia with H. cinaedi is rare but can occur in compromised hosts other than those with HIV infection in Japan.