First case of bloodstream infection caused by Cupriavidus metallidurans in Japan.

We report the first case in Japan of a bloodstream infection caused by Cupriavidus metallidurans. The patient was a 77 years old man hospitalized for treatment of heart failure and diabetes. On day 83 of hospitalization, he developed a fever of 38.0°C, followed three days later by an elevation in C-reactive protein. His condition improved with the administration of cefmetazole, cefepime, and levofloxacin, and antibiotic therapy was discontinued on the 17th day after the onset of fever. Blood cultures collected at the onset of fever revealed growth in the aerobic bottle after 21 h, and Gram staining revealed slightly slender Gram-negative rods. Based on colony morphology, Burkholderia or Ralstonia was initially suspected. However, identification kit ID Test NF-18 yielded multiple possible organisms, and a definitive identification could not be made. The isolate was ultimately identified as C. metallidurans by phylogenetic analysis of the 16S rRNA gene. Because this species is not included in general bacterial identification kits and cannot be reliably distinguished based biochemical characteristics alone, 16S rRNA gene sequencing was essential for diagnosis. To date, only five cases of bloodstream infection caused by this species have been reported, in Canada and Italy, and this is the first reported case in Japan. As this bacterium is present in the Japanese environment, reports of its detection may increase in the future, particularly among elderly or immunocompromised patients.