VapB-positive Rhodococcus equi infection in an HIV-infected patient in Japan

Rhodococcus equi, a bacterium present in soil, is a common cause of pneumonia in foals. This organism has been recognized as an opportunistic pathogen in humans, typically causing infection in immunocompromised hosts such as HIV-infected patients and organ transplant recipients. However, human infection with R. equi has not been reported in Japan except in a case involving a laboratory worker. We report the first human case of VapB-positive R. equi pneumonia, which involved an HIV-infected patient living in an urban area in Japan. The patient was treated successfully with 450mg rifampicin and 600mg tosufloxacin, even though his CD4+ lymphocyte count at the time of diagnosis was 10/µl. The patients dogs were suspected in the epidemiology of this infection, but unfortunately we could not isolate the organism from canine-associated specimens in this case. R. equi infections in companion animals have been thought to be very rare, but they may be increasing in dogs. Therefore, further epidemiological research may clarify the prevalence of R. equi infection and the factors predisposing dogs to this infection.