Mycobacterium haemophilum infection in a Japanese patient with AIDS

Case of Mycobacterium haemophilum misdiagnosed as Mycobacterium intracellulare due to one base insertion in the bacterial genome

Mycobacterium haemophilum is a slow-growing, non-tuberculous mycobacteria that causes cutaneous infection. We describe a case of cutaneous infection in a 68-year-old Japanese man with polymyositis. This was caused by M. haemophilum harboring one base insertion in gene sequence. At first, the causal microorganism was misidentified as M. intracellulare by COBAS^® TaqMan^® MAI test. However, poor growth on Ogawa media and growth enhancement on 7H11C agar around a hemin-containing disk prompted us to reinvestigate the causal microorganisms, which were revealed to be M. haemophilum. Amplified polymerase chain reaction products were sequenced, and the 16S rRNA gene, rpoB, hsp65 and internal transcribed spacer region sequences showed a 100%, 100%, 99.66% and 99.7% match, respectively, with the corresponding regions of M. haemophilum, but it harbored a novel gene sequence in hsp65. The sequences determined by gene analysis of the M. haemophilum strain were deposited into the International Nucleotide Sequence Database. Although numerous cases of M. haemophilum infection have been reported in other countries, only six cases have been reported in Japan to date. It could be possible that this novel mutation lead to misdiagnosis. As M. haemophilum prefers a lower growth temperature (30-32°C) and it requires iron in the culture medium, M. haemophilum could be misidentified or overlooked. Accordingly, a M. haemophilum infection should be considered in cases of cutaneous infection of the body sites, of which surface temperature is low.

Clinical manifestations, diagnosis, and treatment of Mycobacterium haemophilum infections

Mycobacterium haemophilum is a slowly growing acid-fast bacillus (AFB) belonging to the group of nontuberculous mycobacteria (NTM) frequently found in environmental habitats, which can colonize and occasionally infect humans and animals. Several findings suggest that water reservoirs are a likely source of M. haemophilum infections. M. haemophilum causes mainly ulcerating skin infections and arthritis in persons who are severely immunocompromised. Disseminated and pulmonary infections occasionally occur. The second at-risk group is otherwise healthy children, who typically develop cervical and perihilar lymphadenitis. A full diagnostic regimen for the optimal detection of M. haemophilum includes acid-fast staining, culturing at two temperatures with iron-supplemented media, and molecular detection. The most preferable molecular assay is a real-time PCR targeting an M. haemophilum-specific internal transcribed spacer (ITS), but another approach is the application of a generic PCR for a mycobacterium-specific fragment with subsequent sequencing to identify M. haemophilum. No standard treatment guidelines are available, but published literature agrees that immunocompromised patients should be treated with multiple antibiotics, tailored to the disease presentation and underlying degree of immune suppression. The outcome of M. haemophilum cervicofacial lymphadenitis in immunocompetent patients favors surgical intervention rather than antibiotic treatment.