The diagnosis of two cases of cutaneous ulcer caused by infection with Mycobacterium haemophilum: direct identification in a clinical sample by polymerase chain reaction-restriction endonuclease analysis.

BACKGROUND

Mycobacterium haemophilum was first recovered from subcutaneous lesions of a patient with Hodgkin's disease. Because of its special growth requirements (it grows at 30-32 degrees C and requires iron-supplemented medium), the organism cannot be isolated using routine culture techniques for other mycobacteria. Only a few developed countries have reported infection with this mycobacterium. We report the first two cases diagnosed in Venezuela.

METHODS

The diagnosis of the first case was established using polymerase chain reaction (PCR)-restriction endonuclease analysis of the gene encoding the 65-kDa heat shock protein (hsp65) for the direct identification of M. haemophilum in a clinical specimen in which bacilli were observed on acid-fast smear, but growth was not detected by standard culture procedures.

RESULTS

After recognizing this bacterium as a possible cause of infection in our setting, clinical samples of cutaneous lesions were routinely cultured on blood agar at 30 degrees C for at least 6 weeks, which resulted in the diagnosis of the second case.

CONCLUSIONS

Dermatologists should consider this bacterium in immunocompromised patients with cutaneous ulcerating lesions. Material from the lesions can be screened for mycobacteria using an acid-fast stain and, if acid-fast bacilli are seen, PCR analysis of mycobacterial hsp65 can be an effective tool for early diagnosis. Appropriate culture methods are required for bacteriologic confirmation of infection with M. haemophilum.