Clinical and epidemiologic characteristics of Mycobacterium haemophilum, an emerging pathogen in immunocompromised patients.

<bold>Objective: </bold>To describe 13 infections caused by Mycobacterium haemophilum.<bold>Design: </bold>Identification of patients by microbiologic record review, followed by medical record review and a case-control study.<bold>Setting: </bold>Seven metropolitan hospitals in New York.<bold>Patients: </bold>All patients with M. haemophilum infections diagnosed between January 1989 and September 1991 and followed through September 1992. Surviving patients were enrolled in the case-control study.<bold>Results: </bold>Infection with M. haemophilum causes disseminated cutaneous lesions, bacteremia, and diseases of the bones, joints, lymphatics, and the lungs. Improper culture techniques may delay laboratory diagnosis, and isolates may be identified incorrectly as other mycobacterial species. Persons with profound deficits in cell-mediated immunity have an increased risk for infection. These include persons with human immunodeficiency virus infection or lymphoma and those receiving medication to treat immunosuppression after organ transplant. Various antimycobacterial regimens have been used with apparent success to treat M. haemophilum infection. However, standards for defining antimicrobial susceptibility to the organism do not exist.<bold>Conclusions: </bold>Clinicians should consider this pathogen when evaluating an immunocompromised patient with cutaneous ulcerating lesions, joint effusions, or osteomyelitis. Microbiologists must be familiar with the fastidious growth requirements of this organism and screen appropriate specimens for mycobacteria using an acid-fast stain. If acid-fast bacilli are seen, M. haemophilum should be considered as the infecting organism as well as other mycobacteria, and appropriate media and incubation conditions should be used. [ABSTRACT FROM AUTHOR]