Management
Although there are no standard guidelines for antibiotic treatment of M haemophilum, the current literature recommends triple-drug therapy with clarithromycin, ciprofloxacin, and rifamycin for at least 12 to 24 months.2
Upon clinical suspicion of an atypical Mycobacterium, we recommend a macrolide antibiotic over doxycycline, however, because this class of agents maintains broad coverage while being more specific for atypical mycobacteria. Although an atypical Mycobacterium was suspected early in the presentation in our cases, we discourage immediate use of triple-agent antibiotic therapy until laboratory evidence is procured to minimize antibiotic overuse in patients who do not have a final diagnosis. Single-agent therapy for prolonged treatment is discouraged for atypical mycobacterial infections because of the high risk of antibiotic resistance. Therapy should be tailored to the needs of the individual based on the extent of dissemination of disease and the severity of immunosuppression.1,2
Additionally, underlying disease that results in immunosuppression might necessitate treatment reevaluation (as occurred in our cases) requiring cessation of immunosuppressive drugs, extended careful monitoring, and pharmacotherapeutic readjustment through the course of treatment. The degree to which antibiotics contribute to eradication of M haemophilum is unknown; therefore, it is recommended that long-term antibiotic use and treatment aimed at recovering the immunocompromised state (eg, highly active antiretroviral therapy in a patient with AIDS) be implemented.2
Conclusion
Our 3 cases of M haemophilum infection involved the upper extremities of immunosuppressed patients older than 65 years. This propensity to affect the upper extremities could possibly be due to the lower temperature required for growth of M haemophilum. Initial histopathologic study showed granulomatous and neutrophilic infiltrates, yet histopathologic specimens from all 3 patients failed to display positive AFB staining, which delayed the initial antibiotic choice. In all cases, diagnosis was made by tissue culture after swab culture failed to grow the pathogen. Furthermore, the 3 cases took approximately 6 weeks to achieve final identification of the organism. Neither clinical lymphadenopathy nor systemic spread was noted in our patients; immunosuppression was discontinued when possible.
Mycobacterium haemophilum is an uncommon but potentially life-threatening infection that should be suspected in immunocompromised adults who present with atypical cellulitis of the extremities. The ultimate diagnosis often is delayed because the organism grows slowly (as long as 8 weeks) in tissue culture. For that reason, empiric antibiotic treatment, including a macrolide, should be considered in patients with disseminated or severe infection or critical immunosuppression and in those who do not demonstrate improvement in symptoms once immunosuppressants are withheld. A prolonged course of multiple-drug antibiotic therapy has proved to be effective for treating cutaneous infection with M haemophilum.