We report 21 cases of M. haemophilum infection over a 6-year period at the largest academic hospital in Thailand. M. haemophilum commonly causes infection in immunocompromised persons. Advanced HIV infection remains the most common immunocompromised condition associated with this infection, as reported.[1,3] Approximately 60% of patients have skin and soft tissue involvement, and the most commonly involved areas are the extensor surfaces of the extremities and auricular regions, which could be explained by the predilection of the organism for body areas with lower temperatures.
Although CNS infection with M. haemophilum is extremely rare and only a few case-patients have been reported,[11–13] we identified CNS involvement in 3 of 21 case-patients in our study. All had advanced HIV disease: 2 patients had multiple brain abscesses, which was similar to those previously described, and 1 patient had myelitis. A total of 2 of 3 previous case reports of CNS involvement in patients with M. haemophilum infection were from Thailand and in HIV-infected patients,[11,12] whereas the 2 largest case series (23 and 15 cases) reported from the United States found no cases of CNS involvement.[3,4] Further study is needed to determine whether genetic or environmental factors will influence clinical manifestations of M. haemophilum infection.
Treatment with a combination of fluoroquinolones, rifampin, and macrolides is suggested for treating M. haemophilum infection. However, our study demonstrated that 2 antimycobacterial agents (macrolides and fluoroquinolones) were successfully used for patients with isolated cutaneous diseases. Conversely, surgical resection might be needed for some case-patients, such as those who showed treatment failure or those in which there was CNS involvement. Because of poor penetration of the CNS by these antimicrobial agents, patients who had mycobacterial infections with CNS involvement are often associated with poorer outcomes.[15,16] Two previous case reports of persons with CNS disease were successfully treated with surgical excision in combination with antimicrobial drugs, although there were residual neurologic deficits.[11,13] Another study reported a case-patient who did not respond to medical therapy alone and subsequently died.
Treatment for M. haemophilum infection should last ≈3–12 months and should be tailored on the basis of severity of disease and immunocompromised conditions. Isolated cutaneous disease usually responds well to shorter duration of therapy (3–6 months), and CNS infections, bone and joint infections, and disseminated disease usually require longer therapy (12 months). Relapse cases have been rarely reported, and accounted for just 4% in the largest case series. However, our study showed a higher relapse rate (14%); therefore, we suggest that careful monitoring after discontinuation of treatment is warranted.
One limitation of our study was that no antimicrobial susceptibility testing was available because all culture-positive cases were detected in liquid medium. However, no data support the correlation of in vitro susceptibility testing and treatment response for this type of infection.
M. haemophilum infections should be suspected in immunocompromised patients who have unexplained cutaneous lesions, especially at auricular or extensor surfaces of extremities, who are smear positive for acid-fast bacilli, but show negative results for routine mycobacterial culture. Combination antimycobacterial therapy should be given for ≥3 months and extended to 12 months depending on the site of isolation. CNS involvement might occur more commonly than previously believed and is associated with worse outcome. Relapses are not uncommon; therefore, clinical monitoring after discontinuation of treatment is warranted.
We thank all medical staff and laboratory technicians who were involved in the study and those who cared for the patients.
Emerging Infectious Diseases. 2019;25(9):1648-1652. © 2019 Centers for Disease Control and Prevention (CDC)