Mycobacterium celatum infection in two HIV-infected patients treated prophylactically with rifabutin

Mycobacterium celatum is a recently described slow-growing species. It was identified on the basis of genomic sequencing that differentiates three types. The present report describes two cases of Mycobacterium celatum type 1 infection in patients with AIDS. Both patients had CD4+ lymphocyte counts of < 10/mm3, were receiving rifabutin prophylaxis, and had attended the same treatment units. The minimum inhibitory concentration of rifabutin for both strains was 8 mg/l, which may account for the failure of prophylaxis. As all type 1 strains have the same pulsed-field gel electrophoresis pattern, nosocomial transmission or acquisition from a common source could not be ruled out.