With the expansion of the immunocompromised patient population, infections due to nontuberculous mycobacteria (NTM) are increasing in frequency1, and their impact is significant as they may produce considerable patient morbidity. As a result, more familiarity with these organisms and the infections that they may produce is required. There are currently more than 150 species of NTM that are divided into rapidly, intermediate and slowly growing species2.
Rapidly growing mycobacteria produce mature colonies on solid media within 7 days. There are about 20 species of rapidly growing NTM that are capable of infecting human beings3. Of interest among the rapidly growing NTM, are two less commonly isolated mycobacteria, Mycobacterium mucogenicum and Mycobacterium neoaurum. They are ubiquitous in the environment, including household water, potting soil, animals, birds and vegetables. These organisms have been increasingly noted to be the cause of significant infections in immunocompromised hosts.
The current literature highlights that the most common infection caused by M. mucogenicum and M. neoarum is catheter-related bloodstream infection (CRBSI)4–7. The frequent use of indwelling intravascular catheters in immunocompromised individuals has been accompanied by NTM CRBSI, especially in patients with underlying malignancies9.
These organisms have the ability to form a protective biofilm, which plays a role in CRBSI. Biofilms in turn confer decreased penetration to antimicrobials, enhance the potential of resistance and are integral to device-related infections9. These organisms are also able to tolerate disinfectants, chlorination and extreme temperatures.
M. mucogenicum and M. neoaurum infections are seen more often in long-term central intravenous catheters causing catheter-related sepsis, but they may also occur with peritoneal or shunt catheters. Central nervous system infections involving Mycobacterium mucogenicum are rare but serious, particularly for immunocompromised patients resulting in meningitis due to this organism5. Skin and soft tissue infections caused by these organisms have also been reported4,10.
In immunocompromised patients, M. mucogenicum or M. neoaurum isolated from the bloodstream should be considered as true pathogens. The treatment of these NTM CRBSI involves catheter removal combined with antibiotic therapy3. These species are usually susceptible to multiple antimicrobial agents including aminoglycosides, cefoxitin, clarithromycin, minocycline, doxycycline, quinolones, trimethoprim/sulfamethoxazole, and imipenem11. Currently, there is no guidance or consensus on the appropriate antimicrobial therapy (whether single agent or combination therapy) for these infections or the duration of treatment for infections caused by NTM8.
Further information is needed to better understand the epidemiology including predisposing host factors, antibiotic susceptibility patterns, and appropriate duration of therapy for these infections particularly bloodstream infections caused by M. mucogenicum and M. neoaurum.