Mycobacterium simiae

Mycobacterium simiae is a species of bacteria belonging to the genus Mycobacterium. It is a non-tuberculous mycobacterium (NTM) and is often found in the environment, particularly in water sources.

Taxonomy

Mycobacterium simiae was first described in 1965 by Kubica et al. It is part of the Mycobacterium avium complex (MAC), a group of species that are genetically related and have similar growth characteristics. Other members of the MAC include Mycobacterium avium and Mycobacterium intracellulare.

Characteristics

Mycobacterium simiae is an acid-fast, non-motile, rod-shaped bacterium. It is slow-growing, with colonies typically appearing after three to four weeks of incubation. The colonies are smooth and non-pigmented.

Pathogenicity

Mycobacterium simiae is an opportunistic pathogen, meaning it can cause disease in individuals with weakened immune systems, such as those with HIV/AIDS or those undergoing immunosuppressive therapy. Infections caused by M. simiae are typically pulmonary, but can also involve the lymph nodes, skin, and other organs.

Diagnosis and Treatment

Diagnosis of M. simiae infection is based on culture of the organism from clinical specimens, such as sputum or tissue biopsies. Treatment typically involves a combination of antibiotics, including macrolides, rifamycins, and aminoglycosides. However, M. simiae is often resistant to many standard anti-tuberculosis drugs, making treatment challenging.

Epidemiology

Mycobacterium simiae is found worldwide, but is most commonly reported in the southern United States, the Caribbean, and the Middle East. It is thought to be transmitted from the environment, rather than from person to person.

See Also

• Non-tuberculous mycobacteria
• Mycobacterium avium complex
• Opportunistic infection