Mycobacteriaceae

Mycobacteriaceae is a family of bacteria within the order Mycobacteriales of the phylum Actinobacteria. Members are characterized by a thick, waxy cell envelope rich in mycolic acids, which gives them acid-fast staining properties and a Gram stain that is often inconclusive. The family is dominated by the genus Mycobacterium, which includes many environmental species as well as several important pathogens. Other members are less well known but share the distinctive cell wall and slow growth.

Most species are aerobic and nonmotile rods. They typically require enriched, specialized media and long incubation times for growth, with generation times ranging from rapid growers to days or weeks for slow growers. Colonies often appear dry, waxy, and pigmented.

Ecology and disease: Mycobacteriaceae species inhabit soil, water, and biofilms and can persist in the environment. Pathogenic members cause human disease, most notably the Mycobacterium tuberculosis complex, which causes tuberculosis, and Mycobacterium leprae, the agent of leprosy. Non-tuberculous mycobacteria (NTMs) such as M. avium complex and M. kansasii cause pulmonary and extrapulmonary infections, particularly in people with underlying lung disease or immune compromise.

Diagnosis and treatment: Detection commonly relies on acid-fast staining, culture on specialized media such as Löwenstein–Jensen or Middlebrook formulations, and molecular methods. Treatment requires prolonged multidrug regimens tailored to the species and susceptibility profile and is often complicated by intrinsic drug resistance.

Genomics and vaccines: The genomes are relatively large and G+C rich. The cell wall lipids contribute to intrinsic resistance and virulence. BCG, a vaccine derived from M. bovis, provides limited protection against pulmonary tuberculosis.