Nontuberculous Mycobacterium (Ditki Notes)

• Nontuberculous Mycobacteria are acid-fast, lipid-rich cell walls.
• These are free-living in soil and water.
• Biofilms allow them to persist in the environment.
• Some species use biofilms to cling to water pipes.
• When they break free from the biofilm, they can contaminate drinking and bath water.
• Microbes are ingested or inhaled and can gain access to the host via puncture wounds.

Runyon Classification

• Rapidly growing species grow within 7 days typically have low virulence.
• Slow-growing species Pigmented produce yellow carotenoids lending their colonies a yellow or golden color.
• Photochromogenic species, such as Mycobacterium kansaii, require exposure to light for pigment production.
• Scotochromogenic species do not require light exposure for pigment production.
• Non-pigmented slow growers include members of the Mycobacterium Avium Complex.

Slow Growing Nontuberculous Mycobacteria

• Mycobacterium kansaii is found in tap water.
• It causes pulmonary disease resembling tuberculosis, including lung cavitation with chest pain, cough with blood in the sputum (hemoptysis), and, in some patients, fever.
• Treatment varies, but can include rifampicin and ethambutol for at least 12 months.
• Mycobacterium Avium Complex (MAC) comprises 2 key species and 4 subspecies (in addition to several uncommon pathogenic species).
• Mycobacterium avium subspecies hominissuis
• Mycobacterium intracellulare

Lymphadenitis

• This is associated with Mycobacterium avium in the cervicofacial lymph nodes of young children

Disseminated Infection

• This is associated with Mycobacterium avium, HIV infection, and other immunocompromised conditions.
• It is characterized by high bacillary load, widespread organ damage, nonspecific symptoms, fever, night sweats, diarrhea, and weight loss.

Pulmonary Disease

• Mycobacterium avium complex risk is higher in immunocompetent individuals.
• Symptoms include cough, weakness, fatigue, and chest pain.
  • WITH underlying pulmonary disease presents as upper lobe infiltrates and cavitation, severe destruction can lead to respiratory failure.
    • Men who smoke, heavy alcohol drinkers, and adolescents with cystic fibrosis are particularly susceptible to this form of pulmonary disease.
  • WITHOUT underlying pulmonary disease presents as nodules and bronchiectasis.
    • Bronchiectasis is characterized by chronically dilated and scarred bronchial tubes, which allows infiltrates to accumulate.
    • The bronchial tubes of the right middle lobe and left lingula are most often affected, possibly because of their relative narrowness and length.
    • It tends to affect nonsmoking women over the age of 50.
    • Associated with thinness, mitral valve prolapse, and skeletal abnormalities, such as concave chest cavity (pectus excavatum).
    • One hypothesis suggests that this form of pulmonary disease results from chronic voluntary cough suppression, called Lady Windmere's syndrome

Rapid-Growing Nontuberculous Mycobacteria (RGM)

• Mycobacterium Abscessus, Mycobacterium fortuitum, and Mycobacterium chelonae RGM species tend to cause post-surgery infections in immunosuppressed patients.
• Mycobacterium Abscessus comprises 3 subspecies that respond differently to medications; thus, subspecies determination may be necessary for successful treatment.
• Mycobacterium Abscessus is resistant to many antibiotics and disinfectants.

Pulmonary disease

• Most cases are attributed to Mycobacterium Abscessus.
• Patients with underlying pulmonary disease, particularly cystic fibrosis, tuberculosis, and bronchiectasis, are most susceptible to infection.

Soft tissue and skin infections

• Post-surgical skin and soft tissue infections are associated with contaminated surgical equipment or solutions.
• Lesions tend to be red, painful, and can form nodules or ulcers.

Disseminated infection and lymphadenopathy

• This less common occurs in immunocompromised patients.

Meningitis and other CNS infections

• Possible, but rare.