Atypical Mycobacteria

Question 1

Atypical mycobacteria

Answer 1

Atypical mycobacteria AKA ‘mycobacterium other than M.tuberculosis” or “MOTTS)

Named atypical -> as they differ from M.tuberculosis in various ways.

!!! Most important difference: atypicals are found in the environment (saprophytes), whereas M.tuberculosis is found only in humans.

Divided into subgroups:
- slows growers
- rapid growers
> based on whether they form colonies in more than or less than 7 days

Question 2

Group I

Answer 2

Photochromogens

Growth rate: Slow

Typical species:

M.kanasasii
- cause tuberculosis-like disease

M.marinum

• “swimming pool granuloma” or “fish tank granuloma”
• a skin lesion at the site of an abrasion acquired in a swimming 🏊‍♀️ pool or an aquarium 🐟

Question 3

Group II

Answer 3

Scotochromogens

Slow

typical species:

M.scrofulaceum
- causes scrofula, which manifests as swollen, non-render cervical lymph nodes (cervical adenitis)

Question 4

Group III

Answer 4

Nonphotochromogens

Slow

Typical species:

M.avium-intracellulare complex (MAC)

• especially in immunocompromised patients (i.e. AIDs)
• highly antibiotic resistant

M.ulcerans

• 3rd most common mycobacteria infections in humans
• causes Buruli Ulcer
• treatment is surgical excision requiring long hospitalization

Question 5

Group IV

Answer 5

Rapid growers

Rapid

Typical species:

M.fortuitum complex

• superficial and systemic diseases.
• causes infections of prosthetic joints and indwelling catheters.
• causes skin and soft tissue infections at the site of puncture wounds
• the organisms are usually resistant to most antituberculosis drugs