Mycobacteria

• Slender, rod-shaped (0.2- 0.6 um x 1- 10um in size) 
• Nonmotile; non-spore formers 
• Strictly aerobic 
• Increased CO2 – enhances growth

RAPID GROWERS 

• Grows in simple media 
• Grows 2-3 days 
• 20-40°C

DISEASE-ASSOCIATED MYCOBACTERIA 

• Requires 2-6 weeks 
• Requires complex media 
• Has specific optimal temp.

MTB COMPLEX 

• M. microti – TB in immunocompetent and compromised 
• M. africanum – TB in tropical africa 
• M. tuberculosis 
• M. bovis – TB in cattle and other ruminants 
• M. canettii

1 – 5 um – size of droplet that can transmit MTB

Decreased antigen; Increased Hypersensitivity rxn. – granuloma formation

Increased antigen and hypersensitivity rxn – tissue necrosis

MOST COMMON SITES OF SPREAD OF MTB (in-order) 

• Spleen 
• Liver 
• Lungs 
• Bone marrow 
• Kidney 
• Adrenal glands 
• Eyes

MOST COMMON EXTRAPULMONARY SITES IN HIV PATIENTS 

• Lymph nodes 
• Genitourinary tract 
• Abdominal cavity

Miliary TB 

• Most cases is in CHILDREN 
• Common form of TB in HIV-infected people

Pott Disease – skeletal TB of the spine

Gibbus – hump of the deformed spine in Pott’s Disease

MDR-TB – resistant to atleast Isoniazid & rifampin (1° treatment)

XDR-TB – resistant to 1° treatment, fluoroquinolone, atleast 1 of 3 injectable 2nd-line anti-TB drugs

Mycobacterial Test 

• Direct Sputum Smear Microscopy (DSSM) – primary diagnostic method 
• Chest X-ray – used to complement bacteriologic testing 
• TB culture & DST (Ogawa & LJ) – routine diagnostic test for DR – TB 
• Tuberculin Skin test / Mantoux Test / PPD Test – basic screening tool for TB infection 
• Xpert MTB / RIF & Line Probe Assay – rapid test that detects MTB and rifampicin resistance