Mycobacteria

Question 1

Ziehl-Neelsen aka: used fro:

Answer 1

The “acid fast” stain • Contains carbolfuchsin • Used to detect mycobacterium (especially TB) • Also used for Nocardia

Question 2

Mycobacterium avium complex MAC

found in:

causes_mostly in:

biggest tip off: (2 things)

treatment/prophalyxis:

Answer 2

Found in water and soil

Inhaled or ingested

Very rare cause of pulmonary disease in non-HIV

HIV/AIDS: Disseminated disease

Very low CD4 count (<50)is the biggest tipoff • Fever, sweats, abdominal pain, diarrhea, weight loss • Severe anemia • Hepatosplenomegaly • ↑ alk phos, ↑ LDH • Often no lung findings (if lung findings → it’s TB)

Diagnosis: Blood culture (takes 7 days or more) Treatment: • Clarithromycin plus Ethambutol • Prophylaxis: Azithromycin

Question 3

M. Kansasii

Answer 3

• Similar pathology but less virulent than TB • Fever, sweats, cough, dyspnea • CXR infiltrates

Question 4

M. Leprae Leprosy (Hansen’s Disease)

important micobio info:

grows best at:

reservoir:

causes:

Answer 4

Obligate intracellular organism

Grows very slowly - cannot be cultured

Grows best at cool temps (27 to 33°C) • Infection involves skin • Extremities, face

Reservoir is armadillos • Mode of transmission unclear

Causes granulomatous inflammation • Mostly found in developing countries • Most US cases occur in immigrants

Question 5

Tuberculoid leprosy

Answer 5

milder disease, • Patches of hypopigmented skin • Loss of sensation over affected area

Strong cell-mediated TH1 response contains infection • Lesions show granulomas, few bacteria

Question 6

Lepromatous Leprosy

Answer 6

Diffuse skin lesions

Often deformed, thickened skin • Hypopigmentation and hair loss

Severe neuropathy (weakness, regional anesthesia) • Th2 response • Humoral immunity whihc is inferior and causes more severe diseas

Depressed cell-mediated immunity • Antibodies cannot reach intracellular bacteria

Lesions: • Multiple bacteria • No granulomas

Question 7

M. Leprae Leprosy (Hansen’s Disease)

diagnosis & treatment :

Answer 7

Diagnosis: • Acid-fast organisms on skin biopsy • Note: False positive VDRL

Treatment: • Tuberculoid: dapsone and rifampin (6 months) • Lepromatous: dapsone, rifampin, and clofazimine (years)