Mycobacterium TB

Question 1

General manifestations of TB

Answer 1

Fever, fatigue, night sweating and weight loss.

Question 2

manifestations of Pulmonary TB

Answer 2

chronic cough for months + hemoptysis

Fever, fatigue, night sweat, increased weight loss

Question 3

manifestations of Extrapulmonary TB

Answer 3

1. Scrofula

● Scrofula is cervical lymphadenitis (usually located unilaterally)

● It’s the most common extra-pulmonary TB manifestation.

2. Erythema nodosum

● Tender nodules in the extensor surface of tibia and ulna

● Usually in patients with potent cell mediated immunity

3. GIT TB

abdominal pain, diarrhea, hemorrhage, intestinal obstruction.

● Most common site of involvement: ileocecal valve

● GIT tuberculosis can be caused by either:

• Mycobacterium Tuberculosis: if the patient swallows his sputum.
• Mycobacterium Bovis: by drinking of unpasteurised milk

4. Oropharyngeal TB
   Painless ulcer
5. Renal TB

● Dysuria, hematuria, flank pain in addition to the general features of Tb.

● Sterile pyuria

Question 4

The two most common clinical manifestations of Mailliary TB

Answer 4

● Tuberculous Meningitis:

● Causes Subacute (chronic) meningitis
● CSF contains high lymphocytes count

● Tuberculous Osteomyelitis:
● Pott’s disease (vertebral osteomyelitis)

Question 5

90% of TB infections are asymptomatic because of good cell mediated immunity (CMI).

but Reactivation of TB in ICP These include:

Answer 5

• AIDS patients
• Measles infection: reactivation of TB due to binding CD46 and production of IL-12
• Rheumatoid Arthritis: because they are given Infliximab (an immunosuppressor)
• Organ Transplantation

Question 6

➢Transmission of Mycobacterium TB and Bovis

Answer 6

By air dropping

By drinking unpasteurised milk

Question 7

To differentiate between Brucellosis and TBتساؤلات

Answer 7

● In the case of pulmonary TB in addition to (Fever + fatigue + night sweat + increased weight loss) you have pulmonary symptoms.

● In Brucellosis: you have in addition to the above complications:

• Arthritis or osteomyelitis
• Back ache or limb ache
• Complications of orchitis

Question 8

➢Pathogenesis of Mycobacterium TB

Answer 8

● By intracellular infection (of macrophages and cells of the reticuloendothelial system “RES”).

LERP = Exported repetitive Protein which inhibits phagosome-lysosome fusion.

Question 9

TB causes 2 types of lesions

Answer 9

● Exudative lesion

● Granuloma formation: which is a type 4 hypersensitivity reaction caused by the immune system.

• Good immunity: Increased symptoms of TB.
• Bad immunity: Decreased symptoms of TB.

Question 10

Primary infection of TB Targets

Reactivation of TB Targets

Answer 10

● lower lobe of the 🫁

● Apex of the lung
● Sites of high oxygen delievery: Kidney, Brain, Bone

Question 11

What is a tubercle? How it can cause dissemination of infection لدي تساؤلولات

Answer 11

It’s a granuloma surrounded by fibrous tissue (tubercle or Ghon focus).

● By erosion of the bronchus and disseminating to other sites of the lung.
● By bloodstream reaching distant organs and causing Miliary TB.

Question 12

What is Ghon-complex ? تساؤلات

Answer 12

Tubercle + the lymph node which drains it .

Question 13

➢Diagnosis of TB

Answer 13

1. Clinical diagnosis (History & examination)
2. Specimen collection:

● Pulmonary TB: sputum.

● GIT TB: stool.

● Milliary TB: blood.

● Tuberculous Meningitis: CSF.

3. Microscopy
   add NaOH

Stain Kinyoun acid fast stain or Ziehl-Neelsen acid fast stain).

● We see red bacilli with blue background .

4. Culture:

● Lowenstein Jensen (LJ) medium:
- Consists of Egg yolk (nutrition) + Malachite green بقتل البقية 😸
- This takes 6-8 weeks (not practical)

● Radioactive BACTEC medium (most favorable)
- Depend on radioactivity of CO2 ,
- This takes 3-4 weeks (faster than the LJ medium)

5. Biochemical tests:

● Produces Niacin: The only Mcobacterium that produces Niacin is Mycobacterium Tuberculosis.

● Catalase (+ve.)

6. PCR