Microbiology: Tuberculosis and other mycobacteria

Question 1

Cough with haemoptysis, fever, with night sweats, weight loss, malaise. Most likely diagnosis?

Answer 1

Mycobacterium tuberculosis

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Question 2

Describe mycobacterium

Answer 2

gram +ve, aerobic, acid alcohol fast, thick waxy cell wall.

Question 3

What are the two ways in which TB can present?

Answer 3

• Post-primary (Young adults)
• Reactivation
• Primary (Children, elderly, HIV)

Question 4

Outline presentation of Post-primary TB

Answer 4

• Upper lobes affected
• May progress rapidly to cavitation
• Classic lesion: Caseating granuloma

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• Miliary spread is rare
• Healing by fibrosis + Calcification

Question 5

Outline presentation of Primary TB

Answer 5

• Usually occurs in Children, elderly or HIV patients
• Can be asymptomatic
• Generalised lymphohaematogenous spread
• Mulitplies at pleural surface (Ghon Focus)
• Taken by Mo to LN (Primary complex).

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• Granuloma is characteristic lesion (Langhan’s giant cells)
• Tuberculoma
• Miliary TB

Question 6

Cough with fevers and night sweats. Caseating granuloma. Most likely diagnosis?

Answer 6

Post-primary TB

Question 7

Cough, fevers, weight loss in elderly man. Diffuse miliary infiltrate on chest xray. Most likely diagnosis?

Answer 7

Primary TB

Question 8

Outline management for TB

Answer 8

• 1st line
• Rifampicin (6 months)
• Isoniazid (6 months)
• Pyrazinamide (2 months)
• Ethambutol (2 months)
• 2nd Line
• Injectables (Eg capreomycin)
• Quinolones (Eg Moxifloxacin)

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“RIPE”

Question 9

Outline management for TB meningitis

Answer 9

• 1st line
• Rifampicin (8-10 months)
• Isoniazid (8-10 months)
• Pyrazinamide (2 months)
• Ethambutol (2 months)
• 2nd Line
• Injectables (Eg capreomycin)
• Quinolones (Eg Moxifloxacin)

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“RIPE”

Question 10

So you’ve got a patient with TB currently recieving appropriate treatment. They have raised transaminases. What is the most likely cause of this?

Answer 10

Rifampicin

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It also induces cyt P450

+causes orange secretions

Question 11

A 45 year old man with TB is currently recieving appropriate treatment. He complains that his urine has turned a reddish orange colour.

What is the most likely cause of this?

Answer 11

Rifampicin

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It also induces cyt P450

+causes raised transaminases

Question 12

A 45 year old man is seen for follow up in a TB clinic and is recieving the appropraite treatment. He complains of loss of sensation in his toes.

What is the most likely cause of this?

Answer 12

Isoniazid causing peripheral neuropathy

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Give B6/Pyrodoxine

Question 13

A 45 year old man is seen for follow up in a TB clinic and is recieving the appropraite treatment. A recent blood test shows raised serum uric acid.

What is the most likely cause of this?

Answer 13

Hyperuricaemia due to Pyrazinamide

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Also causes hepatotoxicity

Question 14

A 45 year old man is seen for follow up in a TB clinic and is recieving the appropraite treatment. He complains of visual disturbances.

What is the most likely cause of this?

Answer 14

Optic neuritis caused by ethambutol

Question 15

Sputum microscopy:

Ziehl–Neelsen stain: show acid fast bacilli.

gram +ve rods.

Most likely diagnosis?

Answer 15

Mycobacterium tuberculosis

Question 16

Outline the investigations for TB

Answer 16

• CXR
• Sputum cultures (x3) with ZN staining
• Tuberculin skin tests (TSTs), aka mantoux test
• IGRA (Interferon gamma release assays)

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ZN stain = Ziehl–Neelsen stain

Question 17

Extrapulmonary TB: Common sites?

Answer 17

• Lymphadenitis
• Pericarditis
• Peritonitis (Abdominal)

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+ Others. I guess any extra symptom could be extrapulmonary TB

Question 18

Fever, night sweats, weight loss, back pain.

CT reveals Iliopsoas abscess.

Most likely diagnosis?

Answer 18

Spinal TB

Question 19

Head aches, neck stiffness, fevers, previous night sweats. Impaired consciousness. Most likely diagnosis?

Answer 19

TB Meningitis

Question 20

Depigmented skin, macules, plaques, nodules, trophic ulcers. Sensory neuropathy. examination of eyes show kerititis. Skin biopsy shows acid fast bacilli. Most likley diagnosis?

Answer 20

Leprosy, Hansen’s disease

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M. Leprae + M. Lepromatosis

Question 21

BCG vaccine is contraindicated in which condition?

Answer 21

HIV

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Can lead to IRIS (Immune reconstitution inflammatory syndrome).

Question 22

45 south Asian man, new diagnosis of HIV, starts recieving HIV treatment. Develops fevers and night sweats. Most likely diagnosis?

Answer 22

Immune reconstituion inflammatory syndrome (IRIS) due to underlying TB

Question 23

A 35 year old man from South Asia has a cough, high fever or chills, night sweats, abdominal pain, diarrhoea. History of HIV. Pharyngitis is also noted. Bronchoscopic lung biopsy showed a poorly defined granuloma consisting of pale blue, striated histiocytes filled with mycobacteria

Most likely diagnosis?

Answer 23

Mycobacterium Avium complex

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striated histiocytes

Question 24

A 35 year old man who presents to his GP with Clusters of plaque/papules. He has a history of Crohn’s disease for which he takes azathioprine. He owns a swimming pool. Most likely diagnosis?

Answer 24

M. Marinarum (Fish tank granuloma)

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Associated with impaired immunity

Question 26

A 35 year old man has recently come bacl from travelling around Austrailia. he developed a painless nodule and has presented to the GP after it has causes ulceration and scarring. Skin biopsy reveals acid fast bacilli. Most likely diagnosis?

Answer 26

M. Ulcerans (Buruli Ulcer)

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