TB (MED 1 ILOs)

Question 1

LOs

Answer 1

explain the difference between pulmonary and extra-pulmonary TB

explain the principal apporaches to managing TB

describe the clinical tests used to identify a TB infection

understand how HIV can influence the progression of TB and vice versa

understanf the interaction and potnetial adverse effects of drugs used in the treatment of HIV/tuberculosis co-infection

Question 2

Mycobacterium tuberculosis

Answer 2

• aerobic- have a predilection for lung apices
• high lipid content in cell wall

likely the reason for virulence and resistance

“acid fast bacillus” staining not decolourised by alcohol

unable to gram stain

use ZN staining instead

• Slow growing (resistant to being killed) and long living
• group of genetically related mycobacteria (mycobacterium TB ciomplex)

Question 3

TB infection and spread

Answer 3

airborne droplet nuclei- coughing singing

can remain suspended in air for hours

overcrowded living, prisons

oropharyngeal/ intestinal deposition

Question 4

what can happen to a granuloma over time

Answer 4

calcify then

a) resolution of infection
b) latent TB to active

Question 5

Symptoms of TB

Answer 5

• pulmonary-cough, wheeze, haemoptysis, breathlessness
• extrapulmonary- CNS, bones, GI etc.
• Constitutional- fever, cachexia, night sweats

Question 6

primary tB

Answer 6

Symptoms of tb but may be asymptomatic or mild

look for people who have had close contact over 2-5 years

usually only a clinical disease in children/ immunosuppressed

Question 7

radiological signs of primary TB

Answer 7

Mediastinal lymphadenopathy

Pleural effusion

Lobal collapse/ consolidation

Miliary shadowing

Classically, pneumonia with enlarged hilar (root of lung) lymph nodes

Question 8

CXR appearance of post primary TB

Answer 8

• look at apices
• soft, “fluffy” or nodular in upper zones
• cavitation
• consolidation
• lymphadenopathy

Question 9

miliary TB

Answer 9

haematogenous spread

often suggets immunodeficiency

in the lung: widespread fine nodules of uniform distribution

patients are very unwell

Question 10

extrapulmonary TB

Answer 10

most commonly affects lymph glands, pleura, bone and joints, GU and CNS

Question 11

TB lymphadenitis

Answer 11

Used to be called scrofula

Commonest presentation

Cervical nodes most affected

Slowly progressing swelling

Fever

Diagnosis fine needle aspiration

Treatment  standard treatment for TB

Question 12

CNS TB

Answer 12

TB meningitis

Meningeal symptoms

Cranial nerve palsies

Diagnosis through CNS examination

Question 13

diagnosis of TB

Answer 13

microbiology- sputum sample, ZN staining to show acid fast bacilli, 10-100 microorganisms needed to be diagnostic

bronchoscopy

othrt tissue samples if extrapulmonary (morning urine for renal)

molecular techniques- PCR, whole genome sequencing

Question 14

PCR for diagnosis of TB

Answer 14

rapid confirmation of mTB complex

can identify rifampcin resistance

Question 15

whole genome sequencing for TB diagnosis

Answer 15

1. Identifies species, drug resistance and can identify transmission cluster
2. Important in controlling endemics
3. Increasingly quick and affordable

Question 16

rifampcin

Answer 16

Bactericidal

Kills both active and semi-dormant bacteria

Potent inducer cytochrome P450

High drug interactions

Anti-retrovirals

Side effects: orange urine, tears, stain contact lenses

Rash, skin reactions itch

Abnormal liver function  usually transient

Influenza like reaction

Haemolysis rare

Thrombocytopaenia

Renal failure

Shock

Question 17

isoniazid

Answer 17

Only active against MTB

Kills actively dividing cells

Metabolised by acetylation

Hepatoxicity (small AST increase) this increases with age

Histamine food reactions

Nausea and vomiting

Aplastic anaemia

Cutaneous hypersensitivity

Neurotoxicity

Question 18

ethambutol

Answer 18

bacteriostatic

Inhibits arabinosyl transferase

Question 20

principles of treatment

Answer 20

start with all 4 drugs and do not reduce until you’ve had 2 months of treatment

consider changing to more sensitive drugs after 4 months

Question 21

side effects of treatment: advice to patients

Answer 21

Nausea/ abdominal pain

Persistent vomiting/ jaundice-stop drugs and seek attention  heaptic damage

Red urine and contact lenses

Visual disturbances

Drug interactions

Isoniazid induced peripheral neuropathy

Question 22

IRIS- immune reconstitution inflammatory syndrome

Answer 22

Paradoxical worsening of symptoms

Absence of alternative diagnosis

Usually starts 2 weeks after starting antiretrovirals, but can be up to 2 months

Associated with more advanced HIV, lower CD4 count

Significant morbidity requiring hospital admission

Treat with prednisolone

Question 23

how important is contact tracing in TB

Answer 23

vital

Question 24

aidentificatio of latent tB

Answer 24

identify with skin test or IGRA

Question 25

risk of developing TB is increased by:

Answer 25

Recent contact (<2 years) with infectious (smear positive) individual

HIV coinfection/ immunosuppressed

Chronic alcohol excess

Diabetes

Anti-TNF drug therapy/ immunosuppressive therapy

Partial gastrectomy

Question 26

how to support the patient to be compliant with TB treatment

Answer 26

Monitoring the patient at home

Ensuring patient is taking medication as prescribed

Maintaining adequate medication

Monitoring side effects of Abx

Supporting patient attendance with hospital appointments