TB Flashcards
Is TB caused by virus or bacteria if so what is the most common causative organism
Bacteria -
Myobacterium TB
List causative organisms
• mycobacterium TB
• M. Bovis (anima to human or via unpasturised milk)
• m.african (mainly in west Africa)
Can latent or inactive TB spread from one person to another
No
Describe the pathogenesis
- Infected aerosol droplets which contain myobacterium TB enters the air via infected person (can remain in air for hours)
- Once inhaled it enters the alveoli where macrophages engulf it.
- Macrophages recruit T cells and other inflam cells forming a granuloma around the bacteria.
This is latent TB, asymptomatic and does not spread
- however in immunosuppressed individuals the bacteria can reactivate into active TB, where it escapes granuloma and replicate.
In active TB, bacteria can enter blood stream via lymphatic system to other organs - dismounted TB (millary TB), affecting kidneys, brain, bones and liver
- Cavitary lesions occur - from tissue destruction in the alveoli. This can increase risk of transmission (visible on chest x ray)
TB risk factors
remember risk factors do not need to be present
• < 5 years
• born in a area with high prevalence
• take immunosuppressive agents - corticosteroids
• co-morbidities (CKD) or Kidney transplant, diabeties
• hx of TB
Clinical presentations of active TB
• low grade fever
• night sweats
• sputum production
• weight loss
• anorexia
• heamoptysis
Locations of extra pulmonary TB
• lymph nodes (most common)
• CNS
• joints/bones
• abdominal area
• plurea
What is Millary TB?
When bacteria entered blood stream and affects organs
Symptoms of pulmonary TB
• breathlessness
• heamoptysis
• persistent productive cough
Symptoms of joint and bone pain indicates what type of TB (extrapulmonary)
Skeletal TB
Symptoms of abdominal pain?
GI TB
Urinary symptoms
Genitoururinary TB
Sterile pyuria (WBC in urine)
Renal TB
Symptoms of headache, vomiting, confusuion and cranial nerve pain
Meningitis TB
Symptoms of breathlessness, chest pain and ankle swelling?
Pericarditis TB
Ocular symptoms?
Ocular TB
Tests/investigations for Latent TB?
+
Pulmonary
+
Extra pulmonary
• Mantoux test (skin test)
• IGRA
• AFB - for sputum
• Chest x ray
• sputum microbiology
• cheat x ray
• CT
• ultrasound
• respiratory sample
Differential Diagnosis of TB
• COPD
• ASHMA
• lung cancer
• COVID
• fever
• cough
Who should the doctor inform about active TB?
Local public health - to help track and trace
Should the doctor inform public health about latent TB
No
What is the TB vaccine
BCG - contains a live strain of mycobacterium Bovis
Who should the BCG vaccine be offered to?
• infants at high exposure
• children living with those with respiratory disorders
• <35 at occupational risk
What treatment is used in the initial phase of active TB?
rivampicine + isoniazide (with pyridoxine) + Ethanbutol + pyrazinamide
For 2 months
What treatment is used in continuous phase
rivampicine + isoniazide (with pyridoxine)
For another 4 months (6 month of treatment in total)
What drugs are used for treatment in Latent TB (2 options
rifampicin + isoniazide (with pyridoxine) - 3m
isoniazide (with pyridoxine) - 6 m
Which agent is a pro drug
Pyrazinamide
Rifampicin moa?
Inhibits RNA synthesis and binds to b subunit
Isonizide MOA
inhibits synthesis of mycolic acid
Ethambutol MOA
Disrupts mycobacterium cell wall
Pyrazinamide MOA
Accumulates the acidic environments of the the bacteria and affects its energy
Which drug affects the eyes and thus eye test is required?
Ethambutol (by snellen chart)
Which drug turn urine red
Rifampicin
Which drug increases uric acid?
Ethambutol
Which drug should be avoided in patients with gout
Pyrazinamide
Why is isoiazide taken with Pyridoxine
Isoniazide can cause neuropathy so it is taken with this B6 vitamin
What is DOT and who is it offered to
Directly observed therapy
Offered to:
• hx or current poor adherence
• hx of homelessness
• hx drug miss-use
• previous treatment to TB
• those in denial of TB
• cognitive disorder
• those who ask
• have been to prison within last 5 years
Is TB curable?
Yes
Why is TB common in those with HIV
In HIV CD4 cells decrease (weakening of immune system)
CD4 cells are key in TB, they activate macrophages to kill bacteria and form granulomas
Is M. TB Aerobic or anaerobic
Aerobic (needs oxygen)
Remember lungs are oxygen rich
Is cavitation more prominent in latent or active tb
Active tb
Does TB bacci stain red/pink or blue
Red/pink
When reactivation occurs after latent TB, where in the lungs does it multiple
Upper lungs - oxygen levels are high promoting bacterial growth
Can cavity lesions increase risk of transmission
Yes
