tuberculosis

Question 1

how many people have latent TB?

Answer 1

1/4

Question 2

describe the pathogenesis of tuberculosis? 6

Answer 2

• airborne droplet spread
• inhaled- deposited in terminal airspaces
• macrophages ingest bacilli- replicate within the endosomes
• transported to regional lymph node where they are killed or multiply (primary TB)
• dormant- asymptomatic
• proliferate after a period of latency-> reactivation disease

Question 3

describe the pathology of TB? 6

Answer 3

• aerobic bacillus
• divides every 16-20 hours (slow)
• cell wall but lacks phospholipid outer layer membrane
• does not stain strongly with Gram stain (weakly positive)
• retains stains after treatment with acids (acid fast bacillus)
• causes granulomatous inflammation

Question 4

describe granulomatous inflammation? 6

Answer 4

• rim of lymphocytes
• fibroblasts
• central infected macrophages
• central necrosis-> caseation
• secretion of cytokines-> activate macrophages to kill bacteria
• acid fact bacilli

Question 5

describe the transmission risk of TB? 5

Answer 5

• close contacts with infectious cases
• contact with high risk groups (high incidence country, frequent travel to high incidence areas)
• immune deficiency (HIV, steroids, chemotherapy)
• lifestyle factors (drug/ alcohol misuse, homelessness, prison inmates)
• genetic susceptibility

Question 6

describe the disease progression of TB? 3

Answer 6

• primary TB
• bacilli can overcome immune system soon after initial infection (1-5%)
• latent TB
• can have reactivation of disease
• this increases with immunosuppression

Question 7

how do we diagnose TB? 4

Answer 7

• active:
• identify infected area
• isolate the organisms
• obtain information regarding susceptibility to antibacterial
• latent
• identify immune response to TB proteins or TB specific antigens

Question 8

describe the Mantoux test? 3

Answer 8

• requires circulating memory T lymphocytes and the ability to mount a delayed hypersensitivity reaction
• cross reactive with other mycobacterial antigens so non-specific
• may be falsely negative in severely ill or immunosuppressed individuals

Question 9

what are interferon gamma release assays? 3

Answer 9

• ELISPOT/ELISA= enzyme linked immunological assay fo release of interferon gamma in whole blood following stimulation by specific TB antigen
• more specific than Mantoux
• does not differentiate between latent infection and disease

Question 10

describe pulmonary TB? 3

what are the clinical features? 6

diagnosis? 3

Answer 10

• majority of cases
• infection risk
• cavitary disease- more infectious
• cough
• haemoptysis
• chest pain
• weight loss
• fever
• night sweats
• chest imaging
  -sputum
  (when
  you see upper lobe consolidation in CT, it could be TB)

Question 11

describe extra-pulmonary disease? 2

sites? 6

Answer 11

• more common in non-UK born, asian origin
• reactivation
• lymph nodes
• CNS
• bones (Potts disease of the spine)
• genitourinary system
• GI tract
• disseminated/miliary

Question 12

what is TB lymphadenitis? 3

Answer 12

• often gets worse on treatment (paradoxical reaction)
• can form sinus tracts with chronic discharge
• cold abscess formation

Question 13

what is disseminated/ miliary TB? 6

Answer 13

• fevers, sweats, weight loss, malaise
• respiratory symptoms
• GI or CNS symptoms
• abdominal pain/ diarrhoea
• headache or confusion and altered mental state
• hepatomegaly

Question 14

name some other forms of TB? 6

Answer 14

• Skeletal TB
• Genitourinary TB- kidney/ bladder/pelvic involvement, Pus in urine but repeatedly negative standard cultures
• TB enteritis- weight loss, diarrhoea, blood in stools
• TB of the eye- any part of the eye
• Pericardial TB
• CNS TB- TB meningitis, TB arachnoiditis, tuberculoma, spinal cord compression

Question 15

how do we control TB? 6

Answer 15

• government global policy
• consider the diagnosis
• early diagnosis and treatment (even if negative cultures or smear)
  -optimal treatment and adherence
  -contact tracing
  prevention- BCG vaccine
  -latent treatment programs- prevent TB becoming active

Question 16

what are the first line drugs for TB? 6

Answer 16

• standard is a minimum of 6 months
• standard quadruple therapy for 2 months- Isoniazid, Rifampicin, Pyrazinamide, Ethambutol
• 4 months of Isoniazid and Rifampicin- standard dual therapy
• taken all together on an empty stomach 1 hour before breakfast, compliance is essential for cure
• if CNS involvement, the continuation phase of treatment is extended to 10 months making a 12 month treatment plan
• latent treatment- 3 months rifampicin/ isoniazid

Question 17

what are the main treatment side effects for TB? 5

Answer 17

• Pyrazinamide= hepatoxicity, joint pain
• Rifampicin= hepatoxicity, reddish colour to the urine
• Isoniazid= hepatoxicity, fever, peripheral neuropathy and optic neuritis
• Ethambutol= peripheral neuropathy, optic neuropathy and gout
• All= nausea and skin rashes