tuberculosis Flashcards
1
Q
how many people have latent TB?
A
1/4
2
Q
describe the pathogenesis of tuberculosis? 6
A
- 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
3
Q
describe the pathology of TB? 6
A
- 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
4
Q
describe granulomatous inflammation? 6
A
- rim of lymphocytes
- fibroblasts
- central infected macrophages
- central necrosis-> caseation
- secretion of cytokines-> activate macrophages to kill bacteria
- acid fact bacilli
5
Q
describe the transmission risk of TB? 5
A
- 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
6
Q
describe the disease progression of TB? 3
A
- primary TB
- bacilli can overcome immune system soon after initial infection (1-5%)
- latent TB
- can have reactivation of disease
- this increases with immunosuppression
7
Q
how do we diagnose TB? 4
A
- active:
- identify infected area
- isolate the organisms
- obtain information regarding susceptibility to antibacterial
- latent
- identify immune response to TB proteins or TB specific antigens
8
Q
describe the Mantoux test? 3
A
- 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
9
Q
what are interferon gamma release assays? 3
A
- 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
10
Q
describe pulmonary TB? 3
what are the clinical features? 6
diagnosis? 3
A
- 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)
11
Q
describe extra-pulmonary disease? 2
sites? 6
A
- more common in non-UK born, asian origin
- reactivation
- lymph nodes
- CNS
- bones (Potts disease of the spine)
- genitourinary system
- GI tract
- disseminated/miliary
12
Q
what is TB lymphadenitis? 3
A
- often gets worse on treatment (paradoxical reaction)
- can form sinus tracts with chronic discharge
- cold abscess formation
13
Q
what is disseminated/ miliary TB? 6
A
- fevers, sweats, weight loss, malaise
- respiratory symptoms
- GI or CNS symptoms
- abdominal pain/ diarrhoea
- headache or confusion and altered mental state
- hepatomegaly
14
Q
name some other forms of TB? 6
A
- 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
15
Q
how do we control TB? 6
A
- 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
