Tuberculosis Flashcards
Definition
Chronic granulomatous disease caused by mycobacterium tuberculosis affecting lungs
Features of mycobacterium tuberculosis
slow growing
rods (bacillus)
high contents of lipids - Ziehl Neeson stain
Transmission of TB
Airbourne
Coughing and sneezing- respiratoyr droplets- droplets evaporate- suspended in air and circulated
Pattern of infection in TB
Primary TB
Secondayr TB
Miliary TB
Primary TB
- initial infection
- usually children
- May be entirely asymptomatic
- Bacilli are transported through lymphatics
- granulomatous hilar lymph node infection in lung,known as Ghon focus
- infection is then arrested
- Tuberclin tests become positive after this
- may cause mild cough, wheeze, erthema nodosum
Difference between ghon focus and ghon complex
Ghon focus- subplerual granuloma
Ghon complex- granuloma with associate lymph node
Secondary TB
Reactivation of disseminated dormant organisms
- particullarly in the immunocompromised
- florid and widespread
- upper lung lobes and cavitation
miliary TB
Widespread haematological spread of small milet seed sized granulomas
Failure of Primary/secondary can gain entry throughout the body and set up many foci
Symptoms of TB
Pulmonary tB (90%)
- cough, haemoptysis, shortness of breath
- constitutional symptoms (fever, night sweats, fatigue, loss of apetits, lymphadenopathy)
10% extrapulmonary features
- CNS (meningitis)
- Eyes (blurred vision)
- CVS (constritive perocarditis)
- Renal (dysuria, haematuria)
- GI (abdnominal pain, ascities)
- Skeletal(arthritis, osteomyelitis)
- skin (LUPUS)
Diagnosis of TB
Active TB:
Chest xray
Samples
- sputum (patients who are not expectorating can induce with hypotonic saline, 3 separate samples including one early morning , collected and examined for TB bacillus Ziehl neison stain)
- CT- differnetiates active TB
- Bronchoscopy - intra-airway neoplasm
- pleural effusion - tapped and examined for TB
latent TB
- Manteoux tuberculin skin test (used to screen peope at high risk for TB)
others
T-spot test
Lymph node biopsy
What does the Ziehl Neelsen stain test for
rapid direct mircoscopy for acid-alcohol-fast bacili (AAFBs)
How long does the culture take?
at least 6 weeks
therefore treatment started before culture results are back and continued even if cultures are negative
Mantoux test
Artificially injected material into skin
Harness immune response
Infiltration of lymphocytes
T-spot test
Blood take RBCs and nuclear cells removed Immunologically competent cells left Purified TB added T cells release interferon y Antibody for interferony captured at the bottom
Spread of infection
Renal
- aggresive destruction of parenchyma
- WBCs in urine, negative culture
CNS
- Cranial nerve palsies
- meningeal pattern of spread
ABx treatment regimen
Should only be administered by doctors familiar with manageent
- 6 months therapy for pumonary TB
- Inital phase- 2 months on four drugs
- Rifampicin, isoniazid, pyrazinamide (dropped after 2 months no effect on slow growing TB), ethambutol (once sensitivityes known) - continuation phase - 4 months on 2 drugs
- rifampicin
- isoniazid
Mnemonic for TB drugs
PRIEST Pyrazinamide Rifampicin Isoniazid Ethambutol STreptomycin
Rifampicin side effects
red/orange pee
hepatitis
enzyme inducer
Isoniazid side effects
hepatitis peripheral neuropahty (cover with pyridoxine)
Pyrazinamide side effects
hepatitis
rash
gout
little effect against slow growing bacteria
Ethambutol side effects
optic neuritis
renal dysfunction
Prevention
Vaccination (BCG)
Public health measures: treatmen/prophylaxis of contacts
Notifiable disease in UK
Risk factors
HIV Alcoholics Immigrants from endemic areas Homelss IV drug sers
granuloma draw
Langhan cells -fusion of epithelial cells
Epitheloid cells- macrophages
Lymphocytes- T cells
central caseating necrosis
