Infectious Disease AS Flashcards
What are the different stages of TB?
Primary TB
Primary Progressive TB
Latent TB
Secondary TB
What is Primary TB
Childhood or naive TB infection.
- Organisms multiples @ pleural surface (Ghon focus)
- Macros take TB to LNs ( Nodes + lung lesion = Ghon complex).
- Mostly asymptomatic: may –> fever + effusion
- Cell mediated immunity/ DTH control infection in 95%.
(Fibrosis of Ghon complex –> calcified nodule (Ranke complex). - Rarely may –> primary progressive TB (immunocompromised).
Primary Progressive TB?
- Resembles acute bacterial pneumonia
- Mid and lower zone consolidation, effusions, hilar LNs.
- Lymphohaematogenous spread –> extrapulmonary
Latent TB?
Infected but no clinical or x-ray signs of active TB
Non-infectious
May persist for years
Weakened host resistance –> Reactivation
Secondary TB?
- Usually reactivation of latent TB due to decreased host immunity.
- May be due to reinfection
- Typically develops in the upper lobes
- Hypersensitivity –> tissue destruction –> cavitation and formation of caseating granuloma.
What are the pulmonary features of TB?
Cough, sputum Malaise Fever, night sweats, weight loss Haemoptysis Pleurisy Pleural effusion Aspergilloma/mycetoma may form in TB cavities
Features of meningitis TB?
Headache, drowsiness Fever Vomiting Meningism Worsening over 1-3 weeks CNS - Papilloedema - CN palsies
What are the lymph- node features of TB?
- Cervical lymphadenitis: scrofula
- Painless neck mass: no signs of infection (cold).
What are the genito-urinary features of TB?
Frequency, dysuria, loin/back- pain, haematuria, sterile pyuria.
What are the other involved systems in TB?
Bone TB: vertebral collapse and Pott’s vertebra
Skin: Lupus vulgaris (jelly-like nodules)
Peritoneal TB: abdominal pain, GI upset, ascites
Adrenal: Addison’s disease
What is the diagnosis of latent TB?
Explain the investigation results and interpretation
- Tuberculin Skin Test/Mantoux test
<6mm = negative - no significant hypersensitivity (previously unvaccinated individuals may be given BCG).
6-15 mm = Positive - hypersensitive to tuberculin. Should not be given BCG. May be due to previous TB infection.
> 10mm = positive result = implies previous exposure. Need erythema and induration.
> 15mm - Strongly positive - suggests TB infection.
- If +ve –> IGRA (for prior exposure)
Interferon Gamma Release Assay - Pt lymphocytes incubated with M.tb specific antigens. IFN-y production if previous exposure.
- Either active or latent TB.
- Will not be positive if just BCG (uses M.bovis)
e.g Quantiferon Gold.
Used when mantoux is positive, people where a tuberculin test may be falsely negative.
Tests for Active TB
All patients with suspected TB require a HIV test. Often pushed into active disease by immunosuppression.
- CXR
- Upper lobe cavitation
Active TB
* Sputum samples (Acid fast bacilli will be seen)
* Culture (GOLD STANDARD TEST)
* sputum smear and stain : Stain Ziehl Neelson
Latent TB
* Tuberculin tests (Montoux test) -> Shows active/latent/BCG vaccinated
If the patient has not had the BCG vaccine then this test can be used.
* Inteferongamma release assay (IGRA) -> Shows active/latent
This is used if the patient has had the BCG vaccine. The titre levels of this tells us if the TV has been treated. ,
What would give a false positive in the Mantoux test?
BCG, other mycobacteria, previous exposure.
What would give a false negative in the Mantoux test?
Immunosuppression.
Miliary TB Sarcoidosis HIV Lymphoma Very young age (< 6 months)
What is the pre-assessment investigations of TB?
NB: manage without culture if clinical picture is consistent with TB.
- Continue even if culture results are negative.
- Stress importance of compliance
- Check FBC, liver, renal function
- Creatine Clearanc 10-50ml/min –> decreased R dose by 50% ,avoid E.
- Test visual acuity and colour vision
- Give pyridoxine throughout management.-> This is because Isonazid has a chance to cause peripheral neuropathy
Therefore check LFTs cos all are hepatotoxic, test U+E for electrolyte disturbance + elevation of creatinine.
Baseline visual assessment for ethambutol for vision.
FBC baseline - assess for platelets.
Do not need URine dip.
What is the initial phase of management (RIPE)
Last 2 months
- Rifampicin: hepatitis, orange urine, enzyme induction.
- Isoniazid (nerves = ice for ice): hepatitis, peripheral sensory neuropathy, decrease PMN. (+ pyridoxine). Due to Vit B6 deficiency.
- Pyrazinamide: arthralgia (CI: gout, porphyria)
- Ethambutol: Optic neuritis.
All are hepatotoxic
don’t forget Pyridoxine
What is used in the continuation phase in TB?
4 months
- Rifampicin and Isoniazid
Management of TB Meningitis?
RIPE: 2 months
RI: 10 months
± dexamethasone
What is the management of latent TB?
RI For 3 months
or
Iso (+ pyridoxine) for 6 months.
What is directly observed therapy in TB?
- 3x a week dosing regimen may be indicated in certain groups
- Homeless people with active TB
- patients who are likely to have poor concordance
- all prisoners with active or latent TB.
What are the other TB disease?
Leprosy
MAI (Mycobacterium avium-intracellulare infection)
Buruli Ulcer
Fish Tank Granuloma
What is Leprosy/Hansen’s disease?
Pathogenesis
- Transmitted via nasal secretions (not very infectious)
- M.leprae
What are the classifications of leprosy? 2
Tuberculoid
- Less severe (paucibacillary)
- Th1 mediated control of bacteria
- Anaesthetic hypopigmented macules
- Symmetrical nerve involvement
Lepromatous
- Weak Th1/2 –> Multibacillary
- Skin nodules
- Nerve damage (esp ulnar and peroneal)
- Asymmetrical nerve involvement
What are the clinical features of Leprosy?
- Hypopigmented, insensate plaques (slow over 5 years).
- Trophic ulcers
- Thickened nerves (nerve damage + reduced sweating). Neuropathy + disfigurement.
- Keratitis