Tuberculosis Flashcards
(35 cards)
Who must you notify if TB is suspected?
- Public health
Notifiable disease under Public health act 1984 - TB nurse specialists (support patient
in investigation, during treatment, public health
issues and initiate contact tracing)
What is it?
Tuberculosis (TB) is a chronic, communicable respiratory disease, caused by the bacteria Mycobacterium tuberculosis
Where is it common?
Africa, Asia and Latin America
Mycobacterium tuberculosis features and stain used for them
- bacillus
- waxy coating that makes gram staining ineffective- theres resistance to acids used in staining (describes as acid fastness)
- require a special staining technique using the Zeihl-Neelsen stain
Risk factors for TB
- Known history of TB contact
- Born in a country with high TB incidence
- Foreign travel to country with high incidence of TB
- Immunocompromised state
- Homelessness
- Drug use and alcoholism
- HIV
Risk factors for reactivation
18% of world population have latent TB
Immunosuppressive state
- HIV infection
- Substance abuse
- Prolonged Corticosteroid therapy
- Solid Organ transplant
- TNF-a antagonists
- Haematological malignancy
- Severe kidney disease
- DM
- Low BMI/ malnutrition
How does transmission occur?
Transmitted via droplet transmission- infective dose is between 1 and 10 bacilli (Small dose needed to infect)
Coughing, sneezing
Contagious but not easy to acquire infection, need prolonged exposure= 8hrs/day up to 6 months
Is latent TB contagious?
No
Primary and Post Primary TB are contagious
How long does it take for TB to reproduce and what does it require to reproduce ?
Obligate aerobe
Long generation time=15-20hrs
How does infection occur in the lungs ? pathophysiology
- Inhaled aerosol
- macrophages engulf bacteria and initiatecell mediated immunity
- release ofInterferon-γ and cytokines activates more macrophages
- releasereactive oxygen species (ROS)
- epithelioid macrophages and Langhans giant cells form granulomas with central cessation(caseous necrosis) = this is called a tubercle
Primary complex formed = Ghon’s focus and draining local lymph nodes
How many people get Primary active TB and when does this happen?
Only 5% of people infected will get primary active TB when the primary complex doesn’t heal and progresses
If you dont get primary active TB what happens
Latent TB
Most people with latent infection will self-cure (90%) with or without calcification of the primary complex
Reactivation of latent TB is possible and occurs when host immunity is compromised (5%)- granuloma fails and bacilli will spread= Post primary TB
Where does re-activation occur and why there ?
Reactivation occurs in upper lung zones (apices) due to high O2
Symptoms of TB
- Tiredness/malaise
- Weight loss (weeks to months)
- Feverwith nocturnal sweats (typically drenching)
- Cough– dry or productive
- Haemoptysis
- Crackles on auscultation
Investigation in suspected TB?
- CXR if atypical but suspect pul TB do CT chest
- 3 early morning samples of sputum- In productive cough
- Consider bronchoscopy if no productive cough and pul TB suspected
- Histology of lymph nodes
- Bloods esp. LFT’S, Vit D levels and a HIV test
- Pleural effusion → pleural aspiration and pleural biopsy (biopsy- high yeid)
What to look for on CXR? in primary and miliary
Primary active or post primary- patchy solidlesions or cavitated solidlesions orstreaky fibrotic flecks ofcalcification
Miliary TB- multiple discreet small nodules throughout the lungs
Bihilar lymphadenopathy
What investigation would you do from the sputum?
Ziehl-Neelsenstaining -AAFB (alcohol-acid-fast bacilli)
TB Culture and sensitivity- can take 6-8 weeks - more sensitive than stain only
Mycobacterium Tuberculosis PCR- faster than culture
NAAT
How to test for latent TB? 2 types
QuantiFERON test
TuberculinorMantoux skin test
How does the Quantiferon test work?
- Blood sample from pt uses their lymphocytes to culture them with antigens from Mycobacterium tuberculosis
- If there’s been previous exposure to the bacteria T lymphocytes will produce interferon gamma
How does the Mantoux test work?
- Tuberculin protein from mycobacteria injected intradermally
Which test is more specific to infection with Mycobacterium Tb
Quantiferon
Mantoux
- will give false positives if exposed to other mycobacterium or BCG vaccine
- If host immune response compromised will get false negative
Treatment ?
- Rifampicin(6 months)
- Isoniazid(6 months)
- Pyrazinamide(2 months)
- Ethambutol(2 months)
- Vitamin D
Surgery- if lung grossly damaged
Rifampcin side effects ?
hepatitis (3rd hepatotoxic)
orange urine or tears
thrombocytopaenic rash (rash due to low platelet count)
Lots of drug interactions like warfarin and OCP
Isoniazid side effects ?
- hepatitis (2nd most hepatotoxic)
- Rashes
- peripheral neuropathy
- psychosis.
