Tuberculosis (Cut Off for Exam 1) Flashcards
1
Q
Transmission
A
- Transmitted by “droplet nuclei”
- Dependent on source infectiousness, environment of exposure, closeness/duration, # inhaled of organisms, host immune status
- 1 “active” disease patients infects ~1 person/month
2
Q
Phases of Infection
A
- Primary
- LTBI (latent tuberculosis infection)
- Active (“re-activation”) tuberculosis disease
3
Q
Primary Infection
A
- Inhalation of bacilli
- Bacilli ingested by pulmonary macrophages and evade immune system and multiple within macrophages
- Release of bacilli causes tissue necrosis
- Body granulomas to contain and prevent further extension of the necrotic lesion
- “Latent” phase of infection has begun
4
Q
LTBI
A
- Bacteria live in body without making patient sick (dormant)
- Evidence of infection: TST (positive skin test), reactive IFN-gamma release assay (Quanti-FERON Gold, T-SPOT)
- Normal chest X-ray, negative sputum AFB smears, and negative culture
- Patients aren’t contagious
- Treatment is part of TB elimination strategy in US
- 5-10% will develop active TB
5
Q
Active TB Disease
A
- “Re-activation”
- Onset may be gradual
- Productive cough lasting >3 weeks, chills, fever, night sweats, etc.
- Patients become sick and are able to spread disease again
- Inflammatory response can result in necrosis and structural collapse
6
Q
Diagnosis
A
- Physical examination
- Positive TST or blood test (Quanti-FERON Gold)
- Abnormal chest radiograph - often seen in apical segments of upper lobes
- Positive sputum smear or culture
7
Q
Antituberculosis Drugs
A
- R: Rifampin (RIF), Rifabutin, Rifapentine
- I: Isoniazid (INH)
- P: Pyrazinamide (PCA)
- E: Ethambutol (EMB)
8
Q
Additional Antituberculosis Drugs
A
- Injectables: streptomycin, amikacin
- Quinolones: Moxifloxacin
- Cycloserine
- P-aminosalicylic acid
- Ethionamide
9
Q
Treatment Principles for LTBI
A
- Active disease should be ruled out FIRST
- Monotherapy may be used ONLY for LTBI
- Risk of isoniazid-resistance is low and low disease burden
- Delay treatment during pregnancy
10
Q
Treatment Regimens for LTBI
A
- Isoniazid & Rifapentine: once weekly for 3 months
- Rifampin: Daily for 4 months
- Isoniazid: daily for 9 or 6 months (latter used for HIV and children >= 2 y.o.)
11
Q
LTBI + INH
A
- Only 40-60% who initiate 9 month INH therapy complete it
- Poor adherence
- Long treatment duration
- Toxicity
12
Q
3HP + DOT Advantages
A
- Higher completion rates
- Shorter duration
- Less hepatotoxicity
- Given once weekly
- Newer studies shown effectiveness in patients 2-17 y.o., HIV on ART, not receiving DOT
13
Q
DOT
A
- Directly Observed Therapy
- Health care worker watches patient swallow each dose
- Consider for most patients
- Intermittent therapy: facilitates supervision, improves outcomes
- DOT can lead to reductions in relapse and drug resistance
- Use DOT with other measures to promote adherence
14
Q
Treatment Principles for Active Disease
A
- Patient should be isolated until no longer infectious
- Empiric therapy has multiple drugs: helps cover and prevent drug-resistant, de-escalate once susceptibilities are known
- Duration is dependent on: host factors, extent of disease, and presence of resistance
- Never add a single drug to a failing regimen
15
Q
Treatment Adherence
A
- Long treatment duration (6 mo to 2-3 years)
- Non-adherence is a major problem
- Single most important factor in treatment failure
- Leads to resistance
