INF1 - A. TB-COVERED Flashcards
what causes TB and what is it
mycobacterium tuberculosis (rod-shaped bacteria)
infection which affects the lungs (can also occur in other organs and joints)
what caused the increase in cases of TB from 1980
drug resistance and HIV (more likely to get if have HIV - leading cause of death in those with HIV)
what is latent TB
- the bacteria is present but the person doesn’t have any symptoms
- the immune system produces inflam that surrounds the TB bacteria and walls off the infection in the lungs
- can develop TB later if their immune system in weakened
- screening before drug treatment - ie. infliximab
what is the Mantoux test
identifies if someone has TB infection or has had the BCG vaccine
how does the Mantoux test work
- liquid with tuberculin injected intradermally under skin
- site checked 48-72 hours later
- +ve result (>15mm) = previous exposure to tuberculin protein, bigger the reaction, more likely they are infected
- antibodies against TB cause immune response which causes a skin reaction of a raised red bump
how is TB transmitted
- close contact with people with active TB
- airborne transmission (droplets)
- only TB of throat/lungs is infectious
- requires prolonged contact
how does TB cause infection
- bacteria enters the lungs, travels to alveoli and multiples
- TB develops slowly, can take months for symptoms to show
- bacteria can enter bloodstream - spread to joints etc
TB risk factors
country of birth
travel history - latent TB then travel?
previous TB contact
immunosuppression
living conditions
social risk factors
how does the BCG vaccine work
- contains live attenuated mycobacterium
- doesn’t offer lifelong protection
- can protect against development of severe forms of disease ie - TB meningitis
- limited impact in spread of pulmonary TB
- small scar left at injection site
- recommended for children at high risk and healthcare workers
signs and symptoms of pulmonary TB
productive cough (possibly with blood in mucus) lasting for more than 3 weeks
very tired
fever
night sweats
loss of appetite
weight loss
enlarged lymph nodes
crackles in lungs
how to diagnose TB
- x-ray = detects lesions in tissue
- ultrasound = detects peripheral lesions
- echocardiogram = TB can cause congestive heart failure
- CT = whole body TB
- samples of mucus for culture and sensitivity testing (antibiotics)
- Mycobacteria can take a very long time to grow therefore start treatment
what to do when infection is confirmed
- inform household contacts and those with a cumulative contact of 8> hours in last 3 months
- Mantoux test for household and non-household contacts >5 yrs
- IGRAs blood test for TB infection
- chest x-ray to detect latent/active TB
what is the treatment of latent TB
Rifampicin + isoniazid for 3 months OR
Isoniazid for 6 months
(HIV patients - also use HAART to minimise risk of active disease)
how to treat patients who don’t have risk factors for MDR-TB
isolated in single room until completed 2 weeks treatment
wear mask if leaving room
what is the standard treatment of active TB
- 2 months of isoniazid (with pyridoxine), rifampicin, pyrazinamide, ethambutol INITIAL PHASE
- 4 months of isoniazid (with pyridine) and rifampicin CONTINUOUS PHASE
(CNS involvement/drug resistance can be up to a year of treatment)
how often is the medication taken
daily dosing or 3 times weekly dosing
why is the treatment so long
mycobacteria grow slowly and dormant bacteria divide only when threatened by antibiotic treatment
so 6 months allows active and dormant bacteria to be eliminated
what is DOT
improves adherence by using HC workers, community volunteers or family members to observe and record patients taking each dose
(those who don’t adhere to treatment, drug/alcohol misusers, homeless, prisoners, MDR-TB)
why are so many drugs taken
prevents resistance and eradicates bacteria in different environments
mutated bacteria are unlikely to be resistant to 2 drugs as drugs work in different ways
how does isoniazid work
- inhibits mycolic acid synthesis
- bactericidal against actively dividing mycobacteria
- metabolised in liver by CP50 enzymes (slow acetylators more susceptible to neuropathy)
- pyridoxine for prophylaxis of peripheral neuropathy
counselling on isoniazid
N&V, jaundice (liver)
peripheral neuropathy
take before food
how does rifampicin work
bactericidal against those that multiply in macrophages or closed caseous lesions
liver enzyme inducer therefore increased metabolism of other drugs (INTERACTIONS)
counselling on rifampicin
take before food
interactions
colours body fluids orange and contact lenses
N&V, jaundice
rashes
bruise easily
how does pyrazinamide work
bactericidal
most effective against actively dividing intracellular organisms
