INF1 - A. TB-COVERED

Question 1

what causes TB and what is it

Answer 1

mycobacterium tuberculosis (rod-shaped bacteria)
infection which affects the lungs (can also occur in other organs and joints)

Question 2

what caused the increase in cases of TB from 1980

Answer 2

drug resistance and HIV (more likely to get if have HIV - leading cause of death in those with HIV)

Question 3

what is latent TB

Answer 3

• 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

Question 4

what is the Mantoux test

Answer 4

identifies if someone has TB infection or has had the BCG vaccine

Question 5

how does the Mantoux test work

Answer 5

• 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

Question 6

how is TB transmitted

Answer 6

• close contact with people with active TB
• airborne transmission (droplets)
• only TB of throat/lungs is infectious
• requires prolonged contact

Question 7

how does TB cause infection

Answer 7

• 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

Question 8

TB risk factors

Answer 8

country of birth
travel history - latent TB then travel?
previous TB contact
immunosuppression
living conditions
social risk factors

Question 9

how does the BCG vaccine work

Answer 9

• 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

Question 10

signs and symptoms of pulmonary TB

Answer 10

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

Question 11

how to diagnose TB

Answer 11

• 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

Question 12

what to do when infection is confirmed

Answer 12

• 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

Question 13

what is the treatment of latent TB

Answer 13

Rifampicin + isoniazid for 3 months OR
Isoniazid for 6 months
(HIV patients - also use HAART to minimise risk of active disease)

Question 13

how to treat patients who don’t have risk factors for MDR-TB

Answer 13

isolated in single room until completed 2 weeks treatment
wear mask if leaving room

Question 13

what is the standard treatment of active TB

Answer 13

1. 2 months of isoniazid (with pyridoxine), rifampicin, pyrazinamide, ethambutol INITIAL PHASE
2. 4 months of isoniazid (with pyridine) and rifampicin CONTINUOUS PHASE

(CNS involvement/drug resistance can be up to a year of treatment)

Question 13

how often is the medication taken

Answer 13

daily dosing or 3 times weekly dosing

Question 13

why is the treatment so long

Answer 13

mycobacteria grow slowly and dormant bacteria divide only when threatened by antibiotic treatment
so 6 months allows active and dormant bacteria to be eliminated

Question 14

what is DOT

Answer 14

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)

Question 14

why are so many drugs taken

Answer 14

prevents resistance and eradicates bacteria in different environments
mutated bacteria are unlikely to be resistant to 2 drugs as drugs work in different ways

Question 14

how does isoniazid work

Answer 14

• 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

Question 15

counselling on isoniazid

Answer 15

N&V, jaundice (liver)
peripheral neuropathy
take before food

Question 16

how does rifampicin work

Answer 16

bactericidal against those that multiply in macrophages or closed caseous lesions
liver enzyme inducer therefore increased metabolism of other drugs (INTERACTIONS)

Question 17

counselling on rifampicin

Answer 17

take before food
interactions
colours body fluids orange and contact lenses
N&V, jaundice
rashes
bruise easily

Question 18

how does pyrazinamide work

Answer 18

bactericidal
most effective against actively dividing intracellular organisms

Question 19

counselling on pyrazinamide

Answer 19

N&V, jaundice (only used in first 2 months) joint pain and swelling

Question 20

how does ethambutol work

Answer 20

bacteriostatic

Question 21

counselling on ethambutol

Answer 21

eyesight checks as can lead to optic neuritis dose reduction if have renal impairment

Question 22

what are combination products

Answer 22

reduce tablet burden and aid compliance 1. Rifater - isoniazid, rifampicin, pyrazinamide Voractive - isoniazid, rifampicin, pyrazinamide, ethambutol 2. Rifinah - isoniazid, rifampicin

Question 23

what is MDR-TB

Answer 23

resistant to at least isoniazid and rifampicin

Question 24

what is XDR-TB

Answer 24

resistant to isoniazid and rifampicin plus a quinolone (ciprofloxacin) plus at least one 2nd line injectable agent

Question 25

risk factors for resistance

Answer 25

history of TB treatment, prior treatment failure contact with known case of drug resistant TB patient from a country with high prevalence of resistant TB (due to no access to meds - can't afford?) HIV infection lack of compliance