Antimicrobials - Mycobacterial Infections Flashcards
mycobacteria -
- stain?
- replication where?
- growth rate?
- acid fast - not gram bc they down have peptidoglycan cell wall - instead they have lipid rich cell wall (mycolic acids)
- inside macrophages - need to get drugs here!
- slow growing - dormancy = challenge bc we like to target fast growing things and mess with growth!
Latent TB infection vs TB disease
- inactive/active multiplying
- Chest X-ray normal/abnormal
- Sputum neg/sputum pos
- No Symptoms/Yes Symptoms
- Not infectious/Infectious b4 tx
- Not a case of TB/Yes a case
Obstacles and solutions when treating TB?
Bad=slow growth, viable but dormant-slow metabolism, rapid resistance, toxicity
Solutions=multiple drug therapy, regularly taken for sufficient time
What to give for drug resistant TB?
streptomycin
- How to get M Avium complex (MAC)?
- What organisms make up MAC?
-M avium and M intracellulare
- ingestion of contaminated food/water
- -> respiratory droplets
Preferred Initial phase of treatment for active TB?
RIPE: Rifampin isoniazid pyrazinamide ethambutol
DAILY 8 weeks of treatment
Preferred continuation phase for active TB?
- Rifampin
- Isoniazid
DAILY OR TWICE WEEKLY-18 weeks of treatment
Alternative regimentS - initial tx for active TB?
- RIPE drugs but dosing different - DAILY FOR 2 WEEKS AND THEN TWICE WEEKLY FOR 6 WEEKS
- RIPE drugs for THRICE WEEKLY FOR 8 WEEKS
Alternative regimentS - continuation phase for active TB:
- RI drugs TWICE WEEKLY FOR 18 WEEKS
- RI drugs THRICE WEEKLY FOR 18 WEEKS
Daily preferred treatment for LATENT TB?
Isoiazid - 9 months Daily or Thrice weekly
best drug for active and latent TB?
isoniazid
Isoniazid
-not MOA but how does it kill stuff?
- bactericidal for actively growing bacilli
- penetrates macrophages - extracellular and intracellular
Isoniazid is less effective against what organisms?
-atypical mycobacterial infections (M avium complex MAC)
Isoniazid MOA:
- inhibits synthesis of mycolic acid –> needed for cell wall
- -> forms covalent bond with at least 2 proteins involved in mycolic acid - impedes function
- prodrug activated by mycobacterial catalase peroxidase enzyme (Kat G)
Isoniazid
- safety?
- absorption?
-safest and most effective anti-mycobacterial drug we have
- readily absorbed from GI tract
- penetrates the CNS and goes everywhere
Primary drug for nearly all therapeutic or prophylactic TB regimens?
-isoniazid
MOA mycobac uses to be resistant to isoniazid?
How to avoid active TB resistance?
- mutation of Kat G pro-drug activation enzyme
- over expression of Inh A protein which is involved in mycolic acid synthesis
-MUST use at least two active antiTB agents!
Slow acetylator patients - issues with isoniazid?
-isoniazid has an acetyl group so if slow acetylator the = peripheral neuropathy
Isoniazid adverse rxns?
-hepatitis: risk inc with age and alcoholics
-peripheral neuropathy - risk inc with slow acetylators, malnourished, alcoholics, diabetics, or AIDS patients
(fixable by giving pyridoxine)
What are the rifamycin drugs used to treat active TB?
- *-rifampin
- *-rifabutin
- rifapentine
Rifampin
- MOA?
- cidal or static?
- penetration?
- inhibits RNA synthesis (transcription) - binds to BACTERIAL DNA dependent RNA polymerase
- CIDAL
- absorbed well from GI -
- penetrates most tissues and phagocytic cells = kills intracellularly too!
Primary and alternative tx for latent TB?
- primary = isoniazid
- alternative = rifampin
Development of resistance to rifampin MOA?
-point mutations in bac RNA poly
–> MUST COMBINE WITH OTHER ANTI TB DRUGS
Rifampin Adverse effects:
- GI issues - nausea, vomit
- Nervous system=headache, dizziness, fatigue
- hepatitis=usually in those with some hidden liver disease and slow acetylators
- RED-ORANGE COLOR in pee, poop, sweat, tears, and saliva
