Antimicrobial Agents -Antimycobacterial Flashcards
Out of the mycobacterium, which one is the opportunistic human pathogens?
M. avium-intracellulare complex
What are mycobacterium defined by?
Their unique cell wall–Acid fast
[dense, high lipid, hydrophobic, difficult to penetrate, resistant to dehydration, acids and alkalis]
When do we see meningitis with tuberculosis?
children under 5 in endemic areas
Is mycobacterium tuberculosis an obligate human pathogen?
Yes
Why is it important to distinguish latent TB from active disease?
Treatment for latent TB is different from active disease
[BUT THEY ARE NEITHER SYMPTOMATIC NOR INFECTIOUS]
What is the purpose of whole blood assays for tuberculosis?
- measure the patient’s gamma interferon response to M. tuberculosis specific antigens
- Reduces/removes influence of BCG vaccination–QuantiFERON-TB Gold, T-SPOT.TB
What are the 4 first-line drugs that are considered Anti-TB standard treatment?
- isoniazid
- rifampin
- pyrazinamide
- ethambutol
[take 4 drugs for 2 months, 2 for 4 to 7 months]
Why isn’t streptomycin a 1st line drug for TB?
increased resistance
Why must we use combination therapy to treat active TB?
Drug resistant mutants occur-patients can harbor drug resistant bacteria and then long treatments make them the dominant strain- use more than one drug to avoid this
[10 up 8 is the magic number]
Can latent TB be treated with a single drug?
yes
What TB drugs inhibits cell wall synthesis 2? Disrupts: membrane, energy metabolism? Inhibits mRNA synthesis the prokaryotic beta subunit RNA polymerase?
- Isoniazid, ethambutol
- Pyrazinamide
- Rifampin
Can isoniazid be used as a single drug for treatment of latent TB? What is it activated by?
- Yes
2. It is a prodrug activated by mycobacterial enzyme
resistance to INH occurs in what 2 cases?
- inhA over-expression
2. deletion of KatG
In the case of INH causing peripheral neuropathy, what do you give the patient?
B6
Is rifampin active against rapidly growing or slowly metabolizing bacilli? cidal or static?
Both–bactericidal
How does resistance occur to rifampin?
mutation in rpoB gene
Is Rifampin a p450 inhibitor?
No- P450 inducer [accelerates metabolism]
Is ethambutol active against multiplying bacilli? static or cidal?
- yes
2. bacteriostatic
Ethambutol interferes in the biosynthesis of cell wall arabinogalactan…how is resistance to ethambutol conferred?
Mutations in embB which encodes arabinosyl transferases
T-F—pyrazinamide is a prodrug metabolized via pyrazinamidase (pncA) to pyrazinoic acid
True
MDR TB is resistant to what 2 drugs? What is extensively drug resistant XDR TB?
- Isoniazid and rifampin2. MDR+resistance to fluoroquinolone and 1 of 3 injectables
What are the 3 injectable TB drugswe should know?
amikacin, kanamycin, capreomycin
A low pH renders what drug inactive?
streptomycin
Resistance that is incurred because drugs are exported before it reaches target effects what 3 TB drugs?
- Streptomycin
- Isoniazid
- Ethambutol
What drugs are exceptions to being ineffective when TB is in a dormant non-replicating state?
Rifamycin and fluoroquinone
Alteration of the enzyme that prevents the prodrugfrom becoming active affects which drugs?
pyraziinamide and isoniazid
What are 3 characteristics of how M. Leprae is transmitted?
- droplets through close freq contact.
- host genetic factors effects
- no impacted by aids
Pauci-bacillary leprosy drug regimen?
Multi-bacillary leprosy drug regimen?
- rifampicin and dapsone 6 months
2. rifampicin, dapsone, clofazimine for 12 mo.
What is the regimen for antibiotics for buruli ulcers?
8 weeks rifampicin and streptomycin/amikacin
+surgery
T-f–for the nontuberculous mycobacteria, detection means you have the disease?
False- it is ubiquitous, no person to person spread, opportunistic infections mainly in immunocompromised individuals
M. kansasii, M. simiae and M. marinum are in what group?
Runyon 1 photochromogens
M. scrofulaceum and M. szulgai are in what group?
Runyon 2 scotochromogens
M. avium complex (MAC), M. ulcerans, M. xenopi,
M. malmoense, M. terrae, M. haemophilum and M. genavense are in what group?
Runyon 3- nonphotochromogens
– M. abscessus
– M. chelonae
– M. fortuitum are in what group?
Runyon 4 rapid growers.
What 2 drugs do we use for M. marinum?
Rifampin and ethambutol
What is the suggested drug regimen for MAC?
- clarithromycin or azithromycin
- Rifatubin or rifampin
- ethambutol
MWF 12 mo free of sputum or lifetime treatment
Are drugs used for MTB complex good enough for NTM?
sometimes, but a lot of times resistance has formed
key concepts for NTM-
– Determine species to select the best treatment
– Multi-drug therapy
– Colonization versus pathogen
