5 – Antimicrobials Flashcards
1
Q
How do antibiotics work?
A
- Attack physiological processes or structures unique to bacteria
o Cell wall
o Cell membrane
o Nucleic acid synthesis, metabolism and organization
o Protein synthesis
2
Q
How do bacteria resist antibiotics?
A
- Decreased permeability (prevent entry)
- Active efflux (pump out)
- Enzymatic degradation/alteration (destroy)
- Target modification (disguise)
- Alternate pathways (do something else)
- Resistance by absence (lacking target)
- *INTRINSIC or GAIN GENETIC COMPETENCE
3
Q
Minimum inhibitory concentration (MIC)
A
- Minimum drug concentration that will INHIBIT an organism’s growth
4
Q
Minimum bactericidal concentration (MBC)
A
- Minimum drug concentration that will KILL an organism
5
Q
Bacteriostatic
A
- When MBC > 4x MIC
6
Q
Bactericidal
A
- When MBC <(=) 4x MIC
7
Q
Concentration dependent drugs
A
- Relies on maximally exceeding organism MIC at site of infection
o may be able to give 1 or 2 big doses/day
8
Q
Time dependent drugs
A
- relies on how long (% of day) drug concentrations exceeding organism MIC are maintain at site of infection
o may require multiple doses/day
9
Q
Beta-lactams
A
- cell wall synthesis INHIBITORS
o transpeptidases and carboxypeptidases - superfamily of antimicrobials
- Beta-lactam/inhibitors combinations
o Act by irreversibly binding to the serine catalytic site of certain bacterial beta-lactamases (NOT all beta-lactamases can be INHIBITED)
10
Q
CEPHALOSPORINS
A
*as increase generation, improvement against Gram-negatives and increasing resilience to beta-lactamases
11
Q
Other beta-lactams
A
- Very broad spectrum
- Most Gram-positive, negative and anaerobes
- Example
o Ertapenem
No activity against enterococci or Pseudomonas
o Monobactams
Only gram-neg activity - Including against Pseudomonas aeruginosa
o Carbapenems
12
Q
TETRACYCLINES
A
- Broad spectrum agents
o Gram-positive activity more limited than Gram-negative
o Resistance is common (susceptibility testing is essential) - *increase in lipophilicity
o Better cross the membrane
Higher concentrations intracellularly and sequestered sites
13
Q
(FLURO) QUINOLONES
A
- Inhibits DNA gyrase and topoisomerase IV
- Prevents replication and organization (supercoiling) – bactericidal
- *at very high drug concentrations, the drugs can prevent the transcription of important activities=decreased drug activity
14
Q
AMINOGLYCOSIDES
A
- Bind to 30S ribosomal subunit
- Also effects ETC, DNA metabolism and cell membrane
- BACTERICIDAL
- *only aerobic bacteria
- Often paired with beta-lactams which will break down the cell wall so they can enter
15
Q
MLSBK
A
- Reversible binding to 50S ribosomal subunit
- *BACTERIOSTATIC
16
Q
PHENICOLS
A
- *reversible binding to 50S ribosomal subunit
- BACTERIOSTATIC
17
Q
Folate synthesis inhibitors
A
- PABA to go into cycle and becomes an INACTIVE intermediate=pathway shuts down
o Competitive inhibition - Diaminopyrimidines
o Directly inhibits the enzymes
18
Q
Nitroimidazoles (Metronidazole)
A
- Low molecular weight
- Readily enters cells
- ONLY KILLS ANAROBES: Under anaerobic conditions: metronidazole is reduced
o Intermediate compounds include unstable free radicals
Radicles bind to DNA and prevent synthesis - BACTERICIDAL
- Banned in food animals
19
Q
Pharmacodynamics
A
- Interactions of a drug with its target, mechanisms of action and correlation of actions with effects
o Ex. Drug-Bug interactions
20
Q
Pharmacokinetics
A
- Process of absorption, distribution, metabolism and excretion of a drug.
o How the compound moves through the body
o Ex. Host-Drug interactions
