Antibiotics 1 Flashcards
Chemotherapy
- Eradicate pathogenic organisms or neoplastic cells
- Treatment of infection or cancer
- Based on the principle of selective toxicity
Antimicrobial Activities
- Bactericidal vs. bacteriostatic
- Concentration- and time-dependent effects
- minimal inhibitory concentration (MIC)
- concentration-dependent killing rate (CDKR)
- post antibiotic effect (PAE) - Antimicrobial spectrum
- narrow-; broad-; extended
- combination therapy
□ synergistic, antagonizing - Microbial sensitivity and resistance
- Prophylactic use
Gram Pos
-inner most plasma membrane
-thick peptidoglycan cell wall
-outer capsule
-more easily treatable with antibiotics
-stains purple after gram stain
gram neg
-inner most plasma membrane
-thin peptidoglycan wall
-another plasma membrane
-outer capsule
-harder to treat with antibiotics
-stains pink after gram stain
Microbial Sensitivity & Resistance
1) lots of germs and few are resistant to antibiotics
2) antibiotics kill bacteria causing illness, they also kill good bacteria protecting the body from infection
3) antibiotic resistant bacteria grow and take over
4) some bacteria give their antibiotic resistance to other bacteria, causing more problems
antibiotic prohylaxis
correct:
choice of antibiotics
dose
timing of administration
re-dosing/duration
Folate Inhibitors
- bacteriostatic
dna syn inh - synergistic effects
- TMP-SMX (sulfamethoxazole) - urinary tract, respiratory infection, malaria, toxoplasmosis
- common resistance
- plasmid-mediated
- sulfa insensitive enzyme - side effects
- upset GI
- skin rashes
- light sensitivity
- high risk for hypersensitivity
- risk of blood disorder in chronic use
beta-lactams
- ~cillins; cephalosporins
- Prevent transpeptidation
- binding to PBP
- Bactericidal (⇧sensitivity w. growing cells)
- synergistic effects with protein synthesis inhibitors
- antagonized by bacteriostatic antibiotics
- Spectrum coverage varies
- carbapenems as last resort
- monobactams: G- rods
- Newer drugs aimed at
- β-lactamase resistant
- acid-resistant
- extended-spectrum
- Pharmacokinetic aspects
- water-soluble
- poor GI absorption
- wide distribution (joints, pleural and pericardial cavities, bile, etc.)
- largely tubular secretion
- Prolonged duration of effect by
□ higher doses
□ co-admin of probenecid
□ IM in depot form
- Side effects
- hypersensitivity (rare)
- low cross-sensitivity btw penicillin vs. cephalosporin
- hypersensitivity (rare)
mechanism for beta lactam resistance
- inactivation by β-lactamase
- modification of target PBPs
- impaired penetration; modified porin structures
- increased antibiotic efflux
