9-5 Antimicrobial agents and microbial resistance con't Flashcards
1
Q
Size of bacterial ribosome vs eukaryote ribosome
A
Bacteria: 70S
Eukaryote: 80S
2
Q
Protein synthesis inhibitors targeting 30S subunit
A
Aminoglycosides and tetracyclines
3
Q
Protein synthesis inhibitors targeting 60S subunit
A
Chloramphenicol Macrolides Lincosamides Streptogramins Oxazolidinones
4
Q
Aminoglycosides
A
- bactericidal, mainly used against gram (-) rods
- initially penetrate bacterial envelope by disrupting LPS in outer membrane
- Examples: streptomycin and gentamicin
- reduced activity at low pH
- anaerobes are intrinsically resistant
5
Q
Resistance to aminoglycosides
A
- enzymatically inactivate drug (modification by phosphorylation, adenylation or acetylation)
- alter drug target (methylation of rRNA or mutation of ribosomal protein)
- alter drug exposure (increased efflux or decreased uptake)
6
Q
Drug used in combination with aminoglycoside
A
B-lactam
7
Q
Tetracycline
A
- bacteriostatic, active vs gram (- or +), mycoplasma and intracellular bacteria
- examples: tetracycline and doxycycline
- binds 30S subunit
8
Q
Drug combination to avoid
A
bacteriostatic and bacteriocidal
9
Q
Resistance to tetracycline
A
- alter drug exposure (efflux pumps)
- alter drug target (ribosome protection proteins - bind to ribosome and displace drug from binding site)
- binds 30s subunit
10
Q
Chloramphenicol
A
- bacteriostatic (but bactericidal vs encapsulated organisms) , broad spectrum and synthetic (antimicrobial not antibiotic)
- bind 50s subunit
11
Q
Resistance to chloramphenicol
A
- enzymatically inactivated (modified by acetyl transferase)
12
Q
Macrolides
A
- bacteriostatic, broad spectrum, mainly against gram (+) but also gram (-) like chlamydia
- examples: erythromycin and azithromycin
13
Q
Lincosamides
A
- bacteriostatic, works against gram (+ and -) anaerobes
- example: clindamycin
- highly associated with C difficile colitis
14
Q
Streptogramins A and B
A
- bacteriostatic individually, bacteriocidal when taken together
15
Q
Resistance to Macrolids, Lincosamides and Sptreptogramin B (MLSb)
A
- ribosome methylated leading to resistance caused by 40 different erm genes
- erm expression can be either constitutive (always on) or inducible (selectively on or off)
- inducible clindamycin resistance detected using D test (area of inhibition looks more like a D than a circle)
