Antibiotics

Question 0

50S inhibitors

Answer 0

Linezolid, macrolides, chloramphenicol, clindamycin, quinupristin/dalfopristin

Question 1

30S inhibitors

Answer 1

Amino glycosides and tetracycline

Question 2

Blocks initiation

Answer 2

Linezolid, amino glycoside

Question 3

Blocks elongation

Answer 3

Amino glycosides, tetracycline, macrolides, chloramphenicol, clindamycin, quinupristin/dalfopristin

Question 4

Blocks termination

Answer 4

Amino glycoside

Question 5

Mitochondrial ribosomes

Answer 5

Linezolid, tetracycline, chloramphenicol

Question 6

Linezolid binds what part of ribosome

Answer 6

P site on 50S

Question 7

Oxazolidinones

Answer 7

Mech: binds 23S RNA on 50S unit prevents forming of initiation com
Spec: gram+, MRSA and vanco resistant enterococci
Resis: alterations in 23 rRNA
AdvE: bone marrow suppression, serotonin syndrome if taken with SSRI, hallucinations, increased heart beat, nausea. Linezolid

Question 8

Gentamicin amikacin tobramycin

Answer 8

Amino glycosides - bactericidal mech: prevents formation of initiation complex, causes misread mRNA, induces early termination
Spec: gram neg aerobes (in combo)…intrinsic resis- can’t enter cell = treat with cell wall inhibitor, acquire resis - enzymes that inactivate drugs…amikacin is special to pseudomonas

Question 9

Mechanisms of amino glycosides

Answer 9

Blocks initiation of synthesis
Blocks further translation and elicits premature termination
Incorporates incorrect amino acid
Creates fissures in cell membrane

Question 10

Side effects of amino glycosides

Answer 10

Tubular necrosis: nephrotoxicity- drug held in renal cortex (reversible)
Ototoxicity - vestibular and auditory dysfunction (irreversible)
Pregnancy class D  - hearing loss in fetus

Question 11

Important facts of amino glycosides

Answer 11

Poor absorption - usually administered through IV

Polar and excluded from CSF

Question 12

Concentration dependent killers

Answer 12

Amino glycosides and fluoroquinolones

Question 13

Time dependent killers

Answer 13

Vancomycin and beta lactams

Question 14

Tetracycline mechanism

Answer 14

Prevents attachment of tRNA to A site bacteriostatic

Question 15

Chloramphenicol mechanism

Answer 15

Inhibits peptide bond formation

Question 16

Mechanism of macrolides streptotagims and clindamycin

Answer 16

Inhibit translocation (tRNA moving from A site to P site)

Question 17

The tetracyclines

Answer 17

Tetracycline doxycycline and minocycline

Question 18

Spectrum of tetracycline

Answer 18

Broad at first but due to resistance

B. burgdorferi, h. Pylori, mycoplasma pneumoniae

Question 19

Resistance of tetracycline

Answer 19

Intrinsic - decreased uptake

Acquired - increased efflux, alteration of ribosome target, rarely enzymatic inactivation of drug

Question 20

Adverse effects of tetracycline

Answer 20

Chelates with metal ions decreases absorption
GI irritation and photosensitive
Discoloration of teeth and inhibits bone growth in children
Don’t use during pregnancy class D

Question 21

What is drug persistence? And what bacteria displays this?

Answer 21

Shifts between different genetically homogenous forms depending on presence of drug
Borrelia burgdorferi

Question 22

Spectrum of chloramphenicol

Answer 22

Extended but limited due to severe side effects

Question 23

Resistance to chloramphenicol

Answer 23

Acetyltransferase modifies drug to prevent binding to ribosome

Question 24

Adverse effects of chloramphenicol

Answer 24

TOXIC. Bone marrow depression. Aplastic anemia. Gray baby syndrome

Question 25

Gray baby syndrome

Answer 25

Premature infants lack enzyme UDP-glucuronyl transferase and have decreased renal function so high levels of the drug accumulate which can lead to cardiovascular and respiratory collapse

Question 26

Macrolides, what are they and the mechanism?

Answer 26

Erythromycin, azithromycin and clarithromycin
Bacteriostatic
Inhibit translocation by binding 23S rRNA of the the 50S subunit

Question 27

Spectrum of macrolides

Answer 27

Broad coverage of respiratory pathogens

Chlamydia (single dose)

Question 28

Atypical pneumonia - what causes it and treatment?

Answer 28

Mycoplasma pneumonia
Treat with doxycycline, azithromycin, levofloxacin
Beta lactams are not effective

Question 29

Resistance to macrolides

Answer 29

Methylation of 23S rRNA binding site (associated with clindamycin and quinupristin/dalfopristin resistance)
Increased efflux
Hydrolysis of macrolides by esterases

Question 30

Adverse effects of macrolides

Answer 30

GI
Liver failure, prolonged QT interval
Inhibitors of cyp450 enzymes
Clarithromycin is not safe during pregnancy

Question 31

Mechanism and spectrum of clindamycin

Answer 31

Bacteriostatic - blocks translocation of at 50S ribosomal subunit

Gram positive anaerobic….treat ance

Question 32

Resistance and adverse effects of clindamycin

Answer 32

Mutation of ribosome, methylation of rRNA…cross resistance with macrolides and inactivation by adenylation
Hypersensitivity - rash and fever
Diarrhea, abdominal pain, mucus and blood in stool
Superinfection with C. difficile

Question 33

Streptogramins - what are they and what is their mechanism

Answer 33

Quinupristin/dalfopristin

Combined action can be bactericidal
Bind 50S to inhibit translocation

Question 34

Spectrum of quinupristin/dalfopristin

Answer 34

For infections of multiple drug resistant gram positive bacteria

Question 35

Resistance of quinupristin/dalfopristin

Answer 35

Ribosomal methylase prevents binding of drug to its target
Enzymes can inactivate the drugs
Efflux of proteins that put them out of the cells
Cross resistance with macrolides and clindamycin

Question 36

Adverse effects of quinupristin/dalfopristin

Answer 36

High incidence including arthralgias, myalgias

Inhibits cyp450 enzymes and likely to have significant drug-drug interaction