ABX III- protein synth inhib

Question 1

what does the small rRNA subunit do?

and the large?

Answer 1

small (30s): has decoding function– it reads the mRNA
large (50s): form the A and P sites for the amino-acid bearing tRNA. it has the peptidyl transferase function (links the aa onto the nascent protein) and also has theexit tunnel through which the growing peptide chain passes out of the ribosome

Question 2

effect of prot synth inhib on bacteria?

Answer 2

inhibits growth but doesn’t kill them– bacteriostatic EXCEPT aminoglycosides be at low concentrations they cause misreading of mRNA leading to incorporation of wrong aa into nascent prot —> cell death

Question 3

all prot synth inhibs are bacteriostatic except…

Answer 3

aminoglycosides, which at small concentrations cause misreading of mRNA leading to incorporation of wrong aa into nascent prot —> cell death

Question 4

Aminoglycosides
mech:
use:
adverse effects:

Answer 4

Aminoglycosides
mech: binds 30 s at decoding site —> at low conc: incorporation of incorrect aa
at high conc: inhibits prot synth
use: serious ifxns with GNR (including P. aeruginosa
used in combo with cell wall synth inhibs for serious ifxn with some GP bact (Staph, enterococcus, A/B strep and Listeria but NOT S. pneumoniae)

streptomycin = used for M. Tb
adverse effects: can be sig – ie limit use to serious ifxn, nephrotoxicity (usually reversible), ototoxicity (common, often reversible), neuromuscular blockade

Question 5

aminoglycosides mech:

Answer 5

mech: binds 30 s at decoding site —> at low conc: incorporation of incorrect aa
at high conc: inhibits prot synth

Question 6

aminoglycosides use:

Answer 6

use: serious ifxns with GNR (including P. aeruginosa
used in combo with cell wall synth inhibs for serious ifxn with some GP bact (Staph, enterococcus, A/B strep and Listeria but NOT S. pneumoniae)

streptomycin = used for M. Tb

Question 7

aminoglycoside adverse effects:

Answer 7

adverse effects: can be sig – ie limit use to serious ifxn, nephrotoxicity (usually reversible), ototoxicity (common, often reversible), neuromuscular blockade

Question 8

tetracyclines
mech:
use:
advers Rxns:

Answer 8

tetracyclines
mech: binds 30s t A site, blocks aminoacyl-tRNA binding

use: Staph, Strep and enteric GNRs
advers Rxns:

atypical orgs: Mycoplasma pneumoniae, borrelia burgdorferi, chlamydia species, ricketsia species, ehrlichia chafeensis
anaplasma phagocytophilum

glycylcyclines are effective agst MRSA and VRE and are reserved for such resistant orgs

adverse Rxns:
well tolerated, but GI upset common and BAD FOR GROWING TEETH (avoid in pregnant women and children under 8)

Question 9

tetracyclin mech

Answer 9

mech: binds 30s t A site, blocks aminoacyl-tRNA binding

Question 10

tetracyclin uses

Answer 10

Staph, Strep and enteric GNRs
advers Rxns:

atypical orgs: Mycoplasma pneumoniae, borrelia burgdorferi, chlamydia species, ricketsia species, ehrlichia chafeensis
anaplasma phagocytophilum

glycylcyclines are effective agst MRSA and VRE and are reserved for such resistant orgs

Question 11

tetracycline adverse Rxns

Answer 11

adverse Rxns:

well tolerated, but GI upset common and BAD FOR GROWING TEETH (avoid in pregnant women and children under 8)

Question 12

chloramphenicol
mech:
use:
adverse Rxns

Answer 12

chloramphenicol
mech: blocks 50 S at A site and transpeptidation site, blocking transpeptidation

use: rarely in dvpd nations, used for Typhoid fever (salmonella typhi), bacterial meningitis, ricketsia species and anaerobic bacteria

adverse Rxns: uncommon but sig toxicity limits, hematopoietic suppression (minor - severe/death), most often hemolytic anemia (suppression of RBCs), gray- baby syndrome due to reduced drug excretion in neonates can be fatal

Question 13

chloramphenicol mech

Answer 13

mech: blocks 50 S at A site and transpeptidation site, blocking transpeptidation

Question 14

chloramphenicol use

Answer 14

use: rarely in dvpd nations, used for Typhoid fever (salmonella typhi), bacterial meningitis, ricketsia species and anaerobic bacteria

Question 15

chloramphenicol adverse rxns

Answer 15

adverse Rxns: uncommon but sig toxicity limits, hematopoietic suppression (minor - severe/death), most often hemolytic anemia (suppression of RBCs), gray- baby syndrome due to reduced drug excretion in neonates can be fatal

Question 16

lincosamides
mech
use
adverse rxns

Answer 16

lincosamides
mech: binds 50s at A and P binding site/blocks transpeptidation

use: infection with anerobes, TSS and necrotizing fasciitis (in combo with cell wall inhib)
second line monotherapy forstaph and strep

adverse rxns: can be sig– limits use to serious rxns, C diff is associated with pseudomembranous colitis

Question 17

lincosamides

mech

Answer 17

lincosamides

mech: binds 50s at A and P binding site/blocks transpeptidation

Question 18

lincosamides use:

Answer 18

use: infection with anerobes, TSS and necrotizing fasciitis (in combo with cell wall inhib)
second line monotherapy forstaph and strep

Question 19

lincosamides adverse rxns:

Answer 19

adverse rxns: can be sig– limits use to serious rxns, C diff is associated with pseudomembranous colitis

Question 20

macrolides
mech:
use:
adverse rxns:

Answer 20

macrolides

mech: binds 50 s exit tunnel, blocking elongation of peptide
use: Resp tract Ifxn bc good activity agst Strep, Staph, Haemophilus, bordetella pertussis, legionella pneumophila and chlamydia ifxns

adverse rxns: well tolerated, some GI upset, reversible cholastic hepatitis

Question 21

macrolides

mech:

Answer 21

macrolides

mech: binds 50 s exit tunnel, blocking elongation of peptide

Question 22

macrolides use:

Answer 22

use: Resp tract Ifxn bc good activity agst Strep, Staph, Haemophilus, bordetella pertussis, legionella pneumophila and chlamydia ifxns

Question 23

macrolides adverse rxns:

Answer 23

adverse rxns: well tolerated, some GI upset, reversible cholastic hepatitis

Question 24

Mechanisms of acquired Abx resistance

Answer 24

1. inactivation of ABX (drug destruction via lactamases, or drug modification by enzymes that modify drug to reduce affinity to target)
2. Change in the target (mutate genes at Abx target/acquisition of new genes that alter/replace target)
3. efflux of abx (pump abx out of bact,)