MOR

Question 1

MOR of beta lactams

Answer 1

destruction of beta lactamase enzymes, alteration of PBPs, and decreased permeability of outer cell membrane in gm - bacteria

Question 2

MOR of vancomycin

Answer 2

VRE and VRSA: due to modification of D-Ala-D-Ala binding site by expression of vanA (to d-lactate), which prevents the binding of vanc to bacteria

VISA: due to thickening of the peptidoglycan layer of the cell wall, restricting access of vanc into its site of activity

Question 3

MOR of Synercid

Answer 3

alteration of ribosomal binding site, due to picking up the erm gene, which wipes out ALL drugs that bind to the 50S ribosomal subunit

Question 4

MOR of oxazolidinones

Answer 4

alteration of ribosomal subunit target site (rare) and cross resistance between linezolid and tedizolid

Question 5

MOR of daptomycin

Answer 5

rarely reported; altered cell membrane binding through loss of a membrane protein

Question 6

MOR of lipoglycopeptides

Answer 6

same as vanc, except only affects tela and dalbavancin. oritavancin still maintains activity

Question 7

MOR of FQs

Answer 7

alteration of binding sites lead to decreased binding affinity of the FQs, expression of active efflux, and alteration in cell wall permeability that doesn’t allow FQ to get into the porins and leads to decreased FQ accumulation within the cell (esp pseudomonas!); cross resistance between FQs

Question 8

MOR of macrolides

Answer 8

active efflux (mef gene): pumps out of cells and confers low level resistance to macrolides; alteration in the binding site: (erm gene) erm codes for methylation of the macrolide 50S binding site, which leads to low-affinity binding of macrolides (high level resistance to ALL macrolides AND clinda and synercid that bind to 50S subunit)

cross resistance between macrolides also occurs

Question 9

MOR of aminoglycosides

Answer 9

alteration in aminoglycoside uptake: leads to decreased penetration of aminoglycoside inside bacteria

synthesis of aminoglycoside-modifying enzymes: modified aminoglycoside displays poor uptake through the outer membrane and binds poorly to ribosomes (high level resistance)

alteration in ribosomal binding site (rare)

Question 10

MOR of tetracyclines

Answer 10

1. decreased accumulation of tetracycline within bacteria due to altered permeability or the presence of efflux pumps (that pump away from 30S)
2. decreased access of the tetracycline to the ribosome due to the presence of ribosomal protection proteins
3. enzymatic inactivation of the tetracycline
4. cross resistance between tetracyclines (except minocycline)

Question 11

what tetracycline can maintain susceptibility against organisms of resistance?

Answer 11

minocycline

Question 12

what lipoglycopeptide can maintain susceptibility against organisms of resistance?

Answer 12

oritavancin

Question 13

MOR of tetracycline analogues

Answer 13

retain activity against many tetracycline resistant bacteria because they do NOT appear to be affected by the 2 major tetracycline resistance mechanisms (efflux and ribosomal protection); they can still be resisted due to enzymatic inactivation of tetracycline

Question 14

MOR of Bactrim

Answer 14

1. bacterial resistance is mediated by point mutations in dihydropteroate synthase and/or altered production oro sensitivity of bacterial dihydrofolate reductase
2. resistance appears more slowly in combo product
3. resistance has been reported in ecoli, h flu, staph

Question 15

MOR of polymyxins

Answer 15

alteration of outer cell membrane: decreased lipopolysaccharide content, reduction in calcium and magnesium content, decreased outer membrane proteins
cross resistance between polymyxin B and colistin!

Question 16

MOR of clinda

Answer 16

alteration of the ribosomal binding site

Question 17

MOR of metronidazole

Answer 17

altered growth requirements and altered levels of ferredoxin