Antibiotic Resistance

Question 1

minimum inhibitory concentration (MIC)

Answer 1

lowest concentration that inhibits growth

Question 2

minimum bactericidal concentration (MBC)

Answer 2

lowest concentration that kills 99.9% of population

Question 3

susceptible

Answer 3

MIC can be achieved in the body at recommended doses

Question 4

resistant

Answer 4

MIC cannot be achieved

Question 5

drug resistance

Answer 5

usually genotypic changes that are retained in the absence of antibiotic; MIC cannot be achieved

Question 6

tolerance/persistence

Answer 6

transient, dormant variants (not mutants) in the population enabling survival in presence of antibiotic; linked to biofilm formation

Question 7

mechanisms of resistance

Answer 7

1. modification of target so it is insensitive to inhibitor
2. duplication or replacement of target enzyme
3. efflux pumps
4. depression of metabolic agents needed for prodrug

Question 8

class C serine beta lactamases

Answer 8

inhibit all but carbapenems

Question 9

class A & D, serine pencillinases/beta lactamases

Answer 9

first discovered in s. aureus shortly after penicillin was introduced

Question 10

extended spectrum beta lactamases

Answer 10

mutations in penicillinases - resistance to penicillins and cephalosporins; widespread in enterobacteriaceae, pseudomonas, usually plasmid encoded; inhibited by clavulanate

Question 11

clavulanate

Answer 11

beta lactamase inhibitor

Question 12

serine carbapenemases

Answer 12

inhibited by clavulanate

Question 13

class B metallo-beta lactamases (zinc)

Answer 13

cleave all beta lactam antibiotics including carbapenems; inhibited by EDTA but not clavulanate

Question 14

possible beta-lactam resistance mechanisms

Answer 14

beta lactamase enzymes, reduced cell wall permeability, mutations in PBP to prevent beta lactam from binding

Question 15

aminoglycosidase resistance mechanisms

Answer 15

acetylation, methylation, or phosphorylation of 30S subunit

Question 16

anti-folates resistance mechanisms

Answer 16

replacement enzymes

Question 17

tetracycline resistance mechanisms

Answer 17

efflux pumps

Question 18

fluoroquinolones resistance mechanisms

Answer 18

altered gyrase/topoisomerase or efflux pumps

Question 19

elements that mediate antibiotic resistance

Answer 19

plasmids, insertion sequences/transposons, integrons, genetic exchange (conjugation, transformation, transduction)

Question 20

integrons

Answer 20

genetic unit that includes genes of a site-specific recombination system capable of capturing and mobilizing genes contained in mobile elements (gene cassettes)

Question 21

multiple antibiotic resistance

Answer 21

conjugation (cell-to-cell contact) allows transferring of resistance to other organisms