PHENOTYPIC DETECTION OF RESISTANCE

Question 1

what testing detects the presence of beta-lactamase enzymes producing bacterial strains?

Answer 1

beta-lactamase, nitrocefin test

Question 2

what organisms require beta lactamase testing?

Answer 2

-S. aureus
-N. gonorrhoeae
-Moraxella catarrhalis
-H. influenzae

Question 3

what indicates a positive beta-lactamase?

Answer 3

red-orange color
*penicillin and cephalosporin resistance

Question 4

what indicates a negative beta-lactamase?

Answer 4

yellow color
*penicillin and cephalosporin susceptible

Question 5

what organisms are testing for ESBL-producing strains?

Answer 5

Escherichia species
Klebsiella species

Question 6

what method is used to detect ESBL-producing strains?

Answer 6

double-disk synergy method

Question 7

what indicates a positive ESBL test?

Answer 7

zone of inhibition around ceftazidime disk in the direction of the clavulanate disk

Question 8

what indicates a negative ESBL test?

Answer 8

no expanded zone of inhibition

Question 9

what method(s) is used to detect inducible clindamycin resistance in S. aureus?

Answer 9

D- test

Question 10

what indicates a positive D-test (D+)?

Answer 10

blunt, D-shaped zone of inhibition around the clindamycin disk

Question 11

what indicates a negative D-test (noninduction phenotypes)?

Answer 11

clear, circular zone of inhibition around the clindamycin disk

Question 12

what test detects pathogens containing carbapenemase?

Answer 12

modified Hodge test

Question 13

what does the carbapenemase enzyme inactivate?

Answer 13

carbapenem and other beta-lactam antibiotics
*considered CRE

Question 14

what determines a positive CRE test?

Answer 14

E. coli presents with “clover-leaf” indentation in the zone of inhibition

Question 15

what determines a negative CRE test?

Answer 15

no E. coli growth in the disk diffusion zone