A microbiology technologist is performing a b-lactamase test on a staphylococci isolated from a hospitalized patient.The test was negative, so the technologist reported out in vitro antimicrobial susceptibility test results for b-lactam antibiotics.After 2 days, the patient was not improving and the physician changed the patient's antibiotic to an aminoglycoside.The patient showed improvement immediately.Why was the b-lactamase test on the staphylococci negative, when the organism produced b-lactamase?
A)The test was a false negative-the organism really did produce b-lactamase, but it did not react with the test.
B)Staphylococci must be exposed to the b-lactam agent before it will produce a positive test result.
C)The test was a false positive-the organism reacted with the test, but it did not produce a b-lactamase.
D)The staphylococci on the plate were more than 24 hours old and false-negative test results can occur when an "old" organism is used.

Question

Quizplus · Accepted Answer

Production of b-lactamase in staphylococci is inducible, and exposure to an inducing agent (a b-lactam agent) is often required to obtain enough concentrations of the enzyme for detection with conventional b-lactamase tests.

A Microbiology Technologist Is Performing a B-Lactamase Test on a Staphylococci