In ESBL phenotypic testing, what arrangement is used to observe synergy with clavulanate?

In ESBL phenotypic testing, what arrangement is used to observe synergy with clavulanate?

• A. A clavulanate-containing disk placed near a beta-lactam disk to observe an expanded zone
• B. A single antibiotic disk with a high concentration
• C. Two disks of the same antibiotic
• D. PCR-based detection only

Answer: (A)

In ESBL phenotypic testing, you’re looking for the interaction between a beta-lactam antibiotic and a beta-lactamase inhibitor. ESBL enzymes can destroy many beta-lactams, but they’re inhibited by clavulanate. Placing a disk that provides clavulanate near a beta-lactam disk creates a gradient where clavulanate diffuses toward the antibiotic. If the organism produces ESBL, the inhibitor will suppress the enzyme in the overlapping area, allowing more antibiotic to act and producing an expanded zone of inhibition toward the clavulanate disk. This synergy is the diagnostic signal that an ESBL producer is present. So, the setup with a clavulanate-containing disk placed near a beta-lactam disk to observe an expanded zone best demonstrates this interaction. The other options don’t test this inhibitor-driven synergy: a single high-concentration disk doesn’t reveal ESBL-mediated breakdown; two disks of the same antibiotic don’t show inhibition relief by the inhibitor; and PCR-based detection identifies genes rather than the actual phenotypic response of the organism to the inhibitor.

In ESBL phenotypic testing, you’re looking for the interaction between a beta-lactam antibiotic and a beta-lactamase inhibitor. ESBL enzymes can destroy many beta-lactams, but they’re inhibited by clavulanate. Placing a disk that provides clavulanate near a beta-lactam disk creates a gradient where clavulanate diffuses toward the antibiotic. If the organism produces ESBL, the inhibitor will suppress the enzyme in the overlapping area, allowing more antibiotic to act and producing an expanded zone of inhibition toward the clavulanate disk. This synergy is the diagnostic signal that an ESBL producer is present.

So, the setup with a clavulanate-containing disk placed near a beta-lactam disk to observe an expanded zone best demonstrates this interaction. The other options don’t test this inhibitor-driven synergy: a single high-concentration disk doesn’t reveal ESBL-mediated breakdown; two disks of the same antibiotic don’t show inhibition relief by the inhibitor; and PCR-based detection identifies genes rather than the actual phenotypic response of the organism to the inhibitor.