**Core Concept:** Extended-spectrum beta-lactamase (ESBL) is an enzyme produced by some bacteria which inactivates beta-lactam antibiotics like penicillins, cephalosporins, and monobactams. This leads to resistance in these antibiotics and makes treatment difficult.

**Why the Correct Answer is Right:**

The correct answer is **D:** Ceftolozane/tazobactam. Ceftolozane is a beta-lactam antibiotic that is resistant to ESBL enzymes, while tazobactam is a beta-lactamase inhibitor that neutralizes the effect of ESBL enzymes on ceftolozane, making the combination effective against ESBL-producing bacteria.

**Why Each Wrong Option is Incorrect:**

A. Ceftriaxone (Option A) is a broad-spectrum cephalosporin that is susceptible to ESBL enzymes. Therefore, it is not the drug of choice for treating ESBL organisms.

B. Ceftazidime (Option B) is also a cephalosporin that is susceptible to ESBL enzymes. Similar to Option A, it is not the optimal choice for treating ESBL organisms.

C. Meropenem (Option C) is a carbapenem antibiotic, which is resistant to ESBL enzymes. However, it is a broader-spectrum antibiotic and may not be as effective as the combination therapy with ceftolozane/tazobactam.

**Clinical Pearl:**

Combination therapy with beta-lactamase inhibitors like tazobactam is preferred for treating infections caused by ESBL-producing bacteria. This is because it helps to preserve the activity of beta-lactam antibiotics against ESBL enzymes, leading to more effective treatment and reduced risk of treatment failure.

**Correct Answer:** Ceftolozane/tazobactam (Option D) is the drug of choice for treating infections caused by ESBL-producing bacteria. It provides a synergistic effect, making the antibiotic active against the bacteria while inhibiting the beta-lactamase enzymes produced by the bacteria.