Cephalosporin pharmacology — identifying generations in clinical microbiology Which one of the following agents is correctly classified as a third-generation cephalosporin used for serious gram-negative infections?

Introduction / Context:
Cephalosporins are grouped into generations that broadly correlate with antimicrobial spectrum and beta-lactamase stability. Correctly identifying the generation helps choose empiric therapy and anticipate coverage against Enterobacterales, Pseudomonas, and gram-positive cocci.

Given Data / Assumptions:

• The question asks for a third-generation cephalosporin.
• Options include agents from multiple generations.
• We assume standard, widely taught classification used in medical microbiology.

Concept / Approach:
Third-generation cephalosporins (for example, cefotaxime, ceftriaxone, ceftazidime) have enhanced gram-negative activity compared with first and second generations. Cefoxitin is a cephamycin (second generation); cephalothin and cephalexin are first generation; ceftaroline is fifth generation with MRSA activity via PBP2a binding.

Step-by-Step Solution:
List canonical third-generation drugs: cefotaxime, ceftriaxone, ceftazidime, cefixime.Match each option to its generation: cefotaxime (third), cefoxitin (second/cephamycin), cephalothin (first), cephalexin (first), ceftaroline (fifth).Select the correct third-generation agent: cefotaxime.

Verification / Alternative check:
Drug formularies and standard texts categorize cefotaxime as a parenteral third-generation cephalosporin used for meningitis, sepsis, and pneumonia due to susceptible organisms.

Why Other Options Are Wrong:
Cefoxitin is second generation (good anaerobe activity). Cephalothin and cephalexin are first generation (primarily gram-positive). Ceftaroline is fifth generation (covers MRSA), not third.

Common Pitfalls:
Confusing cefoxitin (second) with ceftazidime (third). Also assuming all later-lettered agents are later generation, which is not a safe rule.

Final Answer:
Cefotaxime.