Which generation of cephalosporins (a class of beta-lactam antibiotics) is known for having antipseudomonal activity, specifically against Pseudomonas aeruginosa?

MCQ Assessment: Antipseudomonal Activity of Cephalosporins

This MCQ is problematic and requires revision because both 3rd generation (specifically ceftazidime) AND 4th generation cephalosporins possess antipseudomonal activity, making two answers technically correct.

The Core Issue

Third Generation Cephalosporins with Antipseudomonal Activity

• Ceftazidime and cefoperazone are 3rd generation cephalosporins with documented activity against Pseudomonas aeruginosa 1
• Among 3rd generation agents available in the United States, ceftazidime is the most active against P. aeruginosa, significantly more so than cefoperazone 2
• Ceftazidime is "presently the most active cephalosporin available against Pseudomonas aeruginosa" among 3rd generation agents 3
• The FDA label explicitly lists Pseudomonas aeruginosa as a susceptible organism for ceftazidime across multiple infection types 4

Fourth Generation Cephalosporins Also Have Antipseudomonal Activity

• Cefepime (4th generation) has broader spectrum activity than 3rd generation cephalosporins and is effective against P. aeruginosa 1
• Fourth generation agents maintain antipseudomonal coverage while adding activity against AmpC-producing organisms 1

Why This Creates Confusion

The question asks which generation is "known for" antipseudomonal activity, but this phrasing is ambiguous:

• If interpreted as "which generation FIRST introduced" antipseudomonal activity → Answer C (3rd generation) is correct
• If interpreted as "which generation HAS" antipseudomonal activity → Both C and D are correct
• The parenthetical "(ceftazidime)" in option C suggests the question writer knows only specific 3rd generation agents have this property, not all 3rd generation cephalosporins

Clinical Context from Guidelines

Guidelines consistently distinguish between "antipseudomonal" and "non-antipseudomonal" 3rd generation cephalosporins 1:

• Non-antipseudomonal 3rd generation: cefotaxime, ceftriaxone, ceftizoxime
• Antipseudomonal 3rd generation: ceftazidime, cefoperazone
• Antipseudomonal 4th generation: cefepime

Guidelines specifically recommend "antipseudomonal cephalosporin" for severe pneumonia with P. aeruginosa risk factors, which includes both ceftazidime (3rd gen) and cefepime (4th gen) 1

Recommendation for MCQ Revision

The question should be rewritten to avoid ambiguity. Better alternatives include:

1. "Which specific 3rd generation cephalosporin is known for antipseudomonal activity?" (Answer: ceftazidime)
2. "Which generation of cephalosporins FIRST introduced antipseudomonal activity?" (Answer: 3rd generation)
3. "All of the following cephalosporins have antipseudomonal activity EXCEPT:" (listing non-antipseudomonal agents)

The current format creates a "trick question" that tests semantic interpretation rather than clinical knowledge, which is poor assessment design for medical education.