How do cephalosporin generations differ in Gram-negative coverage?

• A. Later generations (3rd–5th) expand Gram-negative coverage and activity against resistant organisms, with varying activity against Gram-positive.
• B. First generation has the broadest Gram-negative coverage.
• C. All generations have identical Gram-negative coverage.
• D. Fourth generation loses Gram-negative activity.

Answer: (A)

As cephalosporins progress through generations, their Gram-negative coverage generally increases and their activity against resistant Gram-negative organisms improves. Early generations are strong against Gram-positive cocci but have limited Gram-negative activity. Moving to the third, fourth, and fifth generations, agents gain potency against a broader range of Gram-negative bacteria, including many that are harder to treat due to resistance mechanisms. At the same time, Gram-positive activity becomes more variable across generations; first-generation drugs have robust Gram-positive coverage, while later generations can show reduced Gram-positive activity, though some newer agents add Gram-positive activity in specific areas (for example, MRSA coverage with certain fifth-generation drugs). This combination—expanded Gram-negative coverage with evolving Gram-positive activity—explains why later cephalosporin generations are described as broadening Gram-negative activity and targeting resistant organisms, with varying effects on Gram-positive activity.