Single vs Multiple Antibiotics in Community-Acquired Pneumonia

By Richard G. Wunderink, MD, FCCP; and Grant W. Waterer, MBBS, FCCP

Single vs Multiple Antibiotics for CAP Due to Other Microorganisms

As already mentioned, comparative antibiotic studies for Chlamydia, Mycoplasma, and Legionella do not exist. At least in vitro, macrolides and quinolones are equally efficacious and have no known beneficial effect when used in combination. Therefore, use of both antibiotic classes in a patient with CAP is redundant. For S aureus, the issue is appropriate antibiotics, especially with recent findings of community-acquired methicillin-resistant S aureus pneumonia.¹³

In contrast, combination therapy does appear warranted in patients who have documented Gram-negative bacilli as the causative etiology of CAP. Feldman et al²³ have demonstrated that the mortality rate associated with Klebsiella CAP is lowered by a cephalosporin/aminoglycoside combination. Pseudomonas aeruginosa can also cause CAP. Extrapolation of recommendations for ventilator-associated pneumonia would suggest a benefit for combination therapy, although the data supporting these recommendations are weak. Even the more unusual Acinetobacter CAP appears to be treated more effectively with combination therapy.²⁴

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