Antimicrobial activity of three investigational oral cephalosporins (BK-218, cefdinir, and RU29246) against Legionella.

Three new, orally administered cephalosporins (BK-218, cefdinir, RU29246) were tested against 13 representative strains of Legionella. Cefdinir was most active [50% minimum inhibitory concentration (MIC50), 1 micrograms/ml], a potency comparable to the reference drug cefixime and eightfold less active than erythromycin. BK-218 was the least active cephalosporin (MIC50, 8 micrograms/ml) or 100-fold less potent than rifampin. These investigational cephems appear poorly suited by activity assays for Legionellosis therapy.