 Linezolid has no clinically significant effect on most Gram-negative bacteria. Pseudomonas and the Enterobacteriaceae, for instance, are not susceptible. In vitro, it is active against Pasteurella multocida, Fusobacterium, Moraxella catarrhalis, Legionella, Bordetella, and Elizabethkingia meningoseptica, and moderately active (having a minimum inhibitory concentration for 90 % of strains of 8 mg / L) against Haemophilus influenzae. It has also been used to great effect as a second-line treatment for Capnocytophaga infections.
