Gram positive: unreliable against Staphylococci, Bacillus anthracis.

Gram negative: Pseudomonas, Enterobacteriaceae, Neisseria, Haemophilus, Moraxella, Pasteurella.

Anaerobes: not reliable

Other: atypicals including Legionella

Does not cover: most gram positives including Streptococci, Enterococci; Stenotrophomonas, anaerobes