Antibiotics

Exceptions include tilmicosin, gamithromycin, and tulathromycin where the spectra are characterized as broad and include Mannheimia haemolytica and Pasteurella multocida, as well as the above mentioned gram-negative bacteria.

Bacteroides fragilis strains are moderately susceptible to macrolides.

Macrolides are active against atypical mycobacteria, Mycobacterium, Mycoplasma, Chlamydia, and Rickettsia spp but not against protozoa or fungi.

In vitro synergism is seen with cefamandole (against Bacteroides fragilis), ampicillin (against Nocardia asteroides), and rifampin (against Rhodococcus equi)