Mycoplasma bovoculi infection increases ocular colonization by Moraxella ovis in calves.

To determine whether infection with Mycoplasma bovoculi increases ocular colonization of cattle eyes with Moraxella bovis and other bacteria, colonization of ocular gram-negative bacteria were measured in eyes of cattle infected with Mycoplasma bovoculi. Strains of Moraxella ovis were chosen because these are among the most commonly isolated species of gram-negative bacteria from cattle eyes. Five strains of M ovis were characterized biochemically and by pilus structure, permitting the recognition of 2 biotypes. All strains were tested in a mouse corneal pathogenicity model. One strain of each biotype was selected for testing in calves. All 5 strains were apathogenic for mice, and the 2 strains tested in cattle did not induce keratitis. Infection of calves with Mycoplasma bovoculi increased the amount and persistence of colonization with the strains of M ovis.