Isolation of Mycoplasma californicum from an outbreak of bovine mastitis and the experimental reproduction of the disease.

A mycoplasma-like organism was isolated from five cows with chronic incurable mastitis from one dairy herd. This organism was shown to be Mycoplasma californicum and was used to infect three cows by intramammary inoculation. The challenge organism was reisolated from all the infected quarters and the ensuing inflammatory response produced a chronic mastitis with a permanent drop in milk yield. Antibiotic treatment in one animal was unsuccessful.