R-MC-3: Prototheca, Yeast, and Bacillus as a Cause of Mastitis

Mastitis in dairy herds can usually be brought under control by following the basic Program of the National Mastitis Council. Two points of this Program involve the use of antibiotics, one to treat clinical mastitis and the other to treat cows at the beginning of the nonlactating period. Antibiotic therapy, without identifying the mastitis causing organisms, is frequently the veterinarian and dairy farmer's first choice of treatment for infected cows. Cases of mastitis that are refractory to any type of treatment occur frequently also (21, 45). Very often, at the Quality Milk Promotion Services (QMPS) laboratories, bacteriological culture of milk samples from those "odd cases of mastitis" yield Mycoplasma bovis, Actinomyces pyogenes, Streptococcus canis (Group G Streptococcus), Prototheca or yeast. Furthermore, some milk samples may culture only Gram-positive Bacillus sp. The objective of this article is to discuss published material and provide new information obtained at the QMPS concerning mastitis caused by Prototheca sp, yeast, and Bacillus sp.