Mastitis Pathogen Identification, Plates, Media, and Costs

Abstract

There are available to the veterinarian a variety of microbiological media for the cultivation of bacteria associated with infectious processes. Even within the more restricted area of bovine mastitis there are a number of selective and differential microbiological media, some of which are included in commercially available kits. The practitioner wishing to do his own microbiology must carefully evaluate each of the media so that meaningful and accurate results are obtained.

Many bacteria have at one time or other been implicated as causative agents of infectious mastitis. From a bacteriological standpoint, the veterinarian doing his own culturing should attempt to recognize only the more common of these. The organisms in this category would include Streptococcus agalactiae (beta hemolytic streptococcus), Staphylococcus aureus, Escherichia coli, Klebsiella and perhaps Corynebacterium pyogenes and Streptococcus uberis. For organisms which are sporadically involved or re-quire specialized media, e.g. Mycoplasma, assistance of other laboratories should be sought.

It is commonly accepted that the gram-positive cocci, including Staphylococcus aureus, Streptococcus agalactiae, Streptococcus uberis and Streptococcus dysgalactiae, comprise the most important group of mastitis pathogens. As previously mentioned S. aureus and Str. agalactiae are of primary importance.

Coliform mastitis characterized by acute inflammation of the mammary gland, with high fever, diarrhea, shock, and frequently death is commonly associated with an environmental source of the organisms. Enterobacter and E. coli are frequently associated with unsanitary conditions where fecal material is thought to be the major source of the organisms. Recently, Klebsiella mastitis has been associated with the use of sawdust for bedding.

Corynebacterium pyogenes mastitis is characteristically a chronic sporadic disease in which the milk frequently has a foul odor, which results from the presence of an anaerobic gram-positive coccus along with C. pyogenes.