More about this research in Agricultural Research.

Bovine Staph, Beware: Test Vaccine Promising Against Mastitis

Bessie will chew her cud in more comfort if early tests pitting a new vaccine against the most stubborn cases of mastitis--those caused by Staphylococcus aureus bacteria--are any indication of its efficacy. The vaccine promises to catch the 50 to 60 percent of staph-caused mastitis cases in the United States that have eluded today’s commercial vaccines.

Agricultural Research Service dairy scientist Albert J. Guidry developed the vaccine with the biotechnology company Nabi in Rockville, Md. Nabi identified a single staph strain, or serotype, that appears to provide the component missing in earlier vaccines.

Guidry and coworkers at ARS’ Henry A. Wallace Beltsville (Md.) Agricultural Research Center formulated this serotype--336--with the two known mastitis serotypes into a vaccine. Large-scale tests to confirm its ability to prevent infection have not yet been done. But it is proving effective at curing intractable mastitis cases when combined with antibiotics, according to studies by Michigan State University veterinary scientist Phil Sears.

Antibiotics are often ineffective against staph because the bacteria have become resistant or they have holed up in places the drugs can’t reach. In Sears’ studies, he cured more than half of infected cows by isolating the causative S. aureus strain from a dairy herd, killing it, then injecting it back into the infected cows a few weeks before administering antibiotics. But this procedure is too cumbersome for commercial use.

The new vaccine solves that problem. And it proved as effective as Sears’ herd-specific vaccine, curing 55 to 60 percent of infected cows. It cleared up staph infections in about 10 percent of infected cows in the herds in Sears’ study--even before he administered antibiotics.

ARS is now looking for a partner in the agricultural arena to fund further testing and develop a commercial vaccine. ARS is the U.S. Department of Agriculture’s chief scientific research agency.

More about this research is in the November issue of Agricultural Research magazine.

Scientific contact: Albert J. Guidry, ARS Immunology and Disease Resistance Laboratory, Beltsville, Md., phone (301) 504-8285, fax (301) 504-9498, aguidry@lpsi.barc.usda.gov.