J.L. Watts

Etiological agents of bovine mastitis

A total of 137 microbial species, subspecies and serovars have been isolated from the bovine mammary gland. Nucleic acid hybridization studies have restructured the classification of many mastitis pathogens. Availability of defined species descriptions has permitted greater insight into the distribution and pathogenicity of many previously unrecognized microorganisms associated with bovine mastitis. Precise epidemiological studies are needed to better delineate the role of some microorganisms in bovine mastitis and to aid development of improved control methods.

A comparison of the STAPH-ident and STAPH-Trac systems to conventional methods in the identification of staphylococci isolated from bovine udders

The STAPH-Ident and STAPH-Trac systems (Analytab Products, Plainview, N.Y.) were compared to conventional methods for identification of staphylococci isolated from bovine udders. The STAPH-Ident system identified 80.5% of isolates correctly. An additional 7.6% of Staphylococcus hyicus strains were delineated from S. epidermidis by characterizing acetoin and pigment production. Final accuracy of the STAPH-Ident system was 88.1%. The STAPH-Trac system identified 66.1% of isolates. Negative phosphatase tests for 42.3% of S. hyicus strains resulted in misidentification as S. simulans. Consequently, only 45.5% of S. hyicus isolates were identified correctly by the STAPH-Trac system. Minor modification of each system would permit accurate, rapid identification of staphylococci isolated from bovine udders.

A case study of Streptococcus group G infection in a dairy herd

In this paper an outbreak of bovine mastitis in a dairy herd caused by Streptococcus group G is described. Initial identification of the organism as Streptococcus agalactiae was based upon hemolysis, esculin reaction, and CAMP reaction observed on blood agar used for bulk milk analysis. Initial therapy with a penicillin-containing, lactating cow product cured 24.4% of all streptococcal infections. Definitive serogrouping by coagglutination determined that the majority of infections were due to a weakly-hemolytic, esculin-negative Streptococcus group G. Treatment with a cephalosporin, lactating cow product was only moderately successful (54.9%). Dry-cow therapy with 300 mg cephalosporin eliminated 69.5% of refractory infections. Animals remaining infected following dry-cow therapy were culled. Histopathological study of parenchymal tissue in the lower portion of infected quarters revealed mild damage and slight involutionary changes, whereas, deep parenchymal areas appeared relatively unaffected.

Evaluation of a rapid inoculum standardization system for antimicrobial susceptibility testing of bacterial isolates from the bovine mammary gland

A commercially available rapid inoculum standardization system (RISS) was compared to the broth inoculum standardization method (BIS) for antimicrobial susceptibility testing of bacterial isolates from the bovine mammary gland. Overall agreement between RISS and the BIS method was 95.9%. RISS bypasses the 2-8 h incubation period required by BIS, thus providing antimicrobial susceptibility test data in a more timely manner. RISS was determined to be an acceptable alternative method to the BIS method for preparation of standardized inoculum for antimicrobial susceptibility testing of bovine mammary gland isolates.