Experimentally Induced Coliform Mastitis: Inoculation of Udders with Serum-Sensitive and Serum-Resistant Organisms

Abstract

SUMMARY Acute or peracute mastitis developed in 15 of 15 normal lactating quarters of cows given serum-resistant ( sr ) coliform bacteria. Of these 15 quarters, 11 were given doses of 6 × 10 2 colony-forming units ( cfu ) or less, and, doses greater than 10 5 cfu . Of 9 sr organism-inoculated quarters with a polymorphonuclear neutrophil leukocyte ( pmn ) count of greater than 300,000/ml. in 0-hour strippings milk, 5 did not respond and 4 develped acute to peracute mastitis. Serum-sensitive ( ss ) organisms inoculated into 16 normal lactating quarters 8 quarters were given inoculums containing less than 10 2 cfu ; 5, 3 × 10 2 to 3 × 10 3 cfu ; and 3, greater than 10 6 cfu ) did not grow or produce evidence of inflammation in 12 quarters and produced only mild and transient inflammation in 4 quarters. Of the latter 4 quarters, 3 had been given massive doses (greater than 10 6 cfu ) in attempts to break the barrier to growth of the inoculum. The resulting inflammation was considered to be caused mainly by the physical presence alone of endotoxin of the initial dose. Of 6 ss organism-inoculated quarters with 0-hour pmn count of greater than 300,000/ml., 4 did not respond, and 2 responded with mild, transient mastitis, again due to a massive dose of inoculum (greater than 10 6 cfu ). Leukocyte-free quarters were equally susceptible to mastitis caused by sr organisms and were not susceptible mastitis caused by ss organisms regardless of whether the quarters had been previously exposed to the same or different strains of the bacteria.