Survey of Bulk Tank Milk using Blood-Esculin Agar Counts 1.

Milk from bulk tanks of 2,931 dairy herds were sampled and evaluated using trypticase blood-esculin agar, somatic cell, standard plate and preliminary incubation counts. Percent samples with trypticase blood-esculin agar counts >1 × 102 colony forming units/ml by organisms were Staphylococcus aureus , 33; Staphylococcus spp., 84; Streptococcus agalactiae , 47; esculin-positive streptococci, 72; coliforms, 73; and other microbes, 89. Trypticase blood-esculin agar counts were useful for identifying primary bacterial contaminants. Correlations were low between trypticase blood-esculin agar counts of specific bacterial groups and somatic cell, standard plate and preliminary incubation counts.