ROLE OF LYSOZYME IN KILLING AND LYSIS OF COLIFORM BACTERIA IN THE BOVINE ANIMAL .1. SERUM AND MILK CONCENTRATIONS OF LYSOZYME AND SUSCEPTIBILITY OF COLIFORM STRAINS TO ITS ACTION

Concentrations of lysozyme were determined in 206 bovine sera and 37 bulk-tank milks. Detectable levels were not found in 46.6% or 96 sera, 38.3% (79 sera) had less than 2.5 μg/ml, 12.1% (25 sera) had concentrations of 2.5 to 25 μg/ml and 2.9% (6 sera) had concentrations greater than 25.0 μg/ml. Only one milk sample had any detectable lysozyme (0.5 μg/ml) by the method used. Lysis by bovine sera of washed coliform bacteria previously determined to be resistant or sensitive to killing by bovine serum was tested in various buffer systems. No correlation between killing by serum and sensitivity to lysis by lysozyme was found. EDTA markedly potentiated serum lysis in the presence of added lysozyme. Lysozyme itself was not lytic. Added lysozyme did not potentiate killing of the coliforms by bovine serum when tested by direct plate counts or by spectrophotometric growth assay. These in vitor results suggest that lysozyme may have limited importance as a protective agent against coliform bacteria in vivo. © 1979.