Stimulation of Streptococcus thermophilus growth in mastitic milk

Abstract

SummaryGrowth of Streptococcus thermophilus was faster in mastitic milk, aseptically collected following intramammary infusion of Escherichia coli endotoxin, than in normal aseptically collected milk. The contribution of polymorphonuclear leucocytes (PMN), of plasma and plasmin to this stimulation has been investigated. Addition of plasmin to low cell count milk stimulated growth of the streptococcus to the same degree as mastitic milk. However, addition of plasma or PMN from blood or from milk were less stimulatory. The part played by these components in providing casein breakdown products for the weakly proteolytic Str. thermophilus in mastitic milk is discussed.