LITMUS MILK REACTION AS A DISTINGUISHING FEATURE BETWEEN STREPTOCOCCUS FAECALIS OF HUMAN AND NON-HUMAN ORIGINS

Abstract

More than 90% of 1618 cultures of Streptococcus faecalis obtained from plants, wild animals, and insects produced a soft, reduced, rennet-like curd which underwent stratiform digestion in litmus milk, or else produced no reaction. Cultures of human origin produced a reduced, hard, acidic curd which sometimes was followed by acid-proteolytic digestion. Ten percent of the cultures commensal in nature fermented lactose in litmus milk to produce the hard, acidic curd which sometimes underwent acid-proteolytic digestion. One-third of this group of organisms failed to follow the typical pattern of fermentation by S. faecalis of human origin, that is fermentation of melezitose but not of melibiose. It is suggested that for cultures obtained during analytical procedures the reaction in litmus milk and the fermentation of melezitose and melibiose may be employed to distinguish between contamination representing recent pollution of human origin and the presence of S. faecalis as a member of the microflora of plants with no sanitary significance.