Studies in the Differentiation between Human and Animal Pollution by means of Faecal Streptococci

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Abstract
The isolation of faecal streptococci from the excreta of man, cattle and sheep was investigated. The methods compared were (a) heat, (b) tetrathionate, (c) tellurite, (d) thallium salts. The tellurite method proved highly efficient, isolating 97% of strains from human, cow and sheep faeces. A survey of the properties of strains isolated was made. Differential tests based on (a) heat resistance and (i) reducing properties were devised; these divided the streptococci isolated by the tellurite method into groups, some of which were characteristic of the source. The information available seems capable of distinguishing many strains obtained from man from those derived from cows or sheep, and it is suggested it may be of use in tracing sources of pollution in water, milk and other foodstuffs.