The Use of Bacteriophage for Freeing Protozoal Cultures of Contaminating Bacteria

two organisms with bacteriophage active against the bacterial contaminant. We undertook to carry out the latter procedure. The contaminating bacteria were isolated by plating on agar and identifiedv as belonging to the salmonella group. They fermented glucose, mannite, maltose, arabinose and dulcite with the production of acid and gas; lactose, saccharose, and salicin were not affected. Litmus milk became strongly alkaline; the methyl red test was positive and Voges-Proskauer reaction negative; indole was not produced and the organisms were actively motile. They were agglutinated by Bad. paratyphoid B serum (H & 0) to full titre. Pure H serum in the specific phase was not available for determining* exactly, the identity of the organisms and the strain was provisionally labelled as Salmonella typhi murium (Bact. artrycke). On exposure to the action of bacteriophage, the strain was found susceptible to the action of stock bacteriophage which acted on S. typhi murium strainsPreliminary study showed that, by subjecting the salmonella strain to the action of this bacteriophage, lysis was complete in four hours and that this lysis was maintained for more than three days. A potent phage, therefore, capable of lysing the contaminating bacterial strain, was now available.