The incidence of organisms of the Salmonella group in wild rats and mice in Liverpool

Abstract

In a few instances outbreaks of food poisoning have been traced with a high degree of probability to rodents (Savage & White, 1925; Salthe & Krumwiede, 1924; Jones & Wright, 1936), but in the main the idea that such outbreaks may be due to contamination of food with the excreta of rats and mice is based on the fact that organisms of the Salmonella group have frequently been found in the faeces or organs of these animals. Savage & Read (1913–14) made cultures from the spleen, liver, heart blood and intestinal contents of forty-one rats after enrichment in liquid media and isolated five strains of Bacterium enteritidis (Gaertner). Savage (1918) obtained four strains of what he regarded as “para-Gaertner” which failed to ferment dulcitol and one strain of Gaertner's bacillus from forty-eight rats by direct inoculation from the spleen and heart blood on to MacConkey's medium. Savage & White (1922) from the spleen, liver, heart blood and intestinal contents of ninety-six rats recovered six strains of Gaertner's bacillus. Kerrin (1928) isolated eleven strains of Bact. enteritidis (Gaertner) from 100 rats. His observations were made on the liver and spleen with preliminary enrichment in brilliant green peptone water and subsequent plating on MacConkey's medium. All these British observations agreed in indicating that Gaertner's bacillus was not uncommonly found in wild rats, but in a much more extended series reported from America by Meyer & Matsumura (1927) twenty-eight strains of Bact. enteritidis (Gaertner) and thirty of Bact. typhi murium (Bact. aertrycke) were isolated from 775 rats. These workers inoculated large portions of liver, spleen and colon into broth containing brilliant green and gentian violet and subcultured on brilliant green eosin agar. Verder (1927), who examined 114 rats in another part of America, records the isolation of five strains of Gaertner's bacillus and one of Bact. aertrycke.