Selective pre-enrichment of Salmonella from eggs by siderophore supplements

Salmonella can overcome the iron limitation of iron-limited nutrient media and albumen by utilizing the siderophores ferrioxamine E and G und grow. 14 out of 18 food-poisoning Salmonella strains of different serotypes stored in hen's egg albumen (approx. 2 organisms/ml) could be detected after 6 h of pre-enrichment with buffered peptone water supplemented with ferrioxamine G (1 microgram/ml) on selective nutrient media. In contrast, only 4 of these Salmonella strains could be reisolated without supplementation. E. coli strains cannot be supplied with iron by ferrioxamines E and G. Therefore, Salmonella enteritidis phage type 4/6 could be isolated in great numbers from mixed cultures with E. coli kept in albumen. Buffered peptone water supplemented with ferrioxamine G also permitted a successful reisolation of Salmonella enteritidis from artificially contaminated eggs. Ferrioxamines E and G function as selective growth factors to enhance sensitivity in the isolation of Salmonella in other nutrient media, too.