Update on Preenrichment and Selective Enrichment Conditions for Detection of Salmonella in Foods

Abstract

The search for short and sensitive cultural methods for detection of Salmonella in foods has met with limited success. Short (3–8 h) incubation of non-selective enrichment media do not provide conditions for effective resuscitation of stressed or injured salmonellae and result in unacceptably high numbers of false-negative results. Isolation of Salmonella is not dependent on the nutritional value of preenrichment media; simple media such as lactose and nutrient broths are equally reliable as highly nutritive sterility testing media. The need for detergents in non-selective enrichment of fatty foods and use of preenrichment transfer volumes greater than 1 ml is not indicated. Although selective enrichment in tetrathionate brilliant green (TBG) broth at an elevated temperature (43 C) increases method sensitivity, use of Mueller-Kauffman TBG under similar analytical conditions may be inhibitory to Salmonella. Refrigeration of preenrichment and selective enrichment broth cultures has been used successfully to provide greater analytical flexibility by increasing the number of days on which analyses can be initiated without engendering weekend work.