Lactose Broth is a recommended non-selective pre-enrichment broth for Salmonella in foods and dairy products. In some cases, Salmonella may be present in low numbers, requiring a pre-enrichment step to grow the organism to detectable levels. Further, various food processing steps may lead to sublethal injury of Salmonella, which subsequently may not be recovered by direct detection methods. Lactose Broth allows for the recovery and growth of these organisms prior to detection. The absence of selective agents reduces stress on the cells.
Lactose Broth is also used for the growth and detection of coliforms, which by definition ferment lactose. The fermentation of lactose produces acid and gas.
Gelatin Peptone and Beef Extract serve as the source of carbon and nitrogen to satisfy growth requirements, and lactose is the carbohydrate source. For further information on which food matrices are recommended for enrichment with Lactose Broth, refer to the FDA’s Bacteriological Analysis Manual (BAM)1 and the USDA’s Microbiology Laboratory Guidebook (MLG)2.