Growth of Salmonella during sprouting of alfalfa seeds associated with salmonellosis outbreaks

Growth of Salmonella was assessed during sprouting of naturally contaminate d alfalfa seeds associated with two outbreaks of salmonellosis. Salmonella was determined daily in sprouts and sprout rinse water samples by a three-t ube most probable number (MPN) procedure and a commercial enzyme immunoassa y (EIA). Growth of Salmonella in the sprouts was reflected in the rinse wat er, and the MPNs of the two samples were generally in agreement within appr oximately 1 log. The results from EIA testing of sprouts and water samples were also in agreement. The pathogen was present in the seed at less than 1 MPN/g, and it increased in number to maximum population levels of 10(2) to 10(3) MPN/g in one seed lot and 10(2) to 10(4) MPN/g in the other seed lot . Maximum populations of the pathogen were apparent by day 2 of sprouting. These results show the ability of the pathogen to grow to detectable levels during the sprouting process, and they provide support for the recommendat ion to test the sprout water for the presence of pathogens 48 h after start ing seed sprouting. The effectiveness of a 10-min, 20,0000-mug/ml (ppm) cal cium hypochlorite treatment of the outbreak-associated seeds was studied. F or both seed lots, the hypochlorite treatment caused a reduction, but not e limination, of Salmonella contamination in the finished sprouts. These resu lts confirm the need to test each production batch for the presence of path ogens, even after 20,000 mug/ml (ppm) hypochlorite treatment of seeds, so t hat contaminated product is not distributed.