Growth of Salmonella During Sprouting of Alfalfa Seeds Associated WithSalmonellosis Outbreaks

Growthof Salmonella During Sprouting of Alfalfa Seeds Associated with SalmonellosisOutbreaks

D.S.Stewart, K.F. Reineke, J.M. Ulaszek, and M.L. Tortorello

Journalof Food Protection, Vol. 64, No 5, 2001, Pages 618-622

Growth of Salmonella was assessed during sprouting of naturally contaminatedalfalfa seeds associate with two outbreaks of salmonellosis.  Salmonellawas determined daily in sprouts and sprout rinse water samples by a three-tubemost probable number (MAN) procedure and a commercial enzyme immunoassay (EIA). Growth of Salmonella in the sprouts was reflected in the rinse water, and theMPNs of the two samples were generally in agreement within approximately 1 log. The results from EIA testing of sprouts and water samples were also inagreement.  The pathogen was present in the seed at less than 1 MAN/g, andit increased in number to maximum population levels of 102 to 103MAN/g in one seed lot and 102 to 104 MAN/g in the otherseed lot.  Maximum populations of the pathogen were apparent by day 2of sprouting.  These results show the ability of the pathogens to grow todetectable levels during the sprouting process, and they provide support for therecommendations to test the sprout water for the presence of pathogens 48 hafter starting seed sprouting.  The effectiveness of a 10-min, 20,000-ug/ml(ppm) calcium hypochlorite treatment of the outbreak-associated seeds wasstudied.  For both seed lots, the hypochlorite treatment caused areduction, but not elimination, of Salmonella contamination in the finishedsprouts.  These results confirm the need to test each production batch forthe presence of pathogens, even after 20,000 ug/ml (ppm) hypochlorite treatmentof seeds, so that contaminated product is not distributed.