Salmonella typhimurium infections transmitted by chlorine-pretreated clover sprout seeds

Raw seed sprouts have caused numerous outbreaks of enteric infections. Pres oaking seeds in a 20,000 mg/liter (ppm) calcium hypochlorite solution befor e sprouting is recommended to reduce bacterial contamination and infection risk. In 1999, the authors investigated an outbreak of Salmonella serotype Typhimurium infections in Colorado. In a case-control study, they matched 2 0 cases with 58 controls by age, sex, and telephone prefix; 10 (52%) of 19 cases and no controls recalled eating raw alfalfa-style sprouts in the 5 da ys before the patient's illness (p < 0.00001). Traceback implicated clover sprouts grown from seeds shared by two sprouters. The time period and regio n over which these sprouts were sold matched the occurrences of 112 culture -confirmed illnesses. Only one of the sprouters presoaked seeds as recommen ded, and fewer infections were attributable to this sprouter (0.29 vs. 1.13 culture-confirmed infections/50-pound (110.1-kg) bag of seed). After recal l of the implicated sprouts and seed, S. Typhimurium illnesses declined. Co ntaminated raw clover sprouts can cause outbreaks of enteric illness. Preso aking contaminated seeds in a 20,000 mg/liter calcium hypochlorite solution reduces, but does not eliminate, the risk of infection. Until safer produc tion methods are developed, persons eating raw sprouts continue to risk dev eloping potentially serious gastrointestinal illness.