Incidence and germicide sensitivity of Salmonella typhi and Vibrio cholerae O1 in alfalfa sprouts

The prevalence of some enteric bacteria in alfalfa sprouts obtained from public markets and supermarkets in Queretaro City was determined In addition, the antimicrobial effect of several commercial germicides was tested on alfalfa sprouts for reduction of native coliforms and inoculated Vibrio cholerae O1 or Salmonella typhi. Escherichia coli and Salmonella sp. were detected in 74% and 1.1% of 90 of samples, respectively, and no sample tested positive to V. cholerae O1. Coliforms ranged from 7.3 to 8.5 log(10) CFU/g. Treatment of alfalfa sprouts with 200 mg/L of hypochlorite, of a commercial iodophor, or of chlorine dioxide, or with 100 mg/L of Citricidal(R) for 5 min, reduced native coliforms only by 1-2 log(10) CFU/g. Reductions of S. typhi and V. cholerae O1 with 200 mg/L of sodium hypochlorite and 100 mg/L Citricidal(R) were also no more than 1.5 log(10) CFU/g. Sprouts from seeds contaminated with V. cholerae O1 that were irrigated daily with water containing 100 mg/L chlorine dioxide, showed significantly lower V. cholerae O1 counts than seeds irrigated with tap water (p<0.05). However, V. cholerae O1 persisted after 8 days of sprouting, when the sprouts are ready for marketing. Treatment of seeds and sprouts with antimicrobials does not appear to be effective for reducing pathogens to safe levels.