Differential Attachment to Almond and Peanut Seeds by Wild−Type and Mutant Salmonella enterica Serotypes Tennessee and Enteritidis

Attachment is a critical step for bacterial establishment in low-moisture foods and subsequent survival under desiccation conditions. This study assessed the attachment ability of five knock-off mutants, each of S. Tennessee and S. Enteritidis, along with their wild-type parents, to peanut and almond seeds. Sterilized sandy soil (20 g per sample) containing 10⁶ (lower level) or 10⁷ (higher level) CFU/g of lyophilized cells of wild-type and mutant Salmonella were mixed with sterilized peanut (blanched and unblanched) or almond seeds at room temperature for 1 h with mixing. Seeds were subsequently soaked in 5 ml phosphate-buffered saline (PBS) to release attached Salmonella cells at 4 ˚C for 0 or 24 h. The percentages of cells in contaminated sandy soil attached to the seeds were determined. The cells of Salmonella mutants had a significantly (P ≤ 0.05) lower percentage of attachment than those of the wild-types. On average, more S. Tennessee cells attached to blanched than unblanched peanut seeds, especially at the lower inoculation level. Seed soaking time did not significantly affect the release of Salmonella cells from peanut and almond seeds to PBS. The results of the research are useful for developing novel antimicrobial interventions to control Salmonella establishment in low-moisture foods.