Purpose: The purpose of the study was to survey the microbial quality of open refillable bulk soap sampled in three different states and four different food establishment types, and to determine the influence of formulation factors on the degree of contamination.
Methods: Laboratory personnel visited 100 locations in each of three states: Arizona, Ohio, and New Jersey to collect 300 soap samples from public restrooms in convenience stores, fast food restaurants, grocery stores, and sit-down restaurants. Samples were tested for total plate count (TPC), coliforms, pH, percent solids, water activity, and the presence of two common antimicrobial ingredients.
Results: More than 12% of samples contained high level of bacteria (typically > 107CFU/ml) Samples with high TPC tended to have higher coliform counts. Many of the contaminated soaps contained antibiotic resistant organisms. Solids content was correlated with high TPC and all samples with < 4% solids had detectable TPC. More than 16% of samples with no detectible antimicrobial were contaminated, while 8% of samples with triclosan and 3% of samples with chloroxylenol were contaminated. Bacteria were more prevalent in bulk soaps in grocery stores (16.7%) and fast food locations (15.6%) than in sit-down restaurants (9.7%) or convenience stores (3.6%). Little difference in bacterial prevalence between soap in men’s and women's restrooms (P = 0.58) or between states (P = 0.81) was noted.
Significance: Bulk soap dispensers are frequently (> 10%) contaminated with bacteria, often at very high levels (107). Washing hands with bulk soaps in food service facilities may represent a significant, avoidable safety risk, especially to immunocompromised individuals.