Refillable Soap Containers Could Spread Bacteria

Jim Kling

May 05, 2011

May 5, 2011 — Bacteria-contaminated bulk-soap refillable hand washing stations may leave significant levels of bacteria on the hands after washing, which could help spread opportunistic pathogens, according to a study published in the May issue of Applied and Environmental Microbiology.

Recent research suggests that 1 in 4 refillable soap dispensers in public bathrooms are contaminated with bacteria. In healthcare settings, several outbreaks have been linked to contaminated soap dispensers. The Centers for Disease Control and Prevention recommend that such dispensers should not be "topped off" by adding additional soap to a partially filled container.

Refillable containers are the most common form of dispenser in community settings such as public restrooms, but little research has been done into the potential effects of contamination.

Carrie A. Zapka, MS, from GOJO Industries, Inc, in Akron, Ohio, and colleagues conducted a study to determine how many bacteria remained on hands after washing with contaminated soap, and how many bacteria could be transferred from the hands to a secondary surface.

In 1 experiment, subjects washed their hands for 10 seconds using 1.5 mL liquid soap. One group used soap that had been contaminated with a high level of Serratia marcescens (7.51 log10 colony-forming units [CFU]/mL), whereas the other used soap with low level of contamination (4.51 log10 CFU/mL). The participants finished with a 10-second rinse.

The high-level contamination group had a mean of 5.28 log10 CFU/hand compared with 1.70 log10 CFU/hand for the low-level contamination group (P < .0001). After touching an agar surface, 2.23 log10 CFU/hand was transferred in the high-contamination group compared with 0.30 log10 CFU/hand per hand in the low-level contamination group (P = .001).

The researchers also conducted a field study in an elementary school and found that contaminated bulk-soap-refillable dispensers led to a 26-fold increase in Gram-negative bacteria on the hands of students and staff (1.42 log10 CFU) per hand. The study included 12 adult staff members and 10 students in the fourth and fifth grades.

When students and staff washed their hands from dispensers with sealed refills, the researchers noted a 2-fold reduction in bacteria on hands (0.30 log10 CFU per hand). Sealed-soap refills also led to lower levels of Gram-negative bacteria transferred to surfaces after washing (0.06 log10 CFU) compared with contaminated bulk-soap-refillable containers (0.74 log10 CFU; P < .01).

Because of certain limitations in this trial, the authors suggest that future study designs include the identification of microbes present on the hands before and after washing, comparison of results between dominant and nondominant hands, and assessment of hand-washing techniques (eg, volume of soap used, length of washing and rinsing, paper towel use behaviors, etc) used by participants.

Appl Environ Microbiol. 2011;9:2898-2904. Full text