Microbiological evaluation of the efficacy of soapy water to clean hands: A randomized, non-inferiority field trial

We conducted a randomized, non-inferiority field trial in urban Dhaka, Bangladesh among mothers to compare microbial efficacy of soapy water (30 g powdered detergent in 1. 5 L water) with bar soap and water alone. Fieldworkers collected hand rinse samples before and after the following washing regimens: scrubbing with soapy water for 15 and 30 seconds; scrubbing with bar soap for 15 and 30 seconds; and scrubbing with water alone for 15 seconds. Soapy water and bar soap removed thermotolerant coliforms similarly after washing for 15 seconds (mean log10 reduction = 0. 7 colony-forming units [CFU], P < 0. 001 for soapy water; mean log10 reduction = 0. 6 CFU, P = 0. 001 for bar soap). Increasing scrubbing time to 30 seconds did not improve removal (P > 0. 05). Scrubbing hands with water alone also reduced thermotolerant coliforms (mean log10 reduction = 0. 3 CFU, P = 0. 046) but was less efficacious than scrubbing hands with soapy water. Soapy water is an inexpensive and microbiologically effective cleansing agent to improve handwashing among households with vulnerable children.