Bar soap or liquid soap?
An article in the journal “Applied and Environmental Microbiology” (a biweekly peer-reviewed scientific journal published by the American Society for Microbiology. It was established in 1953 as Applied Microbiology and obtained its current name in 1975) talks about bacterial flora in-use soap products.
The article makes a comparison has been made of the in-use bacterial load of two bar soaps with and without antibacterials and two liquid soaps in five different locations over a 1-week period. Of the 25 samples taken from each soap, 92 to 96% of samples from bar soaps were culture positive as compared to 8% of those from liquid soaps.
Bacterial populations ranged from 0 to 3.8 log CFU per sample for bar soaps and from 0 to 2.0 log CFU per sample for liquid soaps. The mean bacterial populations per sample were 1.96 and 2.47 log CFU for the two bar soaps, and 0.08 and 0.12 log CFU for the two liquid soaps. The difference in bacterial population between bar soaps and liquid soaps was statistically significant (P = 0.005).
Staphylococcus aureus was isolated on three occasions from bar soaps but not from liquid soaps. S. aureus was isolated twice from the exterior of the plastic dispensers of liquid soap but not from the soap itself. Gram-negative bacteria were cultured only from soaps containing antibacterials. Bacterial populations on bar soaps were not high compared with bacterial populations on hands, and the flora was continually changing without evidence of a carrier state.