Efficacy of Antimicrobial Compounds in Soaps to Reduce E. coli and E. faecalis in a Soiled Hand-washing Model

Introduction: It has been demonstrated that contaminated hands are among the main sources for transmission of foodborne pathogens. In the agricultural environment, hands could become easily contaminated during work activities caused in many cases, by poor hygiene practices. 

Purpose: To evaluate the reduction of Escherichia coli and Enterococcus faecalis in soiled hands after washing with soaps with various antimicrobial compounds, and determine microbial survival in rinsates.

Methods: Four commercial soaps with different antimicrobial compounds were analyzed. Escherichia coli ATCC 25922 and Enterococcus faecalis ATCC 19433 were inoculated (10³ and 10⁶ CFU/g, final concentration) on sterilized agricultural soil. Previously-decontaminated hands were put in contact with soil for 2 min, and immediately washed with liquid soaps with and without antimicrobial compounds (non-antimicrobial bland soap, triclosan, citric extracts, chloroxylenol, chlorhexidine gluconate and distilled water (control). Remained bacteria on hands were determined by a membrane filtration method using selective media (Rapid E. coli 2 Agar and Streptococcus KF Agar plates). Hand rinsates were collected and incubated for 20 h at 25°C, and viable bacteria were determined at various times. Results were analyzed with NCSS, LLC Version 6.0.

Results: Washing hands with soap with chlorhexidine gluconate provided the lowest concentration of E. coli remained per hand (P<0.05) (3.17 ± 0.0 log CFU [99.9% of reduction] and 4.17 ± 0.2 log CFU [99.99% of reduction]), when inocula of 10³ and 10⁶ CFU/ml were applied, respectively. Similarly, for E. faecalis the higher reduction was obtained with chlorhexidine gluconate, [3.0 log CFU to 3.15 ± 0.3 log CFU (99.9% of reduction)] followed by chloroxylenol [6.0 log CFU to 4.43 ± 0.3 log CFU (99.99% of reduction)]. In most cases, the level of viable bacteria in rinsates remained constant during the period analyzed. 

Significance: This study shows the efficacy of antimicrobial soaps in soiled hands which can be used to reduce contamination during handling products.