Purpose: To address this assumption, the goal of this project was to determine if, on farmworker hands, visible “soil” on farmworker hands was associated with microbial load.
Methods: A total of 181 farmworkers were asked to wash their hands to standardize hand microbial loads. Workers were then asked to harvest tomatoes without gloves for 30 minutes, practice hand hygiene (e.g., hand wash, hand sanitizers) and then rinse their hands in 0.1% peptone solution. The solutions were analyzed for Absorbance600nm (turbidity) and microbial load (Enterococcus spp., coliforms and E. coli). Hands were photographed after rinsing and assigned a “Hand Score” based on visible soil on the palm, soil on the finger pads, soil under the fingernails, multicolored soil, and total soil by two independent reviewers.
Results: Hands ranged in Absorbance600nm (0.175 ± 0.19 SD), Hand Score (3.9 ± 1.8 SD), log E. coli CFU/hand (1.40 ± 0.73 SD), log Enterococcus (3.84 ± 1.58 SD), and log coliforms (2.61 ± 1.59 SD). Using Spearman’s correlation tests, Absorbance and Hand Score were significantly correlated (rho=0.540, P<0.001). In contrast, Hand Score and concentrations of E. coli (rho=0.025, P=0.826) and coliforms (rho=-0.089, P=0.440) were not significantly correlated. Hand Score and concentrations of Enterococcus (rho=0.273, P=0.015) were significantly weakly correlated.
Significance: Our results suggest that while visible hand “soil” is a good proxy for hand rinse turbidity, visible “soil” is not an indicator of microbial load for all microorganisms on farmworker hands. Thus, farmworkers or managers cannot depend on visual “cleanliness” alone to assess their hands’ microbiological “cleanliness;” performing a quality hand hygiene intervention is recommended.