A loophole in soap dispensers mediates contamination with Gram‐negative bacteria

Liquid soap dispensers are widely used in domestic and clinical settings. In previous studies, the risk of bacterial contamination of refillable systems was pointed out and a bacterial contamination rate of 25%, with values of up to 10(8) colony‐forming units/mL (CFU/mL), was reported. However, the route of contamination remains elusive. To address this point, we determined the microbial contamination of refillable standard pump dispensers and nonrefillable press‐dispenser systems. Following the collection of 104 liquid soap dispensers from hotel rooms across Germany, bacterial counts were determined. Isolates of samples containing nonfastidious Gram‐negative((lac−)) bacteria were further analyzed by the Vitek 2 system for the determination of species. 70.2% of the refillable pump dispensers (mean total bacterial count = 2.2 × 10(5) CFU/mL) but only 10.6% of the nonrefillable press dispensers, were contaminated (mean total bacterial count = 1.5 × 10(1) CFU/mL). Of samples containing nonfastidious Gram‐negative ((lac−)) bacteria, Pluralibacter gergoviae was present in 41.7%, Pseudomonads (Pseudomonas aeruginosa and Pseudomonas putida) in 25%, Serratia marcescens in 16.7%, and Klebsiella oxytoca and Pasteurella testudinis in 8.3%. After the initial assessment, we contaminated different dispensing systems with P. aeruginosa/P. gergoviae, to reveal the route of contamination and identied the pressure release of standard pump dispensers as the loophole for microbial contamination.