Hand soap contamination by Pseudomonas aeruginosa in a tertiary care hospital: whole genome sequencing ruled out any impact on patients. Hand soap contamination by Pseudomonas aeruginosa

During an environmental investigation of Pseudomonas aeruginosa in ICUs, the liquid hand soap was found highly contaminated (up to 8x105 cfu/g) with this pathogen. It had been used over the previous 5 months and was probably contaminated during manufacturing.Our aim was to evaluate the burden of this contamination on patients by conducting an epidemiological investigation using molecular typing combined with whole genome sequencing (WGS).P. aeruginosa isolates from clinical specimens were analysed by double locus sequence typing (DLST) and compared to isolates recovered from the soap. Medical charts of patients infected with a genotype identical to those found in the soap were reviewed. WGS was performed on soap and patient isolates sharing the same genotype.P. aeruginosa isolates (N=776) were available in 358/382 patients (93.7%). Only 3 patients (0.8%) were infected with a genotype found in the soap. Epidemiological investigations showed that the first patient was not exposed to the soap, the second could have been exposed, and the third was indeed exposed. WGS showed a high number of core SNPs differences between patients and soap isolates. No close genetic relation was observed between soap and patient isolates, ruling out the hypothesis of transmission.Despite a highly contaminated soap, the combined investigation with DLST & WGS ruled out any impact on patients. Hand hygiene carried out with alcoholic solution for over 15 years was probably the main reason. However, such contamination represents a putative reservoir of pathogens which should be avoided in the hospital setting.