title: Hand soap contamination by Pseudomonas aeruginosa in a tertiary care hospital: no evidence of impact on patients.
abstract: BACKGROUND
  During an environmental investigation of Pseudomonas aeruginosa in intensive care units, the liquid hand soap was found to be highly contaminated (up to 8 × 10(5)cfu/g) with this pathogen. It had been used over the previous five months and was probably contaminated during manufacturing.
  
  
  OBJECTIVE
  To evaluate the burden of this contamination on patients by conducting an epidemiological investigation using molecular typing combined with whole genome sequencing (WGS).
  
  
  METHODS
  P. aeruginosa isolates from clinical specimens were analysed by double locus sequence typing (DLST) and compared with 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.
  
  
  RESULTS
  P. aeruginosa isolates (N = 776) were available in 358/382 patients (93.7%). Only three 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 single nucleotide polymorphism differences between patients and soap isolates. No close genetic association was observed between soap and patient isolates, ruling out the hypothesis of transmission.
  
  
  CONCLUSIONS
  Despite a highly contaminated soap, the combined investigation with DLST and WGS ruled out any impact on patients. Hand hygiene performed with alcohol-based solution for >15 years was probably the main reason. However, such contamination represents a putative reservoir of pathogens that should be avoided in the hospital setting.
authors.affiliation: Service of Hospital Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland; Nurse Directorate, Lausanne University Hospital, Lausanne, Switzerland. Electronic address: Dominique.Blanc@chuv.ch.
authors.forename: D S
authors.initials: DS
authors.lastname: Blanc
authors.affiliation: Service of Hospital Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Gomes Magalhaes
authors.affiliation: Service of Hospital Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Abdelbary
authors.affiliation: Institute of Microbiology, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Prod'hom
authors.affiliation: Institute of Microbiology, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Greub
authors.affiliation: Medical Directorate, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: J B
authors.initials: JB
authors.lastname: Wasserfallen
authors.affiliation: Nurse Directorate, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Genoud
authors.affiliation: Service of Hospital Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Zanetti
authors.affiliation: Service of Hospital Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Senn
mesh_terms: D004783:Environmental Microbiology; D016680:Genome, Bacterial; D005838:Genotype; D006801:Humans; D058889:Molecular Typing; D011552:Pseudomonas Infections / Q000453:epidemiology* / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D017422:Sequence Analysis, DNA; D012915:Soaps; D062606:Tertiary Care Centers
chemical_list: D012915:Soaps
keywords: Contamination; Epidemiological investigation; Intensive care unit; Molecular typing; Pseudomonas aeruginosa; Soap; Whole genome sequencing