title: Clostridium difficile contamination of public tap water distribution system during a waterborne outbreak in Finland.
abstract: OBJECTIVE
  In November through December 2007, the drinking water distribution system in the town of Nokia, Finland, was contaminated with treated sewage effluent that resulted in a large gastroenteritis outbreak in the community. The aim of the present study was to investigate if the contaminated water in this outbreak was also a potential source of Clostridium difficile infections.
  
  
  METHODS
  Samples from the contaminated tap water and treated sewage effluent were collected. Stool samples from a portion of patients that fell ill during the outbreak were examined for C. difficile. PCR ribotyping was performed on toxin positive C. difficile isolates and the genetic profiles of the water and patient isolates were compared.
  
  
  RESULTS
  Twelve toxin-positive C. difficile isolates were found in water samples: five from contaminated tap water and seven from treated sewage effluent. Among these, four and five distinct PCR ribotype profiles were identified, respectively. Four PCR ribotype profiles were found among nine human faecal C. difficile isolates. Two isolates, one from tap water and one from a patient, had an indistinguishable PCR ribotype profile.
  
  
  CONCLUSIONS
  Our findings demonstrate for the first time C. difficile contamination of a tap water distribution system and waterborne transmission of toxigenic C. difficile seems possible.
authors.affiliation: National Institute for Health and Welfare (THL), Department of Infectious Disease Surveillance and Control, Bacteriology Unit/Epidemiologic Surveillance and Response Unit, Helsinki, Finland.
authors.forename: Saara M
authors.initials: SM
authors.lastname: Kotila
authors.forename: Tarja
authors.initials: T
authors.lastname: Pitkänen
authors.forename: Jon
authors.initials: J
authors.lastname: Brazier
authors.forename: Erkki
authors.initials: E
authors.lastname: Eerola
authors.forename: Jari
authors.initials: J
authors.lastname: Jalava
authors.forename: Markku
authors.initials: M
authors.lastname: Kuusi
authors.forename: Eija
authors.initials: E
authors.lastname: Könönen
authors.forename: Janne
authors.initials: J
authors.lastname: Laine
authors.forename: Ilkka T
authors.initials: IT
authors.lastname: Miettinen
authors.forename: Risto
authors.initials: R
authors.lastname: Vuento
authors.forename: Anni
authors.initials: A
authors.lastname: Virolainen
mesh_terms: D016360:Clostridioides difficile / Q000302:isolation & purification*; D003015:Clostridium Infections / Q000453:epidemiology* / Q000635:transmission; D004196:Disease Outbreaks; D005243:Feces / Q000382:microbiology; D005387:Finland / Q000453:epidemiology; D006801:Humans; D016133:Polymerase Chain Reaction; D021521:Ribotyping; D014871:Water Microbiology; D014881:Water Supply / Q000032:analysis*
keywords: Clostridium difficile infection; Clostridium difficile spores; PCR ribotyping; waterborne outbreak