title: The abundant free-living amoeba, Acanthamoeba polyphaga, increases the survival of Campylobacter jejuni in milk and orange juice.
abstract: BACKGROUND
  Campylobacter jejuni is a common cause of human bacterial diarrhea in most parts of the world. Most C. jejuni infections are acquired from contaminated poultry, milk, and water. Due to health care costs and human suffering, it is important to identify all possible sources of infection. Unpasteurized milk has been associated with several outbreaks of C. jejuni infection. Campylobacter has been identified on fresh fruit, and other gastrointestinal pathogens such as Salmonella, E. coli O157:H7 and Cryptosporidium have been involved in fruit juice outbreaks. C. jejuni is sensitive to the acidic environment of fruit juice, but co-cultures with the amoeba, Acanthamoeba polyphaga, have previously been shown to protect C. jejuni at low pH.
  
  
  METHODS
  To study the influence of A. polyphaga on the survival of C. jejuni in milk and juice, the bacteria were incubated in the two products at room temperature and at 4°C with the following treatments: A) C. jejuni preincubated with A. polyphaga before the addition of product, B) C. jejuni mixed with A. polyphaga after the addition of product, and C) C. jejuni in product without A. polyphaga. Bacterial survival was assessed by colony counts on blood agar plates.
  
  
  RESULTS
  Co-culture with A. polyphaga prolonged the C. jejuni survival both in milk and juice. The effect of co-culture was most pronounced in juice stored at room temperature. On the other hand, A. polyphaga did not have any effect on C. jejuni survival during pasteurization of milk or orange juice, indicating that this is a good method for eliminating C. jejuni in these products.
  
  
  CONCLUSIONS
  Amoebae-associated C. jejuni in milk and juice might cause C. jejuni infections.
authors.affiliation: Section of Infectious Diseases, Department of Medical Sciences, Uppsala University, Uppsala, Sweden; jenny.olofsson@lnu.se.
authors.forename: Jenny
authors.initials: J
authors.lastname: Olofsson
authors.affiliation: Section for Zoonotic Ecology and Epidemiology, Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.
authors.forename: Petra Griekspoor
authors.initials: PG
authors.lastname: Berglund
authors.affiliation: Section of Infectious Diseases, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.|Zoonosis Science Center, IMBIM, Uppsala University, Uppsala, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Olsen
authors.affiliation: Section of Infectious Diseases, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.|Zoonosis Science Center, IMBIM, Uppsala University, Uppsala, Sweden.
authors.forename: Patrik
authors.initials: P
authors.lastname: Ellström
authors.affiliation: Section for Zoonotic Ecology and Epidemiology, Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.|Department of Medicine and Optometry, eHealth Institute, Linnaeus University, Kalmar, Sweden.
authors.forename: Diana
authors.initials: D
authors.lastname: Axelsson-Olsson
keywords: C. jejuni infection; Campylobacter survival; co-culture; fruit juice; gastrointestinal pathogens; unpasteurized milk