title: Diagnostic difficulties of Lactobacillus casei bacteraemia in immunocompetent patients: a case report.
abstract: BACKGROUND
  Lactobacilli are currently proposed as probiotic agents in several dietary products. In blood cultures, they are usually considered as contaminants, but in recent years they have been recognized as causal infectious agents of endocarditis, urinary tract infections, meningitis, intra-abdominal infections and bacteraemia.
  
  
  METHODS
  We report a case of Lactobacillus casei bacteraemia in a 66-year-old immunocompetent man with a history of fever of unknown origin. Leuconostoc bacteraemia was demonstrated by blood culture, but a later polymerase chain reaction analysis with sequencing of 16S ribosomal RNA identified Lactobacillus casei and a successful antibiotic therapy was performed.
  
  
  CONCLUSIONS
  Bacteraemia caused by probiotic organisms is rare but underestimated, since they are normally regarded as contaminants and their role as primary invaders is not always easily established. Although the consumption of probiotic products cannot be considered a risk factor in the development of diseases caused by usually non-pathogenic bacteria, specific individual clinical histories should be taken into account. This report should alert both clinicians and microbiologists to the possibility of unusual pathogens causing serious illnesses and to the use of 16S ribosomal RNA sequencing for molecular identification as a powerful tool in confirming the diagnosis of infrequent pathogens.
authors.affiliation: National Institute for Infectious Diseases, INMI 'L, Spallanzani', via portuense, Rome, Italy. ch.tommasi@tiscali.it
authors.forename: Chiara
authors.initials: C
authors.lastname: Tommasi
authors.forename: Francesco
authors.initials: F
authors.lastname: Equitani
authors.forename: Marcello
authors.initials: M
authors.lastname: Masala
authors.forename: Milva
authors.initials: M
authors.lastname: Ballardini
authors.forename: Marco
authors.initials: M
authors.lastname: Favaro
authors.forename: Marcello
authors.initials: M
authors.lastname: Meledandri
authors.forename: Carla
authors.initials: C
authors.lastname: Fontana
authors.forename: Pasquale
authors.initials: P
authors.lastname: Narciso
authors.forename: Emanuele
authors.initials: E
authors.lastname: Nicastri