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Diagnostic difficulties of Lactobacillus casei bacteraemia in immunocompetent patients: A case report

Chiara Tommasi1*, Francesco Equitani2, Marcello Masala3, Milva Ballardini3, Marco Favaro4, Marcello Meledandri3, Carla Fontana4, Pasquale Narciso1 and Emanuele Nicastri1

Author Affiliations

1 National Institute for Infectious Diseases, INMI 'L. Spallanzani', via portuense, 00149 Rome, Italy

2 S. Filippo Neri General Hospital – Department of Transfusion Medicine and Hemotherapy, via Martinotti, 00135 Rome, Italy

3 S. Filippo Neri General Hospital, via Martinotti, 00135 Rome, Italy

4 Department of Microbiology, Polyclinic of 'Tor Vergata', viale Oxford, 00133 Rome, Italy

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Journal of Medical Case Reports 2008, 2:315  doi:10.1186/1752-1947-2-315

Published: 30 September 2008



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.

Case presentation

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.


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.