Importance of Molecular Methods to Determine Whether a Probiotic is the Source of Lactobacillus Bacteremia

Abstract

There has been an increasing interest in the use of probiotic products for the prevention of Clostridium difficile infection (CDI). Bio-K+(®) is a commercial probiotic product comprising three strains of lactobacilli--Lactobacillus acidophilus CL1285(®), Lact. casei LBC80R(®) and Lact. rhamnosus CLR2(®)--that have been applied to prevent CDI. Generally considered as safe, lactobacilli have potential to cause bacteremia, endocarditis and other infections. The source of Lactobacillus bacteremia can be normal human flora or lactobacilli-containing probiotic. The aim of this study was to assess whether probiotic lactobacilli caused bacteremia and to show the value of molecular identification and typing techniques to determine probiotic and patient strain relatedness. We report an episode of Lactobacillus bacteremia in a 69-year-old man admitted to a hospital with severe congestive heart failure. During his hospitalization, he required long-term antibiotic therapy. Additionally, the patient received Bio-K+(®) probiotic as part of a quality improvement project to prevent CDI. Subsequently, Lactobacillus bacteremia occurred. Two independent blinded laboratory evaluations, using pulse field gel electrophoresis, 16S rRNA gene sequencing and DNA fingerprint analysis (rep-PCR), were performed to determine whether the recovered Lact. acidophilus originated from the probiotic product. Ultimately, the patient strain was identified as Lact. casei and both laboratories found no genetic relation between the patient's strain and any of the probiotic lactobacilli. This clinical case of lactobacillus bacteremia in the setting of probiotic exposure demonstrates the value of using discriminatory molecular methods to clearly determine whether there were a link between the patient's isolate and the probiotic strains.

Keywords: Bacteremia; Lactobacilli; Molecular identification; Probiotic.