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Applied and Environmental Microbiology, June 2000, p. 2578-2588, Vol. 66, No. 6
Department of Microbiology, University of
Otago, Dunedin,1 and New Zealand Dairy
Research Institute, Palmerston North,3 New
Zealand, and Department of Medical Microbiology, University
of Groningen, Groningen, The Netherlands2
Received 12 November 1999/Accepted 8 March 2000
The composition of the fecal microflora of 10 healthy subjects was
monitored before (6-month control period), during (6-month test
period), and after (3-month posttest period) the administration of a
milk product containing Lactobacillus rhamnosus DR20 (daily dose, 1.6 × 109 lactobacilli). Monthly fecal samples
were examined by a variety of methods, including bacteriological
culture analysis, fluorescent in situ hybridization with group-specific
DNA probes, denaturing gradient gel electrophoresis of the V2-V3 region
of 16S rRNA genes amplified by PCR, gas-liquid chromatography, and
bacterial enzyme activity analysis. The composition of the
Lactobacillus population of each subject was analyzed by
pulsed-field gel electrophoresis of bacterial DNA digests in order to
differentiate between DR20 and other strains present in the samples.
Representative isolates of lactobacilli were identified to the species
level by sequencing the V2-V3 region of their 16S rRNA genes and
comparing the sequences obtained (BLAST search) to sequences in the
GenBank database. DR20 was detected in the feces of all of the subjects
during the test period, but at different frequencies. The presence of
DR20 among the numerically predominant strains was related to the
presence or absence of a stable indigenous population of lactobacilli
during the control period. Strain DR20 did not persist at levels of
>102 cells per g in the feces of most of the subjects
after consumption of the product ceased; the only exception was one
subject in which this strain was detected for 2 months during the
posttest period. We concluded that consumption of the DR20-containing
milk product transiently altered the Lactobacillus and
enterococcal contents of the feces of the majority of consumers without
markedly affecting biochemical or other bacteriological factors.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Analysis of the Fecal Microflora of Human Subjects Consuming a
Probiotic Product Containing Lactobacillus rhamnosus
DR20
*
Corresponding author. Mailing address: Department of
Microbiology, University of Otago, P.O. Box 56, Dunedin, New
Zealand. Phone: 64-3-479-7713. Fax: 64-3-479-8540. E-mail:
gerald.tannock{at}stonebow.otago.ac.nz.
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