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The Cardiff Tracking Study

Use of colony-based bacterial strain typing for tracking the fate of Lactobacillus strains during human consumption


This study evaluated if the colony fingerprint technique (RAPD) could be used to track probiotics Lactobacillus acidophilus CUL21 (from Lab4) and Lactobacillus salivarius CUL61 (from Lab4b) during consumption by healthy volunteers.


  • The study was carried out at the School of Biosciences at Cardiff University.
  • 12 healthy volunteers were given one capsule of Lactobacillus salivarius CUL61 (18 billion cfu per capsule) and Lactobacillus acidophilus CUL21 (5.6 billion cfu per capsule) once a day for 14 days.
  • Faecal samples were collected before, during and after probiotic consumption.
  • Lactic Acid Bacteria (LAB) isolates from the participants’ stool samples were genetically typed using a Random Amplified Polymorphic DNA (RAPD) typing technique.
  • The faecal samples were then studied to identify if the LAB isolates L. salivarius CUL61 and L. acidophilus CUL21 were present before, during and after the probiotic capsule consumption.
  • RAPD fingerprinting of the major colony types appearing after cultivation of each faecal sample was used to determine if the Lactobacillus strains had survived gastric and intestinal passage.

The results

Detection of Lactobacillus salivarius CUL61 and Lactobacillus acidophilus CUL21 in faecal samples of a healthy volunteer on day 7:

Image (A) shows L. salivarius CUL61 colonies from faecal sample grown on plate. The colonies are labelled as No. 6 and No. 7

Image (B) shows L. acidophilus CUL21 colonies from faecal sample grown on plate. These colonies are labelled as Nos. 3, 4 and 5

Image (C) shows the RAPD fingerprint technique results, as follows:

Lanes 6, 7 – the fingerprint of the L. salivarius CUL61 from colonies in the faecal samples are the same as the original L. salivarius CUL61 control  (Lane 1)

Lanes 3, 4, 5 – the fingerprint of the L. acidophilus CUL21 from colonies in the faecal samples are the same as the original L. acidophilus CUL21 control (Lane 2)

Lane numbers correspond to the number labels for the colonies in the faecal samples. M is the marker column that checks that the reactions work. Lane 1 is the fingerprint for the original control for L. salivarius. Lane 2 is the control for L. acidophilus. Lanes 1 and 2 are the fingerprint of the bacterial DNA for the original pure cultures from which the probiotic strains for the capsules are produced.


Probiotic strains Lactobacillus acidophilus CUL21 (from Lab4) and Lactobacillus salivarius CUL61 (from Lab4b) remained viable and can be ‘tracked’ through the gut passage during probiotic consumption by healthy volunteers.


Mahenthiralingam E et al 2009.
Use of colony-based bacterial strain typing for tracking the fate of Lactobacillus strains during human consumption.
BMC Microbiology 2009, 9:251
(doi 10.1186/1471-2180-9-251)

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