This double-blind study determined whether consumption of a Lactobacillus reuteri strain harbouring a plasmid containing the tetracycline resistance gene resulted in a detectable tetracycline resistance signal in faecal bacteria including enterococci, bifidobacteria and lactobacilli.
Subjects consumed either an Lactobacillus reuteri strain harbouring the tetracycline resistance gene (ATCC 55730) (n=7) or a control strain (n=7) from which the plasmid had been removed (DSM 17938).
For both arms of the study the Lactobacillus reuteri dose was 5 x 10^8 CFU/day for 14 days. Both strains were detectable at similar levels in the faeces but no tetracycline resistance signal was detected in any of the bacterial DNA samples collected.
Conclusion: Gene transfer during intestinal passage of the probiotic strain Lactobacillus reuteri ATCC 55730 was non-detectable under the conditions tested.