Effect of tetracycline on transfer and establishment of the tetracycline-inducible conjugative transposon Tn916 in the guts of gnotobiotic rats.
We have investigated the transfer of Tn916 among strains of Enterococcus faecalis OG1 colonizing in the intestines of gnotobiotic rats. This animal model allows a low limit of detection and efficient colonization of the chosen bacteria. The animals continuously received tetracycline in drinking water. A tetracycline-sensitive recipient strain was allowed to colonize the animals before the resistant donor was introduced. The numbers of donors, recipients, and transconjugants in fecal samples and intestinal segments were estimated. The bioavailable amounts of tetracycline in fecal samples and intestinal segments were monitored by using bacterial biosensors carrying a transcriptional fusion of a tetracycline-regulated promoter and a lacZ reporter gene. Chromosomal locations of Tn916 in transconjugants isolated either from the same animal or from different animals were compared by Southern blot analysis. Our results indicated that selection for the resistant phenotype was the major factor causing higher numbers of transconjugants in the presence of tetracycline. Tetracycline-sensitive E. faecalis cells colonized the intestine even when the concentrations of tetracycline in feces and intestinal luminal contents exceeded growth-inhibitory concentrations. This suggests the existence of tetracycline-depleted microhabitats in the intestinal environment.
Bahl
Martin Iain
MI
Department of General Microbiology, University of Copenhagen, 1307 Copenhagen K, Denmark.
Sørensen
Søren J
SJ
Hansen
Lars Hestbjerg
LH
Licht
Tine Rask
TR
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003227:Conjugation, Genetic; D004251:DNA Transposable Elements / Q000235:genetics*; D013293:Enterococcus faecalis / Q000235:genetics; D005260:Female; D022761:Gene Transfer, Horizontal / Q000187:drug effects*; D005856:Germ-Free Life; D007422:Intestines / Q000382:microbiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013752:Tetracycline / Q000494:pharmacology*; D013753:Tetracycline Resistance / Q000235:genetics
D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D013752:Tetracycline