Conjugal Transfer of Genetic Information in Gnotobiotic Mice
Dissemination of antibiotic resistance determinants has greatly increased over the past two decades, and its spread is undoubtedly a response to the increasing use of antimicrobial agents. Antibiotic resistance genes therefore constitute a suitable system to study the extent of horizontal gene transfer among prokaryotes. In a attempt to elucidate the mechanism of in vivo dissemination of genetic information between phylogenetically remote organisms, we have studied the transfer of two different genetic elements in an animal model. Since the intestinal ecosystem is the most probable meeting point for the bacterial species studied in nature, donors and recipients were associated for 35 or 40 days in the digestive tract of gnotobiotic mice. The transfer was conducted in groups of 6 adult germ-free C3H mice (Centre de selection des animaux de laboratoire, Orléans, France). The mice were maintained in Trexler- type isolators. Animals were fed at libitum with a commercial diet sterilized by gamma irradiation. They were supplied with autoclaved drinking water acidified to pH 3 to prevent any bacterial growth in the beverage. After 12 hours without water, germ-free mice were inoculated intragastrically with 1 ml of a broth culture containing 108 colony forming units (CFU) of the recipient strain.
KeywordsListeria Monocytogenes Enterococcus Faecalis Conjugal Transfer Kanamycin Resistance Gene Transfer Frequency
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