Worst-case scenarios for horizontal gene transfer from Lactococcus lactis carrying heterologous genes toEnterococcus faecalisin the digestive tract of gnotobiotic mice

Vancomycin-Resistant Lactococcus lactis 1A-1 Isolated from a Competitive Exclusion Product Transfers Vancomycin Resistance Genes to Staphylococcus aureus

“…Horizontal gene transfer rates of mobilizable plasmids from L. lactis to E. faecalis have been measured in the digestive tracts of gnotobiotic mice at 3-4 log 10 CFU/g feces [27]. Evidence also exists for the ability of lactococci to transfer genes to Enterobacteriaceae [28], so it is unclear how widely L. lactiscontaminated poultry meat could spread vancomycin resistance genes in the GI tracts of human consumers.…”

A Probiotic <i>Lactobacillus</i> Strain Can Acquire Vancomycin Resistance during Digestive Transit in Mice

“…When inoculated to germ-free mice, both donor strains established and stabilized in less than 48 h at nearly 10 10 colony-forming units (CFU)/g of feces, as previously described for different Enterococcus species in the digestive tract of monoxenic mice [Alpert et al, 2003;Gruzza et al, 1993;Moubareck et al, 2003]. Once introduced into the digestive tract of mice harboring HC or TU donors, the population of recipient cells increased during the first days and reached similar levels as the donors after 72 h. Both donor and recipient populations then remained stable throughout the experiment at similar levels.…”

“…In vitro conjugations were carried out by the filtermating technique previously described [Alpert et al, 2003;Mater et al, 1999]. BHI agar plates containing 10 g/ml vancomycin, MRS agar plates containing 25 g/ ml fusidic acid, or MRS agar plates containing both antibiotics were used for selection and enumeration of donor, recipient and transconjugant clones, respectively.…”

“…C3H/He mice maintained in isolators as previously described [Alpert et al, 2003] were used to address the question whether transfer of vancomycin resistance can occur in the digestive tract. To obtain gnotoxenic mice colonized with the donor strain, 5 germ-free mice were orogastrically inoculated with 250 l of a 10-fold diluted fresh overnight culture of the donor strain.…”

Live genetically modified bacteria as drug delivery tools: at the doorstep of a new pharmacology?

“…This has been addressed by exchanging thyA, the gene encoding the essential enzyme thymidylate synthase, for hil-10 [18]. This firmly embeds the genetic modification in the chromosome, which prevents lateral dissemination to a very large extent [19]. The resulting strain, L. lactis Thy12, becomes critically dependent on the addition of thymidine or thymine to the growth medium.…”