Intra- and Interspecies Conjugal Transfer of Tn 916 -Like Elements from Lactococcus lactis In Vitro and In Vivo

Abstract

Tetracycline-resistant Lactococcus lactis strains originally isolated from Polish raw milk were analyzed for the ability to transfer their antibiotic resistance genes in vitro, using filter mating experiments, and in vivo, using germfree rats. Four of six analyzed L. lactis isolates were able to transfer tetracycline resistance determinants in vitro to L. lactis Bu2-60, at frequencies ranging from 10 ؊5 to 10 ؊7 transconjugants per recipient. Three of these four strains could also transfer resistance in vitro to Enterococcus faecalis JH2-2, whereas no transfer to Bacillus subtilis YBE01, Pseudomonas putida KT2442, Agrobacterium tumefaciens UBAPF2, or Escherichia coli JE2571 was observed. Rats were initially inoculated with the recipient E. faecalis strain JH2-2, and after a week, the L. lactis IBB477 and IBB487 donor strains were introduced. The first transconjugants were detected in fecal samples 3 days after introduction of the donors. A subtherapeutic concentration of tetracycline did not have any significant effect on the number of transconjugants, but transconjugants were observed earlier in animals dosed with this antibiotic. Molecular analysis of in vivo transconjugants containing the tet(M) gene showed that this gene was identical to tet(M) localized on the conjugative transposon Tn916. Primer-specific PCR confirmed that the Tn916 transposon was complete in all analyzed transconjugants and donors. This is the first study showing in vivo transfer of a Tn916-like antibiotic resistance transposon from L. lactis to E. faecalis. These data suggest that in certain cases food lactococci might be involved in the spread of antibiotic resistance genes to other lactic acid bacteria.

Identification and characterization of tetracycline resistance in Lactococcus lactis isolated from Polish raw milk and fermented artisanal products

“…The transferability of Tn916 to other bacteria was proven in our laboratory by Boguslawska et al (2009) and was confirmed by others research groups (Agerso et al, 2002;Poyart et al, 2000). Moreover, Boguslawska et al showed that the tet(S) gene can be transferred between bacteria strains, which was likely connected with the presence of the plasmid.…”

Detection of tetracycline and macrolide resistance determinants in enterococci of animal and environmental origin using multiplex PCR

“…Numerous studies have already shown that TET resistance is typically transferable and a variety of plasmids have been observed (Boguslawska et al 2009;Kazimierczak et al 2009). There are currently 38 different tet resistance genes described (Cauwerts et al 2006).…”

“…There are currently 38 different tet resistance genes described (Cauwerts et al 2006). Gene tet(M) encoding ribosomal protection and gene tet(L) determining efflux transporter have been the most often genes identified in poultry enterococci (Boguslawska et al 2009). Acquired resistance to macrolides in enterococci is often associated with the expression of erm(B) (erythromycin-ribosome-methylase) gene (Gupta et al 2009).…”

Resistance to the tetracyclines and macrolide-lincosamide-streptogramin group of antibiotics and its genetic linkage – a review

“…Transfer of antimicrobial resistance, however, is highly influenced by the complexity of microflora and its interactions with the host. Moreover, it is presumed that in vitro models underestimate the potential risk for resistance transfer compared to in vivo models [58,59]. Therefore, to appropriately assess the risk for horizontal spread of antimicrobial resistance, many authors have recently performed experimental studies under in vivo conditions.…”