passages: PMC-3266646-sec-09__text
passages: sec
passages: Origins of Acquired Antibiotic Resistance Mechanisms
  Recently, D'Costa et al. (2011) have reported a metagenomic analysis of the Beringian permafrost, which is 30,000 years old. They showed molecular evidences of the ancient origins of antibiotic resistances, detecting beta-lactamases genes, vanX-like, component of the vancomycin resistance operon, and tetM, coding for a protein protecting the ribosomal target from tetracycline. Sequence analysis revealed that the beta-lactamases genes recovered from the permafrost demonstrated an amino-acid homology (53-84%) to known beta-lactamases from beta-lactams producing Streptomyces. The tetM sequences revealed a high similarity to the genes coding for the ribosomal protection protein of actinomycetes. The vanX sequence showed a similarity to the vanX gene recovered in pathogenic vancomycin resistant enterococci (VRE) and to the vanX gene from Amycolatopsis orientalis. This environmental species, belonging to the actinobacteria phylum, is a natural producer of vancomycin, and very likely the progenitor of the van genes operons, responsible for resistance to vancomycin. The integration of the van operons on transposons and on conjugative plasmids has enhanced their spread (Courvalin, 2006). Reports of VRE in freshwater have been provided by several authors (Talebi et al., 2008; Lata et al., 2009; Luczkiewicz et al., 2010). Interestingly, Schwartz et al. (2003) detected vanA genes in the biofilm of drinking water supplies, in the absence of enterococci, demonstrating the lateral transfer of this gene. Notably, the progenitors of these resistance genes are soil bacteria thus most likely, a shuttle has been responsible for the introduction of these genes into the commensal bacterial community and afterward into the pathogenic species.
  
  