Recombination of integron cassettes: in vivo and in vitro dynamics – DynamINT

Integrons are able to recruit antibiotic resistance gene cassettes via an integrase.The integrase activity will be followed in in vivo models (biofilm and murine) by an original approach of fluorescence measurement by flow cytometry.Classical techniques of genetic and molecular biology will be also performed.

Our preliminary results showed that under the bacterial lifestyle in the environment, the biofilm, the activity of the integron Integrase is more induced.These observations suggest that in the environment, the exchange and recruitment of antibiotic resistance gene cassettes may be more important than anticipated.

The knowledge of the regulation of integron Integrase in vivo, the role of antibiotics on this regulation and the details of its mechanism of action should allow to identify new therapeutic targets/pathways adjuvants to antibiotics treatments in order to prevent antibiotic resistance spread among bacteria.

No scientifif product because the project started in january 2013 with a first phase of technicals development.

The continuous emergence of multi-resistant bacteria highlights the urgent need for new therapeutic options. Resistance integrons have been identified among the major players in multi-resistance in bacteria. Integrons constitute a strikingly efficient genetic platform allowing bacterial adaptation to various bacterial stresses (including antibiotics), through the integration and excision activities of the integron integrase, IntI. The integron recombination machinery is highly advanced and specific, with the involvement of recombination and replication. The integrase expression has been shown to be regulated by the SOS response in planktonic cultures, i.e. in laboratory conditions. To better evaluate the implication of the SOS response and antibiotics effects on integrase regulation, and thus cassettes acquisition in natural conditions where horizontal gene transfers and resistance spreading are observed, we need to develop experimental models, which are closer to natural environments. The chosen models we propose to develop are biofilms and models of mouse gastrointestinal tract colonization. These two models allow establishing high concentrations of bacteria where DNA transfer and resistance exchange are predicted to occur. Besides improving our knowledge of conditions/regulation of integrase expression, we also need to characterize more finely the integrase mode of action, especially the host factors involvement, in order to find ways to interfere with the recombination steps and reduce resistance gene acquisition.
The dynamINT project, through (i) the biofilm and in vivo models approaches aimed at understanding the impact SOS response and antibiotics on the integron system and acquisition of antibiotic resistance, and (ii) the resolution of the mechanism of the precise recombination complex, should help to identify new ways to fight resistance transfer by targeting either the inducing signal pathway like the SOS response, or the actor of resistance gene acquisition/exchange, the integron integrase.