- Spatial organization and Horizontal gene transfer of Antibiotic Resistance by ESBL in WasteWater

This innovative project intends to address the current knowledge gaps concerning the biofilm spatial organization and interspecies interactions that underlie the antibiotic resistance strategy by extended spectrum β-lactamase (ESBL) producing bacteria.

Background and aim
The tidal increase of clinical antibiotic resistance is of serious threat to public health and should be viewed as an integrated system influenced by the environmental dimension of antibiotic resistance (ABR). The European Union (EU) has declared that antimicrobial resistance annually costs EUR 1.5 billion in healthcare costs and productivity losses. By 2050, drug-resistant infections could cause global economic damage on a par with the 2008 financial crisis. This project, with extreme importance in both health and economic framework, is particularly timely due to the current situation of antibiotic resistance (ABR), already responsible for an estimated 25,000 deaths per year in the EU, and that compromise the success of major surgeries, cancer chemotherapy and the fight against other microorganisms.

This project has three main objectives: 1) Evaluate the impact of ESBL gene sharing by conjugation in the biofilm collective ABR and its interdependence with bacterial spatial organization; 2) Evaluate the biofilm β-lactam resistance strategy at a functional level by following the expression and localization of ESBL and other ABR related proteins; 3) Evaluate the potential of wastewater treatment plants as hotspots for ABR by assessing the sharing of ESBL genes and their expression. Antimicrobial resistance has been declared as an important global economic and a societal challenge, that must be tackled by a multi-sectorial approach, where the environmental sector is included.

We are only at the tip of the iceberg of how spatial organization and interspecies interactions affect each other; even more if we focus on the effect of ESBL gene sharing by conjugation in wastewater bacteria biofilms, a theme underexplored, but incredibly relevant to understand the proliferation and dissemination of ABR by WWTPs. In WWTP bacteria are present in high biomass concentrations, with high probability of cell-to-cell contact, while being continuously exposed to the selective pressure of sub-inhibitory antibiotic concentrations, an environment well suited for horizontal gene transfer (HGT) to occur by conjugation. The worldwide spread ESBL gene bla CTX-M is carried by plasmids. These genes are among the ABR determinants to which wastewater conventional treatments are inefficient in eliminating, consequently being disseminated into the environment. Because conjugation only occurs between the closest neighbours and enzymes have a low diffusion coefficient in the biofilm matrix, ESBL gene sharing is expected to have an impact on the spatial organization of the different species. However, this impact is not yet described, and would reveal part of the molecular basis of β-lactam collective ABR strategy by wastewater bacteria.
This project will make important advances in the field of β-lactam ABR proliferation and environmental spread, and the results will have great relevance for research and practitioners from other sectors like public health, clinical practice and biotechnology.