Enterococcus, Salmonella y H2S: Control Remoto de la Resistencia a Antibioticos
Daniel Thomas López defended the PhD Thesis at the Faculty of Veterinary Medicine of the Complutense University of Madrid
May 29th, 2017
Enterococcus faecalis and Enterococcus faecium are among the most significant hospital pathogens globally, producing life threatening endocarditis, urinary tract infections and septicemia. This is due, among other reasons, to their high-level of resilience to adverse environmental conditions, and to their resistance to a wide range of antibiotics. Of all the antimicrobial resistance mechanisms harbored by enterococci, their intrinsic resistance to cephalosporins (an invaluable group of antibiotics within β- lactams family) is the most troubling from a clinical perspective, as it leads to a substantial reduction of the treatment options available for fighting enterococcal infections. In this Thesis, we have discovered a phenomenon that abolishes Enterococcus resistance, making them susceptible to cephalosporin activity. This sensitization occurs when enterococi are exposed to the gas hydrogen sulfide (H₂S. This gas, which has been considered a mere cell by-product for centuries, is now recognized as a highly relevant gasotransmitter, involved in various physiological and pathological processes, both in Eukaryotes and Prokaryotes. Furthermore, in our work we have revealed that, enterococci do not only become susceptible to cephalosporins when H₂S is in the media, but the same phenotype is observed when the H₂S is produced by another bacterium, even if both species arephysically separated one from the other. Thus, this Thesis constitutes a significant progress in two different fields. On the one hand, the fact that Enterococcus becomes susceptible to the combination of cephalosporins and H₂S opens the door for the development of future therapeutic alternatives against multidrug resistant pathogens. On the other hand, to the best of our knowledge, this is the first description of a bacterium remotely producing an effect with lethal consequences on another species, demonstrating, once again, the immense complexity of the microbial world.
