Overcoming Bacterial Resistance using a Macrolide-Antimicrobial Peptide Chimera – OBARMAC

Antimicrobial resistance to antibiotics is a serious threat to the human health. In this frame, the WHO identified the ESKAPE pathogens (E. faecium, S. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, and Enterobacter spp.) as critical targets for drug discovery. They are the leading cause of nosocomial infections worldwide, and most are multidrug-resistant. Macrolides are a clinically significant class of antibiotics, mostly used against Gram(+) bacteria. They inhibit protein synthesis by obstructing the peptide exit tunnel (PET) in the ribosome, but their used is challenged by the emergence of resistances. Proline-rich antimicrobial peptides (PrAMPs) are a promising new class of antibiotics that enter the bacterial cytosol using inner membrane transporters and also bind into the PET. They show strong antimicrobial activity against some of the most alarming multidrug-resistant Gram(-) species. Structures of ribosomes bound to macrolides or PrAMPs have revealed a partial overlap in their respective binding sites within the PET, a priori hindering the concurrent binding of these two antibiotic classes. However, based on robust biophysical data, we recently showed that, unexpectedly, the simultaneous interaction of a macrolide and a PrAMP in the PET was actually possible. This concomitant binding was confirmed by a cryoEM structure of a ribosome with a macrolide bound to the PET next to a PrAMP, slightly displaced from its original binding site. The aim of this project is to rationally synthesize, based on our previous biophysical and structural data, a series of macrolide-PrAMP conjugates able to bind the ribosome PET. Such compounds should overcome some macrolide resistance in Gram(+) bacteria and broaden the activity spectrum by facilitating internalization in Gram(-) bacteria. Best candidates will be selected using biophysical and microbiological assays and their interaction with the ribosome of ESKAPE species will be analyzed at the atomic level by cryoEM.