Beyond antiparasitic activity: elucidating the antibacterial potency of pyrvinium pamoate Alcaraz Martínez, Ángela Muñoz-Báez, Paloma Peñalver, Pablo Morales Vega, Juan Carlos Cebrián, Rubén pyrvinium pamoate Antimicrobial resistance Drug repurposing Antimicrobial resistance represents a critical global health threat, demanding innovative therapeutic strategies. In this study, we investigate the repurposing potential of pyrvinium pamoate (PP)—a long-established anthelmintic agent—for antibacterial applications. Comprehensive in vitro analyses revealed that while gram-negative bacteria exhibited inherent resistance due to limited drug uptake, gram-positive pathogens, particularly within the orders Actinomycetales and Bacillales, were markedly susceptible at low micromolar concentrations. Enhanced antibacterial efficacy was observed when PP was combined with outer membrane-permeabilizing agents, such as the peptide D11 or pentamidine, which facilitated increased intracellular accumulation. Additionally, the role of efflux pump activity was explored; its inhibition in Staphylococcus aureus resulted in significant drug retention and a concomitant reduction in minimum inhibitory concentrations, while disruption of the proton motive force attenuated uptake. The compound demonstrated bactericidal effects against S. aureus and a bacteriostatic profile against Pseudomonas aeruginosa when sensitized with outer membrane permeabilizing agents. Furthermore, synergistic studies with several antibiotics revealed the potential of PP as a valuable addition to the antimicrobial arsenal against multidrug-resistant pathogens. These findings motivate further mechanistic studies and clinical evaluation of PP in antimicrobial therapy. PP shows promise as a repurposed antibacterial agent, particularly against gram-positive pathogens, with enhanced activity against gram-negative pathogens when combined with membranepermeabilizing agents or in the presence of efflux pump inhibitors. 2025-10-10T10:59:03Z 2025-10-10T10:59:03Z 2025-09-30 journal article Alcaraz-Martínez A, Muñoz-Báez P, Peñalver P, Morales JC, Cebrián R.0.Beyond antiparasitic activity: elucidating the antibacterial potency of pyrvinium pamoate. Microbiol Spectr0:e02158-25.https://doi.org/10.1128/spectrum.02158-25 https://hdl.handle.net/10481/106953 10.1128/spectrum.02158-25 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional American Society for Microbiology