Atividade antimicrobiana do extrato de Vismia guianensis contra Escherichia coli in vitro e in vivo

Abstract

Vismia guianensis (Aubl.) Choisy, from the Hypericaceae family and popularly known as "lacre," has been the focus of bioprospecting studies due to its antioxidant, antimicrobial, and anti-inflammatory properties. This study investigated the antibacterial activity of Vismia guianensis leaf extract (EHVG) against Escherichia coli both in vitro and in vivo. The in vitro evaluation determined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against a standard strain of Escherichia coli (ATCC 25923), a clinical isolate (E. coli 31218), and an enteropathogenic strain (EPEC 2348/69). Additionally, the impact of EHVG on virulence factors, including adhesion and biofilm formation, was assessed. In vivo experiments used T. molitor larvae to standardize the lethal inoculum, exposing them to E. coli concentrations ranging from 10110^1 to 10910^9 CFU/mL. To investigate the effects of EHVG on lethally infected larvae, the larvae were divided into six groups (n=10 per group): Sham – without infection or treatment, and five infected groups treated via intracelomic injection (ic – 10 µL) as follows: Control – received PBS; MERO – treated with Meropenem (0.625 µg/mL); EHVG½ – treated with half the MIC value (62.5 µg/mL); EHVG – treated with the MIC concentration (125 µg/mL), and EHVG2 – treated with twice the MIC concentration (250 µg/mL). The standard strain E. coli ATCC 25922 showed the highest sensitivity to EHVG (MIC of 125 µg/mL), while other strains exhibited MIC values ranging from 500 µg/mL (EPEC 2348/69) to 1000 µg/mL (E. coli 31218). MBC values were consistent across all tested strains (1000 µg/mL), and the MBC/MIC ratio indicated bactericidal activity. EHVG effectively reduced biomass and viability, impacting adhesion, preformed biofilms, and formed biofilms. In vivo, EHVG treatment prolonged the survival of T. molitor larvae lethally infected with E. coli, with the most significant effect observed at the highest dose (EHVG2). In conclusion, EHVG enhances the survival of lethally infected larvae due to its bactericidal properties and the inhibitory effects on virulence factors in various E. coli strains.