Prospecção do Extrato Fresco e Frações de Pariri (Fridericia chica) frente a Aeromonas Patogênicas Multirresistentes a Antimicrobianos Isoladas de Tambaquis (Colossoma macropomum) da Ilha do Maranhão

Abstract

The presence of multidrug-resistant bacteria in aquatic environments represents a challenge to fish health and public health. Given the scarcity of antimicrobials regulated for use in native fish, interest in natural alternatives, such as plant extracts, has increased. Thus, this study aimed to prospect the fresh extract and fractions of pariri (Fridericia chica (Bonpl.) L.G. Lohmann) against pathogenic Aeromonas spp. multidrug-resistant to antimicrobials isolated from tambaqui originating from the Island of Maranhão. For this purpose, 54 bacterial isolates from C. macropomum were used, confirmed as belonging to the genus Aeromonas sp. by phenotypic and molecular tests and characterized as multidrug-resistant to commercially used antibiotics. For the evaluation of the antimicrobial profile, the fresh leaf extract of F. chica and its fractions (hexane, dichloromethane, ethyl acetate, and aqueous) were prepared through maceration, rotary evaporation, lyophilization, and liquid–liquid partitioning processes. The determination of total phenolic compounds and flavonoids in the extract and fractions was performed using the Folin–Ciocalteu method and linear regression, with readings taken using a spectrophotometer, while mass spectra of the fresh extract were determined by direct infusion into a mass spectrometer. The antimicrobial activity of the isolates was evaluated using the fresh extract and fractions, with the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) determined. For MIC determination, resazurin was used as a viability marker by the microdilution method in microplates, and for MBC determination, the spread-plate method with plate count agar was applied. Toxicity assessment was carried out through an in vivo test of the extract and its fractions using 120 larvae of the species Tenebrio molitor. Gentamicin was used as a positive control in both MIC and MBC assays. The fresh extract (3172 ± 1.90) and the ethyl acetate fraction (2605 ± 1.65) exhibited the highest levels of total phenolics and total flavonoids. Chemical analysis of the fresh extract identified the compounds carajurone (m/z 285.0723) and carajurin (m/z 299.0876). In MIC assays, the ethyl acetate fraction (1.95 µg/mL) and the dichloromethane fraction (15.62–31.25 µg/mL) showed the best performance in inhibiting the growth of the 54 isolates, followed by the fresh extract (39.06–10,000 µg/mL). In contrast, the hexane and aqueous fractions (10,000 µg/mL) were weak inhibitors. Gentamicin exhibited similar antimicrobial activity in both MIC and MBC assays, ranging from 3.12 to 25 µg/mL. Extracts of F. chica showed low acute toxicity in T. molitor, with 100% survival in the controls and a slight reduction in survival rate only at the highest concentration tested for the dichloromethane fraction. It is concluded that the ethyl acetate and dichloromethane fractions of F. chica demonstrated potent to moderate activity against Aeromonas spp. isolates obtained from C. macropomum. The results of this study highlight the potential of F. chica in the control of aeromonosis in tambaqui, contributing to the reduction of synthetic antibiotic use and strengthening actions aimed at biodiversity conservation and ecosystem protection against the spread of antimicrobial resistance. As a way to promote discussion on antimicrobial resistance in aquatic organisms and its direct impact on the One Health approach, an educational guide (illustrated and written in accessible language) was developed, reinforcing the mission of universities to produce and disseminate knowledge both within and beyond academic environments, fostering dialogical interaction, interdisciplinarity, the inseparability of teaching–research–extension, and positive impacts on student education and social transformation.