Antimicrobial resistance (AMR) represents a major global health challenge, driving the search for novel antimicrobial compounds from natural sources. Filamentous fungi are prolific producers of bioactive metabolites, yet the biological potential of fungal guttation droplets remains relatively underexplored. In this study, guttation droplets produced by Penicillium pimiteouiense and Penicillium menonorum, isolated from rhizospheric soils of Opuntia spp. in Colima, Mexico, were evaluated for antibacterial activity against clinically relevant pathogens. Fungal isolates were identified through macromorphological characterization and sequence analysis of ITS and β-tubulin genes. Antibacterial activity of the guttation droplets was evaluated using agar well diffusion and microbroth dilution assays to determine inhibition zones, minimum inhibitory volume (MIV), and minimum bactericidal volume (MBV). The exudates exhibited measurable activity against several Gram-negative and Gram-positive bacteria, including Escherichia coli, Salmonella enterica, Klebsiella pneumoniae, Serratia marcescens, and Staphylococcus aureus. Guttation droplets from P. pimiteouiense showed the highest inhibition, with zones up to 24.4 mm against S. enterica, and activity comparable to gentamicin. MBV/MIV ratios indicated bactericidal activity against selected pathogens, including E. coli, K. pneumoniae, and S. aureus. These findings demonstrate that fungal guttation droplets represent a promising and underexplored source of antibacterial compounds and support their potential for antimicrobial discovery.
Barajas-Saucedo et al. (Fri,) studied this question.