Antimicrobial and antibiofilm activity of selected flavonoids against pathogenic Leptospira species

Leptospirosis is a widespread zoonotic disease where biofilm formation significantly hinders treatment, contributing to chronic infections. This preliminary study evaluated the antimicrobial and antibiofilm properties of four flavonoids-apigenin, xanthohumol, quercetin, and luteolin-against Leptospira santarosai (sv. Guaricura), L. interrogans (sv. Copenhageni and Hardjoprajitno), and L. borgpetersenii (sv. Hardjobovis). Using microdilution methods, quercetin and apigenin exhibited superior antimicrobial activity, reaching MICs of ≤ 0.12 µg/mL for L. santarosai sv. Guaricura. In antibiofilm assays, quercetin was the most effective compound, successfully disrupting biofilm at minimal biofilm disruptive concentrations (MBDC) as low as < 0.0012 µg/µL for L. santarosai sv. Guaricura and for L. interrogans sv. Copenhageni and Hardjoprajitno. These findings highlight the potential therapeutic candidates, requiring further evaluation, for managing both acute and persistent forms of leptospirosis, either alone or as adjuvants to current antibiotic therapies. Further in vivo studies are warranted to confirm their therapeutic safety and clinical efficacy.