Anti-Shigella activity and killing kinetics of compounds from MMV Pathogen and COVID Boxes: Identifying leads against Shigellosis.

BACKGROUND

Shigellosis is a leading diarrheal disease, posing critical public health challenges in low- and middle-income countries. Rising antibiotic resistance exacerbates treatment limitations.

METHODS

We screened 560 compounds from the MMV Pathogen and COVID Boxes for in vitro activity against Shigella flexneri, S. sonnei, and S. dysenteriae via resazurin-based microdilution. Cytotoxicity (RAW 264.7 cells) and killing kinetics against S. flexneri were assessed.

RESULTS

From the primary screen, 13 compounds (9 from the Pathogen Box, 4 from the COVID Box) showed potent anti-Shigella activity against S. flexneri (MIC ≤10 μM). Among these, seven non-antibiotic Pathogen Box compounds exhibited low-micromolar MICs (0.31-5 μM) and low cytotoxicity (CC50 > 100 μM). The known antibiotic levofloxacin (MMV687798) showed broad-spectrum activity (MIC 0.15-2.5 μM). MMV1804312 (salinomycin) was the most active COVID Box hit (MIC 1.25 μM). Time-kill assays revealed rapid, concentration-dependent bactericidal activity (≥3-log reduction within 4-6 h) for Pathogen Box compounds MMV675997 and MMV021660, while MMV000858 displayed bacteriostatic action.

CONCLUSION

This study identifies several novel, non-antibiotic leads from the MMV Pathogen Box with potent anti-Shigella activity and favorable cytotoxicity profiles, offering promising starting points for further development against drug-resistant shigellosis.