Vietnamese herbal extracts exhibit potent antibacterial activity against Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease in shrimp aquaculture.

Acute hepatopancreatic necrosis disease (AHPND), caused byVibrio parahaemolyticus, poses a critical threat to global shrimp aquaculture. This study evaluated antimicrobial efficacy of ten Vietnamese herbal extracts against multidrug-resistant AHPND-causingV. parahaemolyticus(VpAHPND) isolates from diseased white-leg shrimp (Litopenaeus vannamei) in Vinh Long, Vietnam. Three field isolates with complete intrinsic β-lactam resistance and acquired resistance to multiple antibiotics were cultured and characterized via nested PCR and antimicrobial susceptibility testing. Among conventional antibiotics, levofloxacin showed superior efficacy (28.22 ± 2.79 mm at 50 ppm), while most alternatives demonstrated reduced activity. Remarkably, herbal extracts demonstrated comparable or superior antimicrobial efficacy:Lagerstroemia speciosaexhibited the strongest activity (25.67 ± 0.58 mm inhibition zone), with minimum inhibitory concentration (MIC) values of 0.19-0.39 mg/mL and bactericidal minimum bactericidal concentration/MIC ratios of 2-3.Limnophila aromaticashowed substantial activity (18.33 ± 0.58 mm), with MIC values of 0.78-1.56 mg/mL and MBC/MIC ratios of 3-4. Qualitative phytochemical screening identified alkaloids, flavonoids, steroids, triterpenoids, tannins, saponins, and sesquiterpene lactones in both extracts. Quantitative analysis revealedL. speciosacontained significantly higher polyphenolic (53.1 ± 2.8 mg GAE/g) and flavonoid (195.2 ± 6.8 mg QE/g) contents compared toL. aromatica(48.7 ± 2.1 mg GAE/g and 182.4 ± 5.3 mg QE/g, respectively). This research establishes a crucial foundation for identifying abundant Vietnamese medicinal plants as viable plant-based alternatives for managing antibiotic-resistant VpAHPND in sustainable aquaculture.These findings establishL. speciosaandL. aromaticaas viable plant-based alternatives for managing antibiotic-resistant VpAHPND in sustainable aquaculture, particularly for strains with accumulated acquired resistance mechanisms.