In vitro antibiofilm activity of resveratrol against avian pathogenic Escherichia coli

Background Avian pathogenic Escherichia coli (APEC) strains cause infectious diseases in poultry. Resveratrol is extracted from Polygonum cuspidatum, Cassia tora Linn and Vitis vinifera, and displays good antimicrobial activity. The present study aimed to investigate the antibiofilm effect of resveratrol on APEC in vitro. The minimum inhibitory concentration (MIC) of resveratrol and the antibiotic florfenicol toward APEC were detected using the broth microdilution method. Then, the effect of resveratrol on swimming and swarming motility was investigated using a semisolid medium culture method. Subsequently, the minimum biofilm inhibitory concentration (MBIC) and the biofilm eradication rate were evaluated using crystal violet staining. Finally, the antibiofilm activity of resveratrol was observed using scanning electron microscopy (SEM). Meanwhile, the effects of florfenicol combined with resveratrol against biofilm formation by APEC were evaluated using optical microscopy (OM) and a confocal laser scanning microscopy (CLSM). Results The MICs of resveratrol and florfenicol toward APEC were 128 mu g/mL and 64 mu g/mL, respectively. The swimming and swarming motility abilities of APEC were inhibited in a resveratrol dose-dependent manner. Furthermore, resveratrol showed a significant inhibitory activity against APEC biofilm formation at concentrations above 1 mu g/mL (p < 0.01). Meanwhile, the inhibitory effect of resveratrol at 32 mu g/mL on biofilm formation was observed using SEM. The APEC biofilm was eradicated at 32 mu g/mL of resveratrol combined with 64 mu g/mL of florfenicol, which was observed using CLSM and OM. Florfenicol had a slight eradication effect of biofilm formation, whereas resveratrol had a strong biofilm eradication effect toward APEC. Conclusion Resveratrol displayed good antibiofilm activity against APEC in vitro, including inhibition of swimming and swarming motility, biofilm formation, and could eradicate the biofilm.