Exploring plant compounds as enhancers of ciprofloxacin activity against planktonic and biofilm cells of poultry-related enterobacteriaceae.

This study evaluated the antimicrobial and antibiofilm activities of ciprofloxacin (Cip) in combination with trans-cinnamaldehyde (Tc), geraniol (Ger), and eugenol (Eug) against multidrug-resistant Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae isolated from broiler feces. Disk diffusion and microdilution assays showed that Tc displayed the highest antibacterial activity in disk diffusion (IZD: 30 mm) and microdilution assays (MIC: 312.5 μg/mL), while Ger and Eug revealed smaller inhibition zones (∼9-12 mm) and higher MIC values (2500 μg/mL). Checkerboard assays indicated that Ger and Eug synergized with Cip (FICi ≤0.5), decreasing Cip MIC by up to 130-fold. The combinations of Cip with Eug and Ger led to a 100 % and 90 % reduction in biofilms, respectively. These findings suggest that plant compounds, particularly Ger and Eug, enhance the efficacy of Cip against both planktonic and biofilm cells, presenting a promising strategy to combat antibiotic resistance in poultry farming.