Extracts of Bryophyllum pinnatum and Vincetoxicum rossicum synergize with standard antibiotics against multidrug-resistant gram-negative bacteria

Abstract

The increasing prevalence of antibiotic-resistant Gram-negative bacteria has intensified the need for alternative antimicrobial agents. This study evaluated the antibacterial activities of ethanolic extracts of Bryophyllum pinnatum and Vincetoxicum rossicum against clinical isolates of Escherichia coli, Klebsiella pneumoniae, and Salmonella typhi. The leaves were extracted using 95% ethanol, and their antibacterial efficacy was assessed using the agar well diffusion method on Mueller-Hinton agar, with standard antibiotics (Amoxicillin-Clavulanate, Cefuroxime, and Ceftazidime) as controls. Zones of inhibition were measured, and data were analyzed using two-way ANOVA with a P < 0.05 significance level. The ethanolic extract of V. rossicum at 100% concentration demonstrated significant antibacterial activity against E. coli (18.33 ± 0.33 mm), K. pneumoniae (15.33 ± 0.66 mm), and S. typhi (13.33 ± 0.33 mm). In B. pinnatum, the ethanolic extract at 100% concentration was active against E. coli (14.67 ± 0.33 mm) and K. pneumoniae (14.67 ± 0.90 mm) but showed no effect on S. typhi. Among the antibiotics, Ceftazidime produced the highest inhibition against E. coli (34.00 ± 0.58 mm), followed by Cefuroxime (29.75 ± 0.86 mm) and Amoxicillin–Clavulanate (28.25 ± 0.75 mm). Notably, synergistic effects against the bacterial isolates were observed between the ethanolic extract of V. rossicum and Ceftazidime (53.00 mm), and between Cefuroxime and Ceftazidime (45.00 mm). These findings suggest that ethanolic extracts of B. pinnatum and V. rossicum may serve as complementary agents in the treatment of infections caused by Gram-negative bacteria.