Synergistic Activity of Cressa cretica Extract Combination with Ampicillin against Klebsiella pneumoniae

Aims: This study was conducted to evaluate the synergistic effect of ethanolic extract of Cressa cretica and ampicillin against the standard and multidrug-resistant (MDR) strains of Klebsiella pneumoniae. Method: The chemical composition of the ethanolic extract of C. cretica was determined by high-performance liquid chromatography (HPLC). The minimum inhibitory concentration (MIC) of the extract was used to evaluate the antimicrobial performance of the extract. The checkboard broth method was used to investigate the synergistic effect of the extract with ampicillin. Results: The ethanolic extract of C. cretica inhibited the growth of the standard strain of K. pneumoniae with MIC 100 mg/mL and did not affect the MDR strains of K. pneumoniae. The Fractional inhibitory concentration (FIC) showed an additive effect of ampicillin in combination with C. cretica on the standard strain of K. pneumoniae. The MIC of ampicillin in combination with C. cretica was reduced eightfold. Conclusion: C. cretica ethanolic extract is containing chlorogenic acid, rutin, and catechin. The extract in combination with ampicillin can reduce the minimum inhibitory concentration of ampicillin. C. cretica ethanolic extract can reduce the ampicillin dosage in the treatment of Klebsiella-induced infections.