Additive Antibacterial Activity of Coriandrum sativum Ethanolic Extract in Combination with Conventional Antibiotics Against Staphylococcus aureus and Klebsiella pneumoniae

Abstract

As antibiotic resistance becomes more widespread, alternative and complementary antimicrobial approaches are highly needed. This study evaluated the in vitro antibacterial activity of ethanolic extract of Coriandrum sativum (CS) leaves alone and in combination with standard antibiotics, including penicillin, ampicillin, tetracycline, and gentamycin, against Staphylococcus aureus and Klebsiella pneumoniae. We studied the antibacterial activity by determining the minimum inhibitory concentration (MIC) with the broth microdilution method and interaction studies using a combination assay with Gentamicin and Vancomycin. The extract showed inhibitory activity against Staphylococcus aureus and Klebsiella pneumoniae, with minimum inhibitory concentrations (MICs) of 62.5 µg/ml and 125 µg/ml, respectively. Gentamicin and vancomycin exhibited anticipated antibacterial profiles; specifically, vancomycin was inactive against Klebsiella pneumoniae. Combination studies demonstrated that the extract potentiated the antibacterial activity of gentamicin against both bacterial strains, increasing the effective concentrations of both agents. The fractional inhibitory concentration indices calculated suggested additive interactions. However, vancomycin did not show a significant improvement. Such findings suggest that the extract of Coriandrum sativum (including the powdered form) could be a potential natural adjunct to conventional antibiotics, especially aminoglycosides, in order to ameliorate antibacterial efficacy. More studies are needed to understand the mechanisms and assess clinical applicability.