Synergistic antibacterial effect of Lepidium sativum and Coriandrum sativum against standard and drug resistant clinically isolated pathogenic bacteria

Emerging and increasing resistance to antibiotics has become a threat to public health globally. Spices and herbs are considered as rich source of bio-active antimicrobial compounds. Thus the aim of this study was to assess the antibacterial effect of Lepidium sativum and Coriandrum sativum seed extracts and their synergistic action against some selected pathogenic bacteria; namely: Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus pneumonia and Escherichia coli clinical isolates. Ethanol, methanol and chloroform crude extracts of L. sativum and C. sativum were evaluated against tested pathogenic bacteria using agar well diffusion method; the inhibitory zones were recorded in millimeters. Tetracycline and Vancomycin were used as positive controls, while sterile distilled water was served as negative control. The minimal inhibitory concentration (MIC) of the plant extracts against test bacteria were assessed using agar well dilution and broth dilution method; and then Minimum Bactericidal Concentration (MBC) was evaluated. The inhibition zone of all crude seed extracts of L. sativum ranged from 19.64-25.68 mm against S. pneumonia; and S. aureus were significantly (P value ranges from 0.02 to 0.04) greater than the inhibition zone of other clinical isolates. On the other hand, the inhibition zone (24.86 mm) of ethanol extract of C. sativum seed against K. pneumoniae was significantly (P= 0.01) greater than the rest clinical isolated test pathogenic bacteria. The results of this study also demonstrated that ethanolic extracts used against almost all test bacteria showed antimicrobial and synergistic effect with most antibiotics better than methanolic and chloroform extracts. The inhibition zone of the synergistic antibacterial effect of L. sativum and C. sativum seed extracts against tested pathogenic bacteria was significantly (P value ranges from 0.01 to 0.02) greater than the antibacterial agents L. sativum and C. sativum used separately. Thus, the present finding supports the traditional use of these plants in combination for treating pathogens by the community. And also there is a need for detailed scientific study of traditional knowledge to ensure that valuable therapeutic knowledge of some plants is preserved as well as to provide scientific evidence for their efficacies. Key words: Lepidium sativum, Coriandrum sativum, antimicrobial activity.