At present, the paucity of new antimicrobials coming into the market has led to the problem of antibiotic resistance fast escalating into a global health crisis. Diverse on metabolic, genetic and physiological fronts, rapid progression of resistant microbes and the lack of a strategic management plan have led researchers to consider plant-derived substances (PDS) as alternative or in complementing antibiotics against the diseases, thus the aim of this study was to assess the antibacterial effect of black seed (Nigella sativa) and clove (Siyzigium aromaticum) seed extracts and their synergistic action against some selected pathogenic bacteria; namely: Klebsiella pneumoniae, Staphylococcus aureus, Salmonell typhi and clinical isolates and their standard derivatives. Ethanol, hexane, acetone and chloroform crude extracts of N. sativa and S. aromaticum were evaluated against tested pathogenic bacteria using agar well diffusion method; the inhibitory zones were recorded in millimeters. Ciprofloxacin was used as positive controls, while dimethyl sulfooxide (DMSO) 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 N. sativa crude extract against all clinical isolate and standard pathogenic bacteria ranged from (12-30 mm). The inhibition zone of all S. aromaticum crude extract against all clinical and standard pathogenic bacteria ranged from (12-32 mm). N. sativa hexane extract against E.coli (clinical isolate) exhibited the lowest inhibition zone while acetone extract against S. aureus (ATCC25923) exhibited the highest inhibition zone. S. aromaticum chloroform extract against S. aurues (clinical isolate) exhibited the lowest inhibition zone while ethanol extract against S. aureus (ATCC25923) exhibited the highest inhibition zone. The synergistic antibacterial effect of N. sativa and S. aromaticum crude extract against both clinical isolate and standard pathogenic bacteria ranged from (12-33 mm). The inhibition zone of the synergistic antibacterial effect of N. sativa and S. aromaticum seed extracts against tested pathogenic bacteria was significantly (P value ranges from 0.01 to 0.03) greater than the extracts used separately. Thus, the present finding supports the traditional use of these plants in combination for treating pathogens. 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. The result of phytochemical screening also showed that the plants contain trepenoids, tannin, flavonoids and saponins except acetone extract of both plants which could not show the presence of flavonoids.
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