Table 1.

Antibacterial effects of Nigella sativa

Extract	Method	Gram-positive bacteria	Gram-negative bacteria	Control	Main findings	References
Aqueous extract of seeds	Standard killing curve	Not available	H. pylori	H. pylori with sterile distilled water	100% of inhibition of growth after 60-min incubation against all seven strains.	[21]
Oil and crude extract	Well diffusion assay and broth dilution method	Not available	Six strains of Salmonella	Antibiotic susceptibility test against 50 and 100 μg/ml ciprofloxacin and ceftriaxone	All Salmonella strains were susceptible to the crude extract. 90% of resistant Salmonella strains were sensitive to the oil extract.	[20]
Essential oil extract in microdilution	Agar well diffusion	S. aureus, B. cereus, L. monocytogenes	S. typhimurium, E. coli, P. aeruginosa	Eugenol microemulsion and ceftriaxone	EO showed its high antibacterial activity in the concentration of 100 μg EO/well against S. aureus and B. cereus. At 500 μg EO/well effective against E. coli (20.2 mm) and S. typhimurium (26.5 mm). L. monocytogenes and P. aeruginosa were resistant to EO at all concentrations.	[11]
Essential oil and petroleum ether extract	Agar well diffusion	S. aureus, two strains of B. cereus	E. coli and P. aeruginosa	Gentamycin sulfate	The petroleum ether extract (500 mg/ml) exceeded the zone of inhibition of gentamycin in both tested strains of B. cereus. P. aeruginosa was resistant to both plant extracts.	[22]
Oil extract	Disc diffusion and well diffusion method	MRSA	Not available	Antibiotic susceptibility test	62% of tested MRSA strains were susceptible to N. sativa oil.	[23]
Ethanolic extract	Broth microdilution test and agar well diffusion test	VRSA	Not available	Linezolid, moxifloxacin, clindamycin	Highest inhibition of growth (26 mm) was achieved at 20 mg/well (ethanolic extract) for five VRSA isolates.	[24]
Ethanolic extract	Disc and agar dilution method	MRSA	Not available	Unknown	All MRSA strains were susceptible to the ethanolic extract at 4 mg/disc.	[25]