GC–MS characterisation and antibacterial activity evaluation of <i>Nigella sativa</i> oil against diverse strains of <i>Salmonella</i>

<div><p><i>Salmonella</i> resistance is becoming a worldwide serious health issue in these days; therefore, it is an urgent need to develop some alternative approaches to overcome this problem. Twenty bacterial strains were isolated and purified from different environmental sources and confirmed as <i>Salmonella</i> by morphological and biochemical analyses. Further confirmation was done by 16s rRNA sequencing. Antibiotic susceptibility test was performed by well diffusion assay against different concentrations of Ceftriaxone and Ciprofloxacin. The behaviour of both antibiotics was different against diverse strains of <i>Salmonella</i>. <i>Salmonella</i> strains resistant to both antibiotics were analysed for antibacterial activity of natural extracts of <i>Nigella sativa</i> (black seeds). <i>N</i>.<i> sativa</i> oil was found to be more effective against <i>Salmonella</i> species for which even Ceftriaxone and Ciprofloxacin were ineffective. Gas chromatography and mass spectrometry analysis of <i>N</i>.<i> sativa</i> oil was also accomplished, exhibiting 10 compounds including thymoquinone, <i>p</i>-cymene, <i>c</i><i>is</i>-carveol, thymol, α-phellandrene, α-pinene, β-pinene, <i>trans</i>-anethole, α-longipinene and longifolene.</p>