Nigella sativa oil extract: A natural novel specific conjugal transfer inhibitor of vancomycin resistance from vanA/B-resistant Enterococcus faecium to Staphylococcus aureus

Aim The emergence of vancomycin-resistant Staphylococcus aureus (VRSA) has been identified as one of the most challenging problems in healthcare settings worldwide. Specific conjugation inhibitors' development is critical in the fight against the spread of emerging VRSA. The impact of Nigella sativa oil on VR genes conjugal transfer from Enterococcus faecium (VREtfm) to vancomycin-sensitive S. aureus (VSSA) was investigated in this study. Methods and Results Enterococciwere isolated from retail broilers, fish, cows' milk, and human urine. VR E. faecalis and VREtfm VanA phenotypes were prevalent in retail broiler samples. The VREtfm isolates were dominant, exhibiting high levels of resistance to gentamycin and ciprofloxacin antibiotics, as well as the existence of both vanA and vanB genes and virulence traits (ESP+, asa1(+)) as determined by PCR. VREtfm strains containing vanA/vanB genes and transconjugants containing 20 Kb plasmids (transfer frequency around 10(3)) and carrying the Tn1546 transposon were identified. Tn1546 transposon transfer with its VR markers to VSSA was effectively inhibited in treated VREtfm donor strains with a sub-minimum inhibitory concentration) of N. sativa oil. The Significance and Impact of the Study This work offers new insights for overcoming VR conjugal transfer utilizing natural N. sativa oil, as well as a suggestion for a novel specialized conjugation inhibitor that could effectively facilitate the difficulty of eliminating VR bacteria from healthcare settings.