Susceptibility Pattern of Plasmid-borne Vancomycin-Resistant Enterococcus faecalis Strains to Selected Nigerian Medicinal Plants

Objective: To determine whether the presence of the resistance factors (plasmids and vanA genes) will negatively aid the susceptibility of vancomycin-resistant Enterococcus faecalis (VREf) to medicinal plants.

Materials and Methods: Standard methods were used for the isolation and identification of the E. faecalis while antibiotic susceptibility of the isolates was determined by disc diffusion method. Extraction of the plasmid DNA was performed and identification of van genotype vanA was carried out by PCR. Anti-enterococcal activities of extracts of ten medicinal screened were determined by agar dilution test.

Results: All the vancomycin-resistant E. faecalis strains isolated were resistant to amoxicillin/clavulanic acid, ofloxacin, ciprofloxacin and levofloxaxin. Eight out of the nine VREf starins possessed plasmid with the molecular size ranging from 6557 to 23130 base pairs. Also only four out of the ten test organisms possessed vanA gene. All the ten medicinal plants screened had tannins and saponin but lack phlobatanin and cardic glycoside. Entada africana followed by Uvaria chamae showed pronounced effect on the isolates while Sarcocephalus latifolius had the least effect on the bacteria. Chloroform extracts was the most effective among the three extracts of medicinal plants followed by ethanolic while acetone extracts showed the least effectiveness.

Conclusion: The VREf susceptibility to the medicinal plants seems not to be influenced by the presence of the plasmid and vanA gene. The isolation of the anti-enterococcal compounds from the plants and their mode of action are still open to investigation.