Tagetes lucida Cav. essential oil and the mixture of its main compounds are antibacterial and modulate antibiotic resistance in multi-resistant pathogenic bacteria.

We evaluated an essential oil (EO) of Tagetes lucida Cav. and the mixture of its main compounds against multi-drug resistant bacteria. We found that EO and the partially reconstituted blend of its main components have antibacterial activity and inhibit antibiotic resistance (ampicillin, chloramphenicol, nalidixic acid, vancomycin and imipenem) in strains of Staphylococcus aureus ATCC 29213 and Pseudomonas aeruginosa HIM-MR01. The T. lucida EO alone or added to the antibiotics showed antimicrobial activity against S. aureus and P. aeruginosa. The EO main bioactive compounds were methyl eugenol (relative abundance in EO: 46·15%), estragole (32·93%), linalool (2·48%) and geraniol (0·33%). The mixture (PREO) of those compounds at those proportions inhibited the growth of P. aeruginosa in 45% at 683·62 µg ml-1 and that of S. aureus in 51·7% at 39·04 µg ml-1 . The PREO had higher antibacterial and modulatory activities than the original EO. In conclusion, we overcame the unpredictability of EO activity (due to their natural variability) by determining which EO components inhibited bacteria and then producing a PREO to generate a reproducible mixture with predictable antibacterial and modulation of resistance activities. Thus, the PREO, and its components, show potential as alternatives to manage multidrug-resistant pathogens.

Antimicrobial Activity of Alternanthera caracasana.

The antimicrobial activity of different extracts of Alternanthera caracasana. HBK against 11 bacterial strains and 1 yeast strain was evaluated. The ethyl acetate extract showed antimicrobial activity against Staphylococcus aureus., Staphylococcus epidermidis., Bacillus subtilis., Sarcina lutea., and one strain of Vibrio cholerae.. There was no antimicrobial activity against Candida albicans.. As a bioactive compound, 7-methoxycoumarin was identified.