Vanilla modulates the activity of antibiotics and inhibits efflux pumps in drug-resistant Pseudomonas aeruginosa

Vanilla, a popular flavour extracted from Vanilla planifolia pods was tested for its antibiotic modulatory activity against extensively drug-resistant (XDR) Pseudomonas aeruginosa clinical isolates. Cured vanilla pod extract (VPE) was found non-bactericidal even at high doses (> 2000 µg/mL), however, it modulated the activity of several antibiotics at a sub-inhibitory concentration of 500 µg/mL. This modulation activity of VPE was observed for last line antibiotic options such as meropenem and tigecycline, as well as commonly used antibiotics like ciprofloxacin, levofloxacin and chloramphenicol. Further, it was observed that VPE inhibited the activity of efflux pumps in XDR P. aeruginosa clinical isolates. GC-MS spectral analysis revealed the dominance of vanillin, furfuran and some short-chain fatty acids in VPE. Therefore, further studies on the constituent ingredients in VPE are recommended to identify the active compounds and use them as antibiotic modulators and efflux pump inhibitors.