Antibacterial effect of essential oregano oil (Lippia berlandieri ) on pathogenic bacteria of shrimp Litopenaeus vannamei

Abstract

An alternative for antibiotics use is the employment of vegetal oil extracts with unspecific antagonistic activity. In the present study, two fractions of essential oil from the oregano Lippia verlandieri, fraction high in thymol (FT) and fraction high in carvacrol (FC) were evaluated and compared to commercial antibiotics for the bacteria Aeromonas hydrophila, A. salmonicida, Pseudomonas putida, P. fluorescens, Vibrio mimicus, V. alginolyticus, V. fluvialis y V. vulnificus, isolated from shrimp Litopenaeus vannamei. The minimal inhibitory concentration (MIC) as well as the inhibition capacity in agar plates of these antimicrobials were evaluated and compared to commercial antibiotics. The survival of shrimp infected with V. alginolyticus and treated with the antimicrobials FT, FC and the antibiotic Enrofloxacine was also tested. The MIC of the FT and FC were from 50 to 100 µg/mL, the commercial antibiotic showed a MIC from 10 to 50 µg/mL. V. alginolyticus had the highest (p ? 0.05) sensitivity level (50 to 56 mm of inhibitory halo) with FC and Enrofloxacine. Shrimp survival was 70, 50 y 50% with application of FC, FT and Enrofloxacine, respectively. Both FT and FC fractions are able to control in vitro growth of pathogenic bacteria in shrimp. It was concluded that the fraction high in carvacrol from essential oregano oil, could be a viable alternative or a suplement to commercial antibiotics for the control of Vibrio spp. pathogens in penaeid shrimps.