An investigation of the bactericidal activity of selected essential oils to Aeromonas spp.

Abstract

Diseases of fishes caused by Aeromonas spp. are common, have broad host ranges and may cause high mortality. Treatments of captive-reared populations using antimicrobials are limited with concerns for bacterial resistance development and environmental dissemination. This study was done to determine whether selected plant-derived essential oils were bactericidal to Aeromonas spp. Initially, twelve essential oils were evaluated using a disk diffusion assay to an isolate of A. salmonicida subsp. salmonicida, cause of fish furunculosis. The greatest zones of inhibition were obtained with oils of cinnamon Cinnamomum cassia, oregano Origanum vulgare, lemongrass Cymbopogon citratus and thyme Thymus vulgaris. Minimum bactericidal concentrations (MBC’s) were determined for these four oils, Allimed® (garlic extract, Allium sativum) and colloidal silver to sixty-nine isolates representing nine Aeromonas spp. The lowest mean MBCs (0.02–0.04%) were obtained with three different sources of cinnamon oil. MBCs for three sources of oregano and lemongrass oils ranged from 0.14% to 0.30% and 0.10% to 0.65%, respectively, and for two thyme oils were 2.11% and 2.22%. The highest concentration (5%) of Allimed® tested resulted in MBCs to twelve isolates. A concentration of silver greater than 15 mg/L would be required to determine MBCs for all but one isolate.

Edible antimicrobial films based on microencapsulated lemongrass oil

“…Besides, 53.6 % pseudomonads, 53.1 % streptococci and 50 % of Budvicia aquatica and Leminorella ghirmontii strains were also sensitive to LMO. In general, the antimicrobial properties of LMO and its practical application potential are comparable to oregano oil and only surpassed by thyme oil (Starliper et al 2015).…”

“…Among them thyme oil, oregano oil and, lately, lemongrass oil have been evaluated for their antioxidant and antimicrobial properties (Tongnuanchan and Benjakul 2014). There are several reports where different bacteria have been tested for their sensitivity to LMO components (Taweechaisupapong et al 2012;Starliper et al 2015;Olorunnisola et al 2014). In one of the most extensive studies, Singh et al (2011) tested the antimicrobial activity of LMO against 1114 strains belonging to 29 genera and 105 species of microbes (molds, yeasts and bacteria) isolated from clinical cases, environment (water, air, soil, droppings of lizards and birds), food and healthy animals.…”

Comparative in vitro efficacy of eight essential oils as antibacterial agents against pathogenic bacteria isolated from pet-turtles

“…In line with our results, a previous study reported MBC values of around 0.31% (v/v) in fish-borne Aeromonas spp. (Starliper et al 2015). In contrast, lemongrass oil exerted only a minor effect on C. freundii and P. mirabilis and a lower number of isolates were found to be susceptible (Singh et al 2011).…”

Egg surface decontamination with bronopol increases larval survival of Nile tilapia, Oreochromis niloticus

“…This bacterium is recognized as an opportunistic pathogen that can be commonly found in hatchery water causing a substantial damage to the hatchery production of many freshwater fish species under artificial incubation conditions (Hanninen et al 1997). The occurrence and severity of bacterial outbreaks during the hatching stages are dependent on the water source, water temperature, organic load, and incubation period (Starliper et al 2015). 6 CFU/g) were acceptable within the ranges of bacteria colonized on the surface of salmonid eggs (10 3 -10 6 CFU/g) (Austin 2006), however the viable counts in freshwater tilapia eggs taken in this study were higher than those in marine fish eggs.…”