Antibacterial activity of palmarosa oil significantly varies between Aeromonas veronii and Aeromonas caviae and exhibits selective action on tetracycline and sulfonamide resistant A. caviae

Identification of essential oils with strong activity against stationary phase Mycobacterium abscessus

Purpose

To identify essential oils (EOs) active against non-growing stationary phase Mycobacterium abscessus and multidrug-resistant M. abscessus strains.

Methods

The activity of EOs against both stationary and log phase M. abscessus was evaluated by colony forming unit (CFU) assay and minimum inhibitory concentration (MIC) testing.

Results

We assessed the activity of 80 EOs against stationary phase M. abscessus and found 12 EOs (Cinnamon, Satureja montana, Palmarosa, Lemon eucalyptus, Honey myrtle, Combava, Health shield, Mandarin, Thyme, Rosewood, Valerian Root and Basil) at 0.5% concentration to be active against both growing and non-growing stationary phase M. abscessus. Among them, Satureja montana essential oil and Palmarosa essential oil could eliminate all stationary phase M. abscessus at 0.125% and Cinnamon essential oil could eliminate stationary phase bacteria at 0.063% after 1-day treatment. Interestingly, these EOs also exhibited promising activity against multidrug-resistant M. abscessus clinical strains.

Conclusions

Our study indicates that some EOs display outstanding effectiveness against both drug susceptible M. abscessus and multidrug-resistant M. abscessus isolates. These findings may be significant for the treatment of persistent M. abscessus infections.

Anthelmintic Efficacy of Palmarosa Oil and Curcuma Oil against the Fish Ectoparasite Gyrodactylus kobayashii (monogenean)

Monogeneans are a serious threat to the development of aquaculture due to the severe economic losses they cause. The prevention and treatment of this disease are increasingly difficult because of the environmental and health concerns caused by the use of chemical anthelmintics and the emergence of drug resistance. It is thus necessary to search for effective alternatives for the treatment of monogenean infections. In the current study, anthelmintic efficacy of 16 selected essential oils (EOs) was investigated using the goldfish (Carassius auratus)–Gyrodactylus kobayashii model. The screening experiment indicated that palmarosa oil and curcuma oil had satisfactory anthelmintic activity against G. kobayashii with EC100 values of 10 and 12 mg/L after 24-h exposure, respectively. The in vivo and in vitro assays indicated anthelmintic efficacy of palmarosa oil against G. kobayashii was in a time and dose-dependent manner. Interestingly, curcuma oil showed an anesthetic effect on G. kobayashii, and its anthelmintic activity was dose-dependent rather than time-dependent in the concentration range tested in this study. Additionally, the 24-h LC50 (50% lethal concentration) against goldfish of these two EOs was 8.19-fold and 5.54-fold higher than their corresponding EC50 (50% effective concentration) against G. kobayashii, respectively. Moreover, exposure to these two EOs at 100% effective concentration against G. kobayashii had no serious physiological and histopathological influence on goldfish. These results demonstrated a high safety for goldfish of these two EOs. Overall, palmarosa oil and curcuma oil could be potential candidates for the treatment of G. kobayashii infections in aquaculture.