Mechanisms of Antimicrobial Action of Cinnamon and Oregano Oils, Cinnamaldehyde, Carvacrol, 2,5-Dihydroxybenzaldehyde, and 2-Hydroxy-5-Methoxybenzaldehyde against Mycobacterium avium subsp. paratuberculosis (Map).

Stella Nowotarska,Irene Grant,Mendel Friedman,Christopher Elliott,Krzysztof Nowotarski,Chen Situ

doi:10.3390/foods6090072

Abstract

The antimicrobial modes of action of six naturally occurring compounds, cinnamon oil, cinnamaldehyde, oregano oil, carvacrol, 2,5-dihydroxybenzaldehyde, and 2-hydroxy-5-methoxybenzaldehyde, previously found to inhibit the growth of Mycobacterium avium subsp. paratuberculosis (Map) reported to infect food animals and humans and to be present in milk, cheese, and meat, were investigated. The incubation of Map cultures in the presence of all six compounds caused phosphate ions to leak into the extracellular environment in a time- and concentration-dependent manner. Cinnamon oil and cinnamaldehyde decreased the intracellular adenosine triphosphate (ATP) concentration of Map cells, whereas oregano oil and carvacrol caused an initial decrease of intracellular ATP concentration that was restored gradually after incubation at 37 °C for 2 h. Neither 2,5-dihydroxybenzaldehyde nor 2-hydroxy-5-methoxybenzaldehyde had a significant effect on intracellular ATP concentration. None of the compounds tested were found to cause leakage of ATP to the extracellular environment. Monolayer studies involving a Langmuir trough apparatus revealed that all anti-Map compounds, especially the essential oil compounds, altered the molecular packing characteristics of phospholipid molecules of model membranes, causing fluidization. The results of the physicochemical model microbial membrane studies suggest that the destruction of the pathogenic bacteria might be associated with the disruption of the bacterial cell membrane.

Highlights

Many naturally-occurring compounds, such as plant extracts, secondary metabolites, and phytochemicals, have been extensively evaluated for antimicrobial activity [1,2,3,4,5,6,7,8,9]
In a previous study we investigated the effect of a range of naturally-occurring compounds on Mycobacterium avium subsp. paratuberculosis (Map) cells
We explored the use of monolayers of bacterial phospholipids as artificial model membranes to study the interaction these compounds with the artificial cell membranes [63]

Summary

Introduction

Many naturally-occurring compounds, such as plant extracts, secondary metabolites, and phytochemicals, have been extensively evaluated for antimicrobial activity [1,2,3,4,5,6,7,8,9]. Foods 2017, 6, 72 compounds, e.g., cinnamon oil and oregano oil, have exhibited activity against pathogenic bacteria that have developed resistance to conventional antibiotics [21,22]. Map is a bacterial pathogen of animal health and potential public health significance [23]. As the causative agent of Johne’s disease (paratuberculosis) in domesticated ruminants, such as cattle, sheep, goats, and rabbits [24,25,26,27,28], as well as hens [29], starlings [30], and wildlife [31], it can cause chronic diarrhea, progressive weight loss, decreased milk production, and infertility in these food animals, as well as significant economic losses to farmers [32,33,34,35]. Vaccines in development have the potential to protect dairy herds against Map [39,40,41,42]

Methods

Discussion

Conclusion