Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/22/2008
Publication Date: 10/1/2008
Publication URL: http://dx.doi.org/10.1128/AEM.00981-08
Citation: Wong, Y.Y., Grant, I., Friedman, M., Elliot, C.T., Situ, C. 2008. Antibacterial Activities of Naturally occurring Compounds against Mycobacterium avium subspecies paratuberculosis. Applied and Environmental Microbiology. 74:5986-5990. Interpretive Summary: Mycobacterium avium subspecies paratuberculosis (Map) is the causative agent of Paratuberculosis, also known as Johne’s disease, in wild and domestic ruminants, especially dairy cattle. Map may also contribute to the development of Crohn’s disease (irritable bowl syndrome) in humans. Johne’s disease is a chronic granulomatous enteropathy, the clinical signs of which include chronic diarrhea, progressive weight loss, decreased milk production, and infertility. There is currently no approved drug or treatments for Johne’s disease. Once farm animals are infected by Map, they would be culled early. This leads to economic losses to livestock and dairy producers due to reduced productivity, animal wasting, and mortalities in severe cases. Milk could be contaminated with Map as it is systemic or by feces from infected animals during milking. Recent studies have shown that Map would survive pasteurization, which might bring risks to human health. To our knowledge, the present study represents the first evaluation of the activity of naturally-occurring compounds against Map, an important animal pathogen and potential human pathogen. In a collaborative study carried out at Queen’s University in Belfast, UK, we found that several natural compounds we previously found at this laboratory to inactivate foodborne pathogens also inactivated three strains of Map, a bovine isolate, a raw milk isolate, and a human isolate. Whether the newly discovered anti-Map compounds can protect against adverse effects of both Johne’s and Crohn's diseases merits further study.
Technical Abstract: Antibacterial activities of 19 naturally-occurring compounds (including essential oils and some of their isolated constituents, apple and green tea polyphenols and other plant extracts) against three strains of Mycobacterium avium subspecies paratuberculosis (Map), a bovine isolate NCTC 8578, a raw milk isolate 806R, and a human isolate ATCC 43015, were evaluated using a macrobroth susceptibility testing method. Map was grown in 4 ml Middlebrook 7H9 broth containing 10% OADC, 0.05% Tween 80 (or 0.2% glycerol) and 2 µg/ml mycobactin J supplemented with five concentrations of each test compound. The changes in optical density of the cultures at 600 nm as a measure of CFUs were recorded at intervals over an incubation period of 42 days at 37oC. Six of the compounds were found to inhibit the growth of Map. The most effective compound was trans-cinnamaldehyde with a minimum inhibitory concentration (MIC) of 25.9 µg/ml, then cinnamon oil (26.2 µg/ml), oregano oil (68.1 µg/ml), carvacrol (72.2 µg/ml), 2,5-dihydroxybenzaldehyde (74.0 µg/ml), and 2-hydroxy-5-methoxybenzaldehyde (90.3 µg/ml). With the exception of carvacrol, the results suggest that for three of the four most active compounds, the structure of the aldehyde group may be important to the antibacterial activity. No difference in compound activity was observed between the three Map strains studied. Possible mechanisms of the antimicrobial effects are discussed.