The Crohnie

Antibacterial Activities of Naturally-Occurring Compounds against Mycobacterium avium subspecies paratuberculosis.
Wong SY, Grant IR, Friedman M, Elliott CT, Situ C.

http://aem.asm.org/cgi/content/abstract/AEM.00981-08v1
http://www.ncbi.nlm.nih.gov/pubmed/18676709

Antibacterial activities of 18 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 microg/ml mycobactin J supplemented with five concentrations of each test compound. The changes in optical density (OD) of the cultures at 600 nm as a measure of CFUs was recorded at intervals over an incubation period of 42 days at 37 degrees C. 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 microg/ml, then cinnamon oil (26.2 microg/ml), oregano (68.2 microg/ml), carvacrol (72.2 microg/ml), 2,5-dihydroxybenzaldehyde (74 microg/ml), and 2- hydroxy-5-methoxybenzaldehyde (90.4 microg/ml). With the exception of carvacrol, a phenolic compound, three of the four most active compounds are aldehydes, suggesting that the structure of the phenolic group or 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.

It appears that some Azathioprine and 6-MP, which are used for the treatment of Crohn’s Disease, and whose mechanism of action is currently unknown, have antibiotic activity against Mycobacterium avium subspecies paratuberculosis (MAP).

http://www.paratuberculosis.org/pubs/proc9/abst182f_o6.htm

As noted by the authors, “These data may partially explain the paradoxical response of Crohn’s disease patients infected with M. paratuberculosis to treatment with immunosuppressive thiopurine drugs i.e. they do not worsen with anti-inflammatory treatment as would be expected with a microbial etiologic pathogen.”
=======================================

The in vitro susceptibility of human and bovine-origin Mycobacterium paratuberculosis to the thiopurine drugs 6-mercaptopurine (6-MP) and azathioprine (AZA) were established using conventional plate counting methods and the MGIT 960 ParaTB culture system. Both 6-MP and AZA had antibacterial activity against M. paratuberculosis; isolates from Crohn’s disease patients tended to be more susceptible than were bovine-origin isolates. Isolates of Mycobacterium avium, used as controls, were generally resistant to both AZA and 6-MP even at high concentrations (>=64.0 microg/mL). Among rapidly growing mycobacteria, M. phlei was susceptible to 6-MP and AZA whereas M. smegmatis strains were not. AZA and 6-MP limited the growth of, but did not kill, M. paratuberculosis in a dose-dependent manner. Anti-inflammatory drugs in the sulfonamide family (sulfapyridine, sulfasalazine, and 5-amino- salycilic acid (mesalamine)) had little or no antibacterial activity against M. paratuberculosis. The conventional antibiotics azithromycin and ciprofloxacin (CPX) used as control drugs were bactericidal for M. paratuberculosis, exerting their killing effects on the organism relatively quickly. Simultaneous exposure of M. paratuberculosis to 6- MP and CPX resulted in significantly higher CFUs as compared to use of CPX alone. These data may partially explain the paradoxical response of Crohn’s disease patients infected with M. paratuberculosis to treatment with immunosuppressive thiopurine drugs i.e. they do not worsen with anti-inflammatory treatment as would be expected with a microbial etiologic pathogen. These findings also should influence the design of therapeutic trials to evaluate antibiotic treatments of Crohn’s disease: azathioprine drugs may confound interpretation of data on therapeutic responses both antibiotic-treated and control groups.