Thiopurine Drugs Azathioprine and 6-Mercaptopurine Inhibit Mycobacterium paratuberculosis Growth In Vitro

Abstract

The in vitro susceptibility of human-and bovine-origin Mycobacterium paratuberculosis to the thioupurine drugs 6-mercaptopurine (6-MP) and azathioprine (AZA) was 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 g/ml). Among rapidly growing mycobacteria, Mycobacterium phlei was susceptible to 6-MP and AZA whereas Mycobacterium 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-aminosalycilic acid [mesalamine]) had little or no antibacterial activity against M. paratuberculosis. The conventional antibiotics azithromycin and ciprofloxacin, 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 ciprofloxacin resulted in significantly higher CFU than use of ciprofloxacin 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 microbiological etiologic pathogen. These findings also should influence the design of therapeutic trials to evaluate antibiotic treatments of Crohn's disease: AZA drugs may confound interpretation of data on therapeutic responses for both antibiotic-treated and control groups.

Deciphering the Function of New Gonococcal Vaccine Antigens Using Phenotypic Microarrays

“…Growth of the Δngo1344 mutant was attenuated by 6-mercaptopurine at concentrations 1 and 2. This compound is typically used as an immunosuppressant in patients with Crohn's disease but has also been shown to suppress the growth of Mycobacterium paratuberculosis, a possible cause or trigger of Crohn's disease (91). The Δngo1344 mutant was also negatively affected by both colistin and 2-nitroimidazole.…”

Growth of M. avium Subspecies Paratuberculosis in Culture Is Enhanced by Nicotinic Acid, Nicotinamide, and α and β Nicotinamide Adenine Dinucleotide

“…It is that multiple agents used in the treatment of IBD are in fact antiMAP antibiotics. They are conventionally called ''antiinflammatories'' [29] and ''immuno modulators'' [30][31][32][33]. Analogous to the multiple clinical manifestations of leprosy [22,34], we additionally suggest that all of IBD may be caused by MAP [16,22,26].…”

Azathioprine, Mercaptopurine, and 5-Aminosalicylic Acid Affect the Growth of IBD-Associated Campylobacter Species and Other Enteric Microbes

“…This is supported by previous studies showing AZA and MP also inhibited the growth of Mycobacterium avium subsp. paratuberculosis , another bacterium that is associated with human CD (Sanderson et al, 1992; Collins et al, 2000; Sieswerda and Bannatyne, 2006; Greenstein et al, 2007; Shin and Collins, 2008). …”