Dietary calcium modulates Mycobacterium paratuberculosis infection in beige mice

A 6-month study was conducted to evaluate the effects of feeding different levels of dietary calcium (Ca) on the persistence of Mycobacterium paratube rculosis infection using a mouse model. Beige mice, averaging 8 weeks of ag e, were randomly assigned to one of the following dietary treatments: 1) 0. 02% Ca, 2) 0.15% Ca, 3) 0.45% Ca, and 4) 1.0% Ca. Mice were infected intrap eritoneally with 10(8) CFU viable M. paratuberculosis for 1, 3, and 6 month periods. Plasma Ca levels was unaffected by dietary Ca (x = 7.3 mg/dl). Pl asma levels of 1,25(OH)(2)D-3 was elevated significantly in 0.02% and 0.15% Ca groups compared to other treatments at the end of each period, with the highest levels observed for 0.02% Ca mice and intermediate values for 0.15 % Ca mice. One month after infection, numbers of viable M. paratuberculosis cultured from the spleen were significantly reduced for 0.15% Ca mice, whe reas the number of bacteria isolated from the liver and mesenteric lymph no de (MLN) were higher for the 0.02% Ca group. There were no differences in b acterial numbers in the ileum although they tended to be higher for the 0.0 2% Ca group. Three months after infection, bacterial numbers in the spleen, ileum, and MLN did not differ across treatments, however, significantly lo wer numbers were found in the liver of 1.0% Ca mice. Reduced bacterial coun ts were also observed in the liver of 0.15%, 0.45%, and 1.0% Ca mice after a 6-month infection period compared to the 0.02% Ca group, with the lowest numbers isolated from the 1.0% Ca mice. Numbers of viable bacteria cultured from the ileum and MLN after 6 months of infection were also significantly reduced in 1.0% Ca mice. These results suggest that Ca metabolism is an im portant modulator of M. paratuberculosis infection. (C) 1998 Published by E lsevier Science B.V. All rights reserved.