02663nas a2200325   4500000000100000008004100001260001300042653001200055653003100067653003100098653002700129653002200156653001200178653002100190653001600211653000900227653002400236653003100260653002400291653001400315100002000329700002000349700001900369700002100388245010900409300001100518490000700529520178700536022001402323       2007                            d  c2007 Jun10aAnimals10aBacteriological Techniques10aChromatography, Thin Layer10aHorseradish Peroxidase10aHydrogen Peroxide10aleprosy10aLipid Metabolism10aMacrophages10aMice10aMicrobial Viability10aMycobacterium lepraemurium10aOxidation-Reduction10aVirulence1 aWek-Rodriguez K1 aSilva-Miranda M1 aArce-Paredes P1 aRojas-Espinosa O00aEffect of reactive oxygen intermediaries on the viability and infectivity of Mycobacterium lepraemurium.  a137-450 v883 a<p>Murine leprosy is a natural disease of the mouse, the most popular model animal used in biomedical research; the disease is caused by Mycobacterium lepraemurium (MLM), a successful parasite of macrophages. The aim of the study was to test the hypothesis that MLM survives within macrophages because it highly resists the toxic effects of the reactive oxygen intermediaries produced by these cells in response to infection by the microorganism. MLM cells were incubated in the presence of horseradish peroxidase (HRPO)-H(2)O(2)-halide for several periods of time. The peroxidative effect of this system was investigated by assessing the changes occurred in (a) lipid composition; (b) viability; and (c) infectivity of the microorganism. Changes in the lipid composition of peroxidated- vs. intact-MLM were analysed by thin layer chromatography. The effect of the peroxidative system on the viability and infectivity of MLM was measured by the alamar blue reduction assay and by its ability to produce an infection in the mouse, respectively. Peroxidation of MLM produced drastic changes in the lipid envelope of the microorganism, killed the bacteria and abolished their ability to produce an in vivo infection in the mouse. In vitro, MLM is highly susceptible to the noxious effects of the HRPO-H(2)O(2)-halide system. Although the lipid envelope of MLM might protect the microorganism from the peroxidative substances produced at 'physiological' concentrations in vivo, the success of MLM as a parasite of macrophages might rather obey for other reasons. The ability of MLM to enter macrophages without triggering these cells' oxidative response and the lack of granular MPO in mature macrophages might better explain its success as an intracellular parasite of these cells.</p>  a0959-9673