Synergistic protective role of mirazid (Commiphora molmol) and ascorbic acid against tilmicosin-induced cardiotoxicity in mice.

Tilmicosin (TIL) is a long-acting macrolide antibiotic approved for the treatment of cattle with Bovine Respiratory Disease. However, overdose of TIL has been reported to induce cardiotoxicity. The purpose of our experiment was to evaluate the protective effects of Commiphora molmol (mirazid (MRZ); myrrh) and (or) ascorbic acid (AA) against TIL-induced cardiotoxicity in mice. MRZ and AA were orally administered using stomach gavage, either alone or in combination for 5 consecutive days, followed with a single TIL overdose. TIL overdose induced a significant increase in serum levels of cardiac damage biomarkers (AST, LDH, CK, CK-MB, and cTnT), as well as cardiac lipid peroxidation, but cardiac levels of antioxidant biomarkers (GSH, SOD, CAT, and TAC) were decreased. Both MRZ and AA tended to normalize the elevated serum levels of cardiac injury biomarkers. Furthermore, MRZ and AA reduced TIL-induced lipid peroxidation and oxidative stress parameters. MRZ and AA combined produced a synergistic cardioprotective effect. We conclude that myrrh and (or) vitamin C administration minimizes the toxic effects of TIL through their free-radical-scavenging and potent antioxidant activities.

Glycosylative inactivation of chalcomycin and tylosin by a clinically isolated Nocardia asteroides strain.

Studies on the susceptibility of pathogenic Nocardia to macrolide antibiotics, chalcomycin and tylosin, showed that most of the Nocardia species examined were highly resistant to both antibiotics, although N. nova was moderately susceptible. N. asteroides IFM 0339 converted these macrolides into inactive metabolites by glycosylation at 2'-OH or glycosylation and reduction of the 20-formyl group. The structures of the metabolites were determined from NMR and MS data to be 2'-[O-(beta-D-glucopyranosyl)]chalcomycin (2), 2'-[O-(beta-D-glucopyranosyl)]tylosin (5) and 20-dihydro-2'-[O-(beta-D-glucopyranosyl)]tylosin (4).

Effect of bentonite incorporated in a feed ration with tilmicosin in the prevention of induced Mycoplasma gallisepticum airsacculitis in broiler chickens.

A factorial arrangement of tilmicosin and bentonite was evaluated for efficacy in broiler chickens infected with Mycoplasma gallisepticum and correlated to tilmicosin recovery in a feed assay method. Tilmicosin at 300-500 g/ton prevented development of airsacculitis. The addition of 2% bentonite to the ration caused tilmicosin at 300 g/ton to be ineffective in controlling air-sac lesions, whereas 400 and 500 g/ton were moderately effective. Six percent bentonite rendered tilmicosin completely ineffective at all dose levels. There was a direct correlation between the percentage of bentonite in the feed rations, the percentage of the tilmicosin recovered in the assay procedure, and the increased incidence of air-sac lesions.