A Mixture of Nucleosides and Nucleotides Increases Bone Marrow Cell and Peripheral Neutrophil Number in Mice Infected with Methicillin-Resistant Staphylococcus aureus

We studied the effects of a mixture of nucleosides and nucleotides on the peripheral neutrophil number and the proliferation of bone marrow cells in mice challenged with methicillin-resistant Staphylococcus aureus. BALB/c mice were fed a nucleotide-free 20% casein diet (control) or this diet supplemented with nucleosides and nucleotides orally (Expt. 1) or intraperitoneally (Expt. 2 and 3). On d 10, the mice were challenged intravenously with methicillin-resistant S. aureus (6.7×10 colony forming units/L). In Expt. 1 and 2, numbers of total and differential counts of blood leucocytes were counted on d 0 (before), 1, 3 and 5 after the infection. In Expt. 3, 30 min before killing, bromodeoxyuridine (20 mg/kg), an analogue of thymidine, was administered intraperitoneally and its incorporation in the DNA synthetic phase of bone marrow cells was determined at 0 h (before), 3, 6 and 24 h after the infection. Mice fed the supplemented diet had higher (P<0.05) leucocyte and neutrophil numbers on d 0 compared with the control group. The neutrophil numbers tended to be greater in the supplemented group at 1, 3 and 5 d after the infection. Intraperitoneal administration of nucleosides and nucleotides increased (P<0.05) neutrophil numbers before and after the infection. Twenty-four h after the infection, incorporation of bromodeoxyuridine into the DNA synthetic phase of bone marrow cells in the group administered nucleosides and nucleotides was higher (P<0.05) than in the control group. We conclude that, following methicillinresistant S. aureus injection, intraperitoneal administration of a nucleoside-nucleotide mixture may stimulate bone marrow cell proliferation and increase the peripheral blood neutrophil numbers. Oral administration may elicit weaker effects