Nucleoside-nucleotide mixture and its components and response to methicillin-resistant Staphylococcus aureus infection in mice.

The effects of a nucleoside-nucleotide mixture and its individual components on response to methicillin-resistant Staphylococcus aureus (MRSA) strain 8985N were studied in mice. BALB/c mice were fed a nucleic-acid-free 20% casein diet and intraperitoneally administered a nucleoside-nucleotide mixture, its individual components (inosine, GMP2Na, uridine, thymidine, cytidine), or saline for 30 days. On the 10th day of this treatment, the mice were inoculated intravenously with the viable MRSA organisms. By the 20th day after inoculation, mice in the saline group showed 33% survival, whereas mice in the nucleoside-nucleotide mixture group showed 75% survival. The survival rates in the inosine (62%), GMP2Na (57%), uridine (54%), cytidine (50%), and thymidine (46%) groups were not significantly different. The survival rates of the individual-component groups tended to be higher than that of the saline group, but this was not statistically different. Furthermore, there was a greater reduction in viable organism recovery in the spleen and kidney of the surviving mice in the component groups than in the saline group. However, the survival rates in the individual-component groups did not exceed that of the nucleoside-nucleotide mixture group. This study suggests that intraperitoneal administration of a nucleoside-nucleotide mixture appears to be important in producing a high survival rate after challenge with MRSA. The effect cannot be achieved with the specific components of the mixture administered individually.