Synergistic infection with murine cytomegalovirus and Pseudomonas aeruginosa in mice.

A previous report from this laboratory demonstrated that mice infected intraperitoneally with a 0--20% lethal inoculum of murine cytomegalovirus (CMV) exhibited markedly enhanced mortality rates (90%--100%) within 48 hr after an intravenous injection of a 0--20% lethal inoculum of Pseudomonas aeruginosa. The current study demonstrated that mice infected with murine CMV alone had high titers of virus in multiple organs over a 20-day period, whereas mice injected with P. aeruginosa alone had a self-limited infection confined to the kidney. In the combined murine CMV-P. aeruginosa infection, titers of virus in tissues were changed very little. In contrast, P. aeruginosa was recovered in high concentrations from multiple organs, a finding which demonstrated a progressive systemic infection closely resembling that produced by a 100% lethal inoculum of P. aeruginosa alone in normal mice. An increased mortality rate due to P. aeruginosa in murine CMV-infected mice was dependent on inoculation of live bacteria and could not be explained by enhanced susceptibility to endotoxin. These results indicate that murine CMF markedly enhanced the suceptibility of mice to infection with P. aeruginosa and suggest that the virus altered mechanisms of host resistance important in recovery from bacterial infections.