Concurrent murine cytomegalovirus and Klebsiella pneumoniae infections in germfree mice.

The effects of concurrent murine cytomegalovirus (MCMV) and Klebsiella pneumoniae infections were studied in germfree (GF) mice. The mice received sublethal doses, 5 x 10(5) pfu, of MCMV. K. pneumoniae was injected in doses of 40 to 100 cfu, which by itself killed 0-33% of GF mice. When K. pneumoniae was given to GF mice infected with MCMV, the mortality increased up to 100%, with distinct enhancement persisting until day 10 of the MCMV infection. The virus titer in various organs did not change after superinfection with K. pneumoniae, while the viable counts of K. pneumoniae in organs remained remarkably high until death, suggesting the cause of death to be severe generalized infection by the bacteria. When compared to specific pathogen-free (SPF) mice, GF mice were more susceptible to both MCMV and K. pneumoniae infection, had higher titers of the virus for longer periods in various organs, and showed extension in the duration of enhanced mortality by the bacteria. Histopathologically, the spleen and liver were found to be the most severely affected tissues, more so in GF than in SPF mice, with recovery from the changes being slower in the GF animals.