Penetration of Serratia marcescens from the intestine into the organism of irradiated dogs

The role of bacterial infection in the fatal course of the radiation syndrome was investigated. Dogs were given a whole-body dose of 600-r x rays, and egress of bacteria from the intestine into the lymph was investigated. The presence of the test organism Serratia marcescens in the mesenteric lymph nodes, central lymph, peripheral blood, some organs, and the large intestine was investigated. Serratia could be found in mesenteric lymph nodes examined 24 hr and 5 days after irradiation. In the groups examined 8 and 15 days after irradiation bacteria were also present. The lymph was positive in half of the 8- day group and in 1/3 of the 15-day group. The controls and first 2 experimental groups were negative. The finding in the blood was similar to that in the lymph. Findings of bacteria in lymph removed from the thoracic duct in the 8-day group were twice as frequent as in the blood of the same period. The relatively low number of positive cultures from the intestine can be explained by unphysiological conditions existing there for any but the obligatory intestinal microorganisms. (TCO)