[On the significance of endotoxin in experimental typhoid. I. Extraction of endotoxin from mutants of Salmonella enteritidis and the effect of the endotoxin on infection in mice caused by those strains].

Infection-enhancing effect of purified lipopolysaccharide (endotoxin) from S-type Salmonella enteritidis was clearly observed even when its very small doses were given to mice intraperitoneally together with low-virulent R-type S. enteritidis. This effect of endotoxin was detected to a comparable extent also after several days following infection, but thereafter reduced gradually.Lipopolysaccharide fractions extracted from various mutants of S. enteritidis and Proteus OXK also showed the property of enhancing the infection with low-virulent S. enteritidis. This infection-enhancing effect of endotoxin was not reduced at all by the previous administration of antiserum to mice. The acidhydrolysate of endotoxin also showed infection-enhancing effect.Mechanisms of this effect of endotoxin were studied by following the distribution of infecting32Plabeled bacteria and the changes of cells counts in peritoneal fluid. Although the phagocytic activity of peritoneal exudate cells was not affected, if any, by administration of endotoxin, the bactericidal activity of them was markedly reduced. A majority of the bacteria were not killed in the peritoneal cells of mice which received endotoxin, tnd gradually multiplied in them. Total counts of peritoneal exudate cells markedly decreased after administration of endotoxin, while no remarkable chages of their differential counts occured. It was concluded that endotoxin enhanced bacterial infection by reducing the mobilization of peritoneal exudate cells as well as damaging their bactericidal properties rather than by affecting their phagocytosis.