Studies on susceptibility to infection following ionizing radiation. I. The time of onset and duration of the endogenous bacteremias in mice.

Daily cultures of blood obtained from the tail were made on mice from the 7th day to the 17th or 22nd days after exposure to 550 r total body x-irradiation. Seven mice with negative blood cultures survived to the 27th day when they were sacrificed and found to have negative heart's blood cultures. Every mouse with bacteremia died. Heart's blood cultures post mortem always confirmed the bacteriological findings in the serial cultures. Most of the bacteremias occurred between the 7th and 15th days. The duration of the bacteremia varied with the microorganism which caused it. Pseudomonas bacteremia was always rapidly fatal. Those caused by Proteus and E. coli continued for a maximum of 72 and 48 hours. Of longest duration was bacteremia caused by Paracolobactrum which was tolerated for as long as 5 days.