J Exp MedJ. Exp. MedThe Journal of Experimental Medicine0022-10071540-9538The Rockefeller University Press131633182136259ArticleSTUDIES ON SUSCEPTIBILITY TO INFECTION FOLLOWING IONIZING RADIATION II. ITS ESTIMATION BY ORAL INOCULATION AT DIFFERENT TIMES POST IRRADIATIONHammondCarolyn W.CollingMargaretCooperDorothy B.MillerC. PhillipFrom the Department of Medicine, The University of Chicago, Chicago1519549954114181511954Copyright © Copyright, 1954, by The Rockefeller Institute for Medical Research New YorkThis article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).

Mice were inoculated by mouth at different times (2 hours, 5 days, and 11 days) after a single exposure to 550 r total body x-irradiation. The inocula contained approximately 107 Pseudomonas aeruginosa which was found to be quite harmless for unirradiated mice. Comparison of the cumulative mortality curves and of the incidence of Pseudomonas bacteremia showed their susceptibility to infection by this route to be greatest on the 11th day, somewhat less on the 5th day post irradiation, and least of all directly after irradiation. Since damage to the intestinal mucosa has been found to be maximal within the first few hours after exposure to doses of x-irradiation in this range, it seems reasonable to conclude that the increased susceptibility is not due to increased permeability of the mucosa of the gut, but to impairment of the animal's natural defenses against infection.