The efficiency of ionizing radiation in detoxifying the lethal determinant(s) of the lipopolysaccharide (LPS) of Salmonella typhimurium, S. enteritidis, and Escherichia coli in aqueous solution and associated with heat-killed S. typhimurium cells in suspension decreased with doses above 1 Mrad. The 50% end point of inactivation was more than 7.0 Mrad for heat-killed salmonellae and 4.8, 4.5, and 1.0 Mrad for the LPS of S. typhimurium, S. enteritidis, and E. coli, respectively. After exposure to 20 Mrad, S. typhimurium LPS retained a small portion of its lethal properties although the LD50 was much greater than 9.5 mg per 20-g mouse. However, at-184 C, no inactivation of the lethal determinant(s) occurred after exposure to as much as 20 Mrad. This demonstrated the significance of the indirect effect and the mobility and formation of free radicals. At 22 C, the optical density at 400 mA increased and the pH decreased with increasing radiation dose, but no qualitative changes were observed in the infrared spectrum. No change was observed in the pyrogenicity of S. typhimurium LPS; a slight decrease in antigenicity was revealed when 6 days, but not when 1 day, elapsed between vaccination and challenge in the mouse protection test. The results were interpreted as evidence of the existence of two or more lethal and antigenic determinants. The differential effect of radiation on these properties and on the pyrogenic component(s) probably are indicative of separate functional sites for lethal, antigenic, and pyrogenic activities.
The radiation resistance (D, in megarads) of six strains of Salmonella irradiated at 4C in brain heart infusion suspension ranged from 0.042 for S. enteritidis to 0.084 for S. thompson. The resistance values were 0.048 for S. typhimurium, strain SR-11, 0.060 for S. typhimurium, strain RIA, and S. newport, and 0.078 for S. heidelberg. The mutation frequency to tetracycline resistance of S. typhimurium, strain SR-11, increased between 0 and 0.05 Mrad and declined thereafter with increasing radiation dose. After 0.5-Mrad exposure, the mutation frequency was essentially the same as in control populations. The mutation frequency to streptomycin resistance of S. typhimurium, strain SR-11, decreased at doses greater than 0.05 Mrad and increased only slightly for the more radiation-resistant serotypes, S. typhimurium, strain RIA, S. thompson, and S. heidelberg. The average mutation frequency of the four Salmonella cultures tested was essentially unchanged (less than 1 log difference) between 0.05 and 0.5 Mrad, while the difference in reduction in viable numbers was 5 logs or greater. The evidence presented indicates that with the proper choice of processing parameters, the application of radiation pasteurization could drastically reduce the possibility of transmission of Salmonella by poultry and thereby decrease the public health hazards associated with this microorganism.
Growth of Salmonella typhimurium, strain RIA, in minimal broth supplemented with methionine, produced a population of cells that was more sensitive to 60Co irradiation than were those grown in brain heart infusion. The resistance values (D) were 0.056 and 0.066 Mrad, respectively. D was not significantly different when the bacteria were irradiated at 4 °C on fresh or frozen-thawed germ-free chicken, or on conventional chicken sterilized by autoclaving, or by exposure to 2 Mrad of ionizing radiation. It was generally higher when the cells were irradiated in the original growth medium than on chicken. D of five different strains of S. typhimurium irradiated at 4 °C on autoclaved chicken varied from 0.052 to 0.068 Mrad. The greatest increase in resistance was produced by decreasing the temperature during irradiation. S. typhimurium, RIA, attained a D value of 0.293 Mrad at −80 °C. The effect of the recovery media on survival is equivocal. In some instances nutrient and minimal agar seemed to provide slightly better recovery of strains SR-11 and RIA. Enrichment of complex media with yeast extract did not increase recovery. The results indicate that of those parameters studied, the most significant effects on resistance were due to the temperature during irradiation.
Summary An agent cytopathogenic in tissue cultures for cells of human origin was isolated from the feces of a 2 year old patient, R.S., with a 3 day febrile illness characterized by a skin eruption. Development of neutralizing and complement fixing antibodies reacting with the agent was demonstrated in the patient's convalescent serum. Preliminary serologic studies indicated that the agent isolated from patient R.S. and the group of cytopathogenic agents isolated from other patients with an epidemic exanthem illness were not related. The agent from R.S. characteristically induced a peculiar type of nuclear degeneration in roller cultures of human embryonic skin-muscle, foreskin, uterine and kidney tissues. Clinical features of the illness in patient R.S. suggest that the disease may have been roseola infantum.
Summary Single fecal specimens from 216 patients were examined for the presence of poliomyelitis viruses by means of the roller-tube tissue culture technique employing mostly human tissues. Twenty-five additional specimens had previously been found positive for virus by an alternate technique. Specimens from which no virus was obtained at first were re-examined by modified procedures permitting the use of large quantities of material as inocula. A comparison of the efficiency of the various procedures for isolation of these agents is given and the results correlated with the clinical diagnoses. Virus was recovered from 96% of patients diagnosed as paralytic poliomyelitis, thus attesting to the sensitivity of the procedures. In contrast, these agents were obtained from only 43% of subjects diagnosed as nonparalytic poliomyelitis. A number of unidentified viruses were also recovered. A comparison of the sensitivity of various human tissues in the detection of poliomyelitis virus is also presented along with similar data for monkey and human kidney tissues. Application of the techniques that have been described may be expected to result in a high incidence of virus recoveries from feces of patients with poliomyelitis. The antigenic type of each of the poliomyelitis viruses isolated has been determined. No difference in the distribution of viral types between paralytic and nonparalytic cases of the disease was observed.
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