D values of Salmonella enteritidis isolates and quality attributes of shell eggs and liquid whole eggs treated with irradiation.

Irradiation sensitivity of five Salmonella enteritidis isolates inoculated either on the surface or inside of whole shell eggs were determined. The shell eggs were irradiated at doses of 0, 0.5, 1.0, and 1.5 kGy. A minimal dose of 0.5 kGy was sufficient to eliminate all the isolates from the surface of whole eggs; however, the same isolates were more resistant to irradiation when present inside the eggs. The ATCC 13076 isolate was significantly more sensitive to irradiation, with a D value of 0.32 kGy, than the other four isolates from animal origin. Irradiation D values of the latter ranged from 0.39 to 0.41 kGy. Liquid whole eggs were also inoculated (2.4 x 10(6) cells per milliliter) with two S. enteritidis isolates and were heat-treated at 50 C for 0, 20, 40, or 60 min followed by irradiation at 0, 0.25, 0.5, 0.75, or 1.0 kGy. The results indicate that mild heating prior to irradiation was ineffective in reducing the irradiation D values. However, on the basis of the D values obtained, an irradiation dose of 1.5 kGy should be sufficient to reduce Salmonella counts by approximately 4 log10 in both whole shell and liquid eggs. Results also indicate that color and thermal characteristics of the whole or liquid eggs were unaffected by a 1.5-kGy dose of irradiation.

[Biological effects of gamma rays on Salmonella gallinarum and their use in controlling fowl typhoid]. / Biologichni efekti na gamaluchite vurkhu Salmonella gallinarum i izpolzuvaneto im v borbata s tifusa po ptitsite.

The results are given of following up some biologic effects produced by gamma-rays on Salmonella gallinarum with a view of disclosing the possibilities of their use in the control of fowl typhoid. Used were strains of Salmonella gallinarum isolated from birds affected with acute typhoid. The possibility is stated of the detoxication of an endotoxin of Salmonella gallinarum parallel to the growing intensity of the gamma-rays (1 to 10 Mrad). It was found that the process of detoxication was better expressed in the irradiation of the bacterial cell in vivo. Rates of 20 Mrad were said to substantially modify the endotoxin, rendering it slightly toxic, it retaining its antigenic properties and haptene activity. The same modification could successfully be used as an allergen in the diagnosis of typhoid of birds when alive. It was also established that the use of sublethal rates of gamma-rays from 30 to 80 krad induced various morphologic and biochemical changes in Salmonella gallinarum. Of interest were likewise the studies of the R-strains and a histidine-dependent strain of Salmonella gallinarum which had retained their immunogenic properties.