The Effect of Egg Shell Quality on Penetration by Various Salmonellae

Abstract

Eggs having specific gravity values of 1.070, 1.080 and 1.090 were challenged by 12 species of Salmonellae. Challenge was by dipping eggs for 3 minutes into solutions containing approximately 1 x 104 Salmonella organisms/ml. Egg temperature was 23° C. with the solution at 5° C. at the time of challenge after which the eggs were allowed to dry at room temperature, then stored at 30° C. for 24 hours prior to sampling for Salmonella penetration. Egg shells were sterilized with iodine, then opened and swab samples were incubated for 24 hours at 37° C. in tetrathionate and/or Selenite F broth, then streaked on MacConkey and SS Agar plates to determine presences of Salmonella organisms. Penetration into eggs of low shell quality (1.070) ranged from 14.3% by S. oranienburg to 82.1% by S. typhimurium and averaged 47.5% of all eggs challenged. Penetration averaged 21.4% of eggs of intermediate shell quality ranging from 7.5% for S. anatum and S. oranienburg to 48.7% of eggs for S. typhimurium. Average penetration was 10% of eggs of excellent shell quality ranging from 3.8% by S. anatum to 21.2% by S. typhimurium. Addition of 16 p.p.m. of iron to challenge solution increased penetration with five of six species tested.