Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/3/2008
Publication Date: 8/1/2008
Citation: Smith, D.P., Musgrove, M.T. 2008. Effect of blood spots on table egg albumen on Salmonella growth. Poultry Science. 87: 1659-1661 Interpretive Summary: Table eggs may occasionally contain small spots of blood in the egg white. These are removed during processing by candling so consumers rarely find them. The blood originates in the hen early in the formation process, right about the time the yolk is expelled from the ovary. Prior research has shown that some hens infected with pathogens, including Salmonella, have these organisms in the ovary. Egg white is typically a very difficult environment for bacteria to grow in, but extra blood may overcome those natural defenses, and bacteria may be present where those blood spots originate. This study examined whether blood spots did aid bacterial survival and growth in the egg white. In all three trials Salmonella did grow slightly better in the presence of blood when added to egg white. Since most blood spot eggs are rejected prior to sale there is little risk to consumers. More study is needed to determine whether blood in hatching eggs may aid bacterial pathogens being transferred from hens to eggs, and then chicks, since these eggs are not candled prior to incubation.
Technical Abstract: Presence of blood spots in eggs has been correlated with a higher rate of Salmonella enteritidis contamination. Therefore this study was conducted to determine whether Salmonella inoculated into egg albumen with naturally occurring blood spots would survive or grow. In each of three trials white-shell table eggs with blood spots were collected from a commercial egg processing plant after candling. In each trial eggs were broken out and approx. 4 mL of clear albumen (CLEAR) and 4 mL bloody albumen (BLOOD) from each of 10 eggs were placed in sterile test tubes and inoculated with a nalidixic acid-resistant Salmonella Typhimurium (ST). For inoculation, 0.1 mL of the ST suspension (containing 7.1, 7.7, or 7.0 log cfu/mL in Trials 1-3, respectively) was added to each tube. Tube contents were mixed and incubated at 250 C for 24 h. Immediately after inoculation (0 h) and again after 24 h, 0.1 ml from each tube was plated onto Brilliant Green-Sulfa agar with 200 ppm nalidixic acid and incubated at 370 C for 24 h. Results are reported as log cfu/mL albumen. No significant differences (P<0.05) in mean ST counts were found between CLEAR or BLOOD samples at 0 h (5.6 vs 5.8, respectively) indicating initial inoculation levels were consistent between treatments. After 24 h CLEAR samples were significantly lower than BLOOD samples for ST (6.5 vs 6.8, respectively). ST numbers increase slightly in albumen with or without blood, but slightly higher numbers are produced in albumen with blood spots. In this experiment, blood in the albumen of table eggs contributed to the survival and growth of Salmonella Typhimurium inoculated into egg albumen.