Persistence of salmonella enteritidis and typhimurium on hatching eggshells after 1, 6, or 24 hours

Authors: Harris, Caitlin; Bartenfeld Josselson, Lydia; BOURASSA, DIANNA - Auburn University; Buhr, Richard - Jeff

Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2019
Publication Date: 7/14/2019
Citation: Harris, C.E., Bartenfeld Jossel, L.N., Bourassa, D.V., Buhr, R.J. 2019. Persistence of salmonella enteritidis and typhimurium on hatching eggshells after 1, 6, or 24 hours. Poultry Science Association Meeting Abstract. 98(E-Suppl.1):97. p.42.

Interpretive Summary: none

Technical Abstract: Salmonellae are associated with eggshells, which predominantly become contaminated when contacted with infected feces from the cloaca or after lay. Our previous research has shown that holding inoculated eggs for 24 h depressed Salmonella recovery. The first objective of this study was to determine the impact of 3 holding times (1, 6, and 24 h) on Salmonella recovery from eggshells. The second objective was to determine if the presence of intact cuticle or egg contents impacted Salmonella recovery. Two experiments were performed with the following 4 treatments: control (no eggshell modification), chemically or mechanically altered cuticle, and eggshell without contents. On day 1, eggs were assigned to one of the 4 treatments (n=36 Exp 1, n=48 Exp 2). For the chemically altered cuticle treatment, eggs were submerged in 100% alcohol for 10 mins (Exp 1) or 30 mins (Exp 2). For the mechanically altered cuticle treatment, sandpaper was used to buff the cuticle off a 4.52 cm area on each egg. For the empty egg treatment, a hole was ground through the shell and the contents were removed. All eggs were then placed into an incubator (42C) for 16 h incubation time prior to inoculation. For Exp 1, eggs were inoculated with 10 µL of 107 S. Enteritidis and for Exp 2, half of the eggs were inoculated with 105 S. Enteritidis and the remaining half inoculated with 105 S. Typhimurium. Each treatment was then divided between the 3 holding times after which eggs were cracked, contents were discarded, and eggshells crushed into a centrifuge tube containing 30 mL of 1% buffered peptone water. For direct samples, two loops (20 µL) of eggshell rinsates were streaked onto Brilliant Green Sulfa agar containing 100 µg/mL nalidixic acid. Plates and eggshell rinsates were incubated for 24 h at 37C, plates recorded as positive or negative, and enriched plating was performed. Prevalence data was analyzed using Chi Square. Total direct counts had low prevalence (17% Exp 1; 27% Exp 2) while enriched samples had higher prevalence (84% Exp 1; 82% Exp 2). For both experiments, as holding time increased, recovery of Salmonella decreased for direct plates (1 h: 43 and 47%; 6 h: 6 and 25%; 24 h: 0 and 9%). The control and both cuticle treatments were statistically similar while shells with no contents had higher recovery of Salmonella compared to the controls for both experiments at 1 h (p=0.0002 and <0.0001) and Exp 2 at 6 h (p=0.001). For Exp 2, recovery of S. Enteritidis was lower than S. Typhimurium for direct plating (1 h: 31 vs 63%; 6 h: 6 vs 44%; 24 h: 0 vs 19%). In conclusion, increase in holding times of inoculated eggs prior to sampling reduced shell Salmonella recovery and removal of egg contents improved Salmonella recovery.