Comparison between rinse and crush-and-rub sampling for aerobic bacteria recovery from broiler hatching eggs after sanitization

Authors: Spickler, Jessica; Buhr, Richard - Jeff; Cox Jr, Nelson; Bourassa, Dianna; Rigsby, Luanne

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2011
Publication Date: 7/1/2011
Citation: Spickler, J.L., Buhr, R.J., Cox Jr, N.A., Bourassa, D.V., Rigsby, L.L. 2011. Comparison between rinse and crush-and-rub sampling for aerobic bacteria recovery from broiler hatching eggs after sanitization. Poultry Science. 90:(7)1609-1615.

Interpretive Summary: The two most common methods for sampling hatching eggshells for aerobic bacteria are by eggshell rinse or crush-and-rub of the eggshell and underlying membranes. In a previous study, the recovery of aerobic bacteria from sanitized hatching eggs was similar for both the rinse and the subsequent crush-and-rub when conducted in a commercial hatchery cold room. The first experiment assessed three sanitizing chemicals to determine their efficacy against aerobic bacterial contamination on broiler hatching eggs. The chemicals examined were Hydrogen Peroxide (H2O2), Bio-Phene (Phenol), and Byotrol (Q4B, a compound chemical comprised of four quaternary ammoniums and one biguanide biocide moiety attached to a polymer core) for eggshell rinse and a subsequent crush-and-rub. Aerobic bacteria recovered (log10cfu/mL) from the eggshell rinse were highest and similar for No-treatment (4.0) and Water (3.7), lower for Phenol (3.2) and H2O2 (3.1), and lowest for Q4B (2.4). Crush-and-rub aerobic bacteria levels were similar for No-treatment (2.5) and Water (2.3), lower for Phenol (1.6), intermediate for H2O2 (1.2), and lowest for Q4B (0.9). A second experiment was designed to further examine the lower aerobic bacterial levels recovered by crush-and-rub (for previously rinsed eggs) than recovered in the initial eggshell rinse sample. Eggs were either rinsed and then crush-and-rubbed or only crush-and-rubbed without a prior rinse. Results confirmed a consistent significant decrease (1.5 log10cfu/mL) in bacteria levels between the initial rinse (4.4) and subsequent crush-and rub (2.9) for the same eggshell. For egg sampled by the crush-and-rub with no previous rinsing, the bacteria recovery level (3.9) was not significantly different from rinse levels. In summary, either the rinse or crush-and-rub sample methods can be used to recover similar levels of aerobic bacteria from broiler hatching eggs.

Technical Abstract: This study compared surface and deep eggshell aerobic bacteria recovered by rinse and crush-and-rub sampling methods for commercial hatching eggs after treatment with sanitizers. Eggs were arranged into 5 treatments consisting of No-treatment, Water, and three sanitizers. Sanitizers were Hydrogen Peroxide (H2O2), Phenol, and Q4B, (a compound chemical consisting of four quaternary ammonium and one biquanide moiety). Eggs were sprayed according to treatment and allowed to dry for 1 h before sampling. To collect samples for the eggshell rinse, each egg was massaged in a plastic bag with 20 mL saline. Eggshells were then aseptically opened and their contents discarded before being individually crushed into 50 mL centrifuge tubes containing 20 mL of saline. Aerobic bacteria were enumerated on Petrifilm™ after 48 h incubation at 37C. Aerobic bacteria recovered (log10cfu/mL) from the eggshell rinse were highest and similar for No-treatment (4.0) and Water (3.7), lower for Phenol (3.2) and H2O2 (3.1), and lowest for Q4B (2.4). Crush-and-rub aerobic bacteria levels were similar for No-treatment (2.5) and Water (2.3), lower for Phenol (1.6), intermediate for H2O2 (1.2), and lowest for Q4B (0.9). The overall correlation between the rinse and crush-and-rub sampling methods for individual egg aerobic bacteria counts was r = 0.71. The correlation within each treatment revealed the following r values: No-treatment 0.55, Water 0.72, H2O2 0.67, Phenol 0.73, and Q4B 0.38. A second experiment was designed to further examine the lower aerobic bacterial levels recovered by crush-and-rub (for previously rinsed eggs) than recovered in the initial eggshell rinse sample. Eggs were either rinsed and then crush-and-rubbed or only crush-and-rubbed without a prior rinse. Results confirmed a significant decrease (1.5 log10cfu/mL) in bacteria levels between the initial rinse (4.4) and subsequent crush-and rub (2.9) for the same eggshell. For the crush-and-rub eggs with no previous rinsing, the bacteria recovery level (3.9) was not significantly different from rinse levels. Therefore, either rinse or crush-and-rub sample methods can be used to recover similar levels of eggshell aerobic bacteria.