Detection and survival of Campylobacter in chicken eggs

Campylobacter jejuni, a food-borne human pathogen, is widespread in poultry; however, the sources of infection and modes of transmission of this organism on chicken farms are not well understood. The objective of this study was to determine if vertical transmission of C. jejuni occurs via eggs.

Using a temperature differential method, it was shown that Campylobacter had limited ability to penetrate the eggshell. When C. jejuni was directly inoculated into the egg yolk and the eggs were stored at 18 degrees C, the organism was able to survive for up to 14 days. However, viability of C. jejuni was dramatically shortened when injected into the albumen or the air sac. When freshly laid eggs from Campylobacter-inoculated specific pathogen-free (SPF) layers were tested, C. jejuni-contamination was detected in three of 65 pooled whole eggs (5-10 eggs in each pool) via culture and PCR. However, the organism was not detected from any of the 800 eggs (80 pools), collected from the same SPF flock, but kept at 18 degrees C for 7 days before testing. Likewise, Campylobacter was not recovered from any of 500 fresh eggs obtained from commercial broiler-breeder flocks that were actively shedding Campylobacter in faeces. Also, none of the 1000 eggs from broiler breeders obtained from a commercial hatchery were positive for Campylobacter.

These results suggest that vertical transmission of C. jejuni through the egg is probably a rare event and does not play a major role in the introduction of Campylobacter to chicken flocks.

Control of Campylobacter transmission to chicken flocks should focus on sources of infection that are not related to eggs.