Objective: To detect and isolate the Gram-positive aerobic and facultative -anaerobic bacteria in hatching eggs. Design: Prospective longitudinal study. Animals: One hundered and twenty eggs from the broiler breeder stock and hatchery and 30 new-hatched chicks. Procedure: Bacteiological studies were done in five different developing stages: immediately after laying, before and after disinfecting, before moving from setter to hatcher and from new hatched chicks. Furthermore, two different samples were taken from the shell and the yolk of each egg. Eggs were washed with Nutrient-Broth Media, stored in 37°C for 24 hours and finally transferred to blood agar containing potassium telorite. Yolk samples were directly transferred to blood agar containing potassium telorite. This process was repeated similarly for those samples from yolk sac of IS-day-old embryos and newborn chicks. Statistical analysis: Exact fisher test. Results: The contamination rate of eggshells in different stages was 96.66%, 100%, 100% and 90%, respectively. Bacillus cereus, B. subtilis, B. polymixa and B. coagulans were isolated in 44.15%, 64.16%, 7.4% and 2.5% of cases, respectively. Staphylococcus aureus and S. saprophyticus were isolated from one yolk (3.3%) and tow yolk sacs (6.6%). Any bacteria was isolated from yolk sac of IS - day- old embryos. Clinical implications: The source of such contamination is mostly related to eggshells. In spite of routine managing programs in breeder stocks (such as selection, cleaning, and disinfection of eggs) it dose not effect to reduce Gram positive bacteria on egg shells and contamination of eggs in setter. Hence, yolk sac infection occurs and causes mortality in chicks.

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