The aim of the present study was to analyze the possible bacterial contamination of fertile egg to establish the etiology of late embryo mortalities as well as its role in early chick mortalities due to yolk sac infection (YSI) named mushy chick disease. Many embryos die before hatching, particularly late in incubation, some chicks die at or shortly after hatching and in mostly up to 3 week. Forty fresh laid fertile eggs, forty infertile 19 to 21 day, forty piped dead in shell eggs were
taken, as well as liver and yolk sac samples from 60 dead chicks with signs and lesions of YSI at 1 to 14 days of age were cultured. One hundred and fifty three isolates were obtained from all samples. E. coli was the most common bacterium recovered from all samples. Other bacteria like K. pneumonia, Proteus vulgaris, Citrobacter freundii, C. jejuni, P. aeruginosa, S. aureus and Streptococcus spp were isolated from the examined samples. Fertile egg contamination at breeder
farm level was the minimal (13 isolates) followed by hatchery (30 and 49 isolates at the 19th and 21st days respectively) while 61 isolates were identified in dead chicks at 1-14 days-old. The rate of E. coli isolation (total 102 isolate) was increased with the time 5, 22, 33 and 42 out of fertile egg, at 19 and 21 days the hatchery and dead chicks; respectively; followed by S. aureus (17 isolates) and K. pneumonia (10 isolates) were obtained. Also, isolation of E. coli from egg shell in high rate from fertile and hatchery eggs indicates bad hygienic measures. This study pointed out
that the main etiologic agent of embryo mortality and YSI is E. coli in relation to other bacterial isolates that will be explored in the next study. Therefore, strict biosecurity measures must be adopted for hatching eggs, hatcheries and chicken farms with attention to use suitable effective disinfectants