الفهرس 
INTRODUCTION
PATHOGENESIS AND MODES OF MICROBIAL CONTAMINATION OF EGGSOnly 14 pages are availabe for public view
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Abstract
Bacterial contamination is happening on the surface of almost every egg of table eggs. Quality of eggs is depending on sanitation conditions of many factors including poultry farms, chicken nests and process of egg handling and storage.
The possibilities of contamination relies on the hygienic measures through which eggs and egg handlers pass, sanitary tracking to breeding farms, retails and ending by awareness of the consumers.
This study aimed to determine the bacterial contamination inside and outside the chicken eggs collected from different farms, variable groceries, markets and some roadside vendors in area of Assiut. Also samples from poultry farms environmental air and poultry feed.
This work also tested the different bacterial isolates response to different commonly used antimicrobial agents. The capability of penetration of some bacteria through egg shell specifically E.coli and Salmonella spp also has been also investigated.
E.coli isolates as the most predominated isolated bacteria were further screened for the virulence related genetic pattern through Multiplex Polymerase Chain Reaction (MPCR) test and Agarose Gel Electrophoresis.
This work has been executed for seventeen months through 2018 and 2019 using a total of 415 variable samples (350 table eggs collected from different sources) and 65 environmental samples; 40 poultry feed samples and 25 poultry houses environmental air samples.
E.coli, Salmonella spp, Proteus spp, Klebsiella spp, Pseudomonas spp and Staphylococcus spp. isolations were performed at the laboratories of Microbiology and Immunology Department, Faculty of Medicine, Assiut University using different laboratory and microbiological methods like bacterial culture on selective media, staining by Gram staining, motility and biochemical tests.
Results revealed 209(59.7%) of tested samples were positive for bacterial contamination. E. coli is the most prevalent strain 109(44.1%), Salmonella spp 22(8.9%), Proteus 13 (5.3%), Pseudomonas spp 6(2.4%) while Staphylococcus aureus was 38(15.4%) and Coagulase negative staph was 30(12.1 %).
The eggshell showed to be the more contaminated part of the table eggs while the contents (yolk and albumin) showed less contamination except for Salmonella spp isolates which was isolated more from the content. E. coli 28(13.4%), 16(7.7%), Salmonella spp 2(1.0%), 10(4.8%), Pseudomonas spp 3(1.4%), 1(0.5%), Proteus 7(3.3%), 1(0.5%) and Klebsiella spp 14(6.7%), 3(1.4 %) while Staphylococcus aureus 20(9.6%), 2(1.0%), Coagulase negative staphylococcus 13(6.2%), 3(1.4%) in the eggshell and the egg content respectively.
However, both eggshell and egg content together contamination rates were E. coli 65(21%), Salmonella spp 12(5.7%), Pseudomonas spp 2(1.0%), Proteus spp 5(2.4%), Klebsiella spp 12(5.8%), Staphylococcus aureus 16(7.7%) and Coagulase negative staphylococcus 14(6.7%),
Moreover, poultry feed showed bacterial contamination of E. coli, 10(40%) followed by 9(36%), 5(20%) and 1(4%) for Staphylococcus spp, Coagulase negative staph and Klebsiella respectively. While poultry house environmental air bacterial infection by Staphylococcus spp was 17(41.5%) and E.coli was 15(36.6%).
Isolated E.coli has shown Multi Drug Resistance to Amoxicillin 107(98.2%), Tetracycline 101(92.7%), Trimethoprim/sulphamethoxazole 99(90.8%) while the same isolates showed sensitivity to Imipenem 105(96.3%). Salmonella spp isolates showed sensitivity to Imipenem in 21(95.5%), and Trimethoprim/sulphamethoxazole resistance was in 20(90.9%).
In addition, Pseudomonas spp isolates showed resistance to tetracycline and Trimethoprim/sulphamethoxazole 4(66.7%) and highly sensitive to Imipenem 6(100%). Klebsiella spp showed sensitivity to Imipenem 26(89.7%) and resistance to tetracycline 28(96.6%). Proteus spp showed the same susceptibility pattern.
Staphylococcus aureus sensitivity to Imipenem was 38(100%) and Amikacin, Gentamicin 36(94.8%). Coagulase positive staphylococcus showed the same sensitivity in addition to Amoxicillin /clavulinic acids 30(100%).
Egg Penetration test revealed that bacterial pathogens especially E.coli and Salmonella spp have the capability to penetrate intact non-cracked eggs and grow grossly inside the egg content starting from fifth day of contamination at 20℃-25℃ through the multiple occurring pores in eggshell.
Moreover, E. coli isolates screen by Multiplex PCR test for the presence of 12 different identifying and virulent related genes showed that all tested strains were positive for uidA gene while Stx2 gene was detected in 26 isolates (23.9%) and astA gene in 29(26.6%).
The frequency of Stx1 gene was in 15 isolates (13.8%), invE genes was in 11 isolates (10.1%), elt gene was in 5 isolates (4.6%), estla gene was in 4 isolates (3.7%), eslb gene in 6 isolates (5.5%), aggR gene in 8 isolates (7.3%), escV gene in 18 isolates (16.5%), bfpB gene in 3 isolates (2.8%) and pic gene in 10 isolates (9.2%) were also detected in E. coli isolates.