This study was conducted on 120 one day old broiler chicks which were divided into six groups, 20 birds each. Group 1 (control), group 2 (supplemented with probiotic), group 3 (challenged with Salmonella and receive no probiotic), group 4 (challenged with E coli and receive no probiotic), group 5 (challenged with Salmonella and supplemented with probiotic), group 6 (challenged with E coli and supplemented with probiotic). The experiment extended for 30 days starting from one-day-old chicks. Body weights, clinical symptoms, haematological analysis and postmortem lesions were demonstrated on 8 th , 15 th and 30 th day of the experiment. Also, histopathological studies of the intestinal mucosa, liver, spleen, thymus and bursa of Fabricius, as well as immunostaining of surface antigens (CD3A in the thymus and CD79A in the spleen and bursae of Fabricius), were also investigated. The current study revealed that supplementation of probiotic alone obviously improved weight gains as compared to the control group. Furthermore, probiotic supplementation decreased the colony forming a unit (CFU) of Salmonella enteritidis and E. coli (strain O2: H45) in the intestinal mucosa. Histopathologically, the intestinal mucosa showed an improvement which indicated by hyperplasia of the lining epithelium and abundance of goblet cells, but this local effect did not extend to other organs in the body that demonstrated mild to severe histopathological changes in challenged groups. The haematological analysis also verified that treatment with probiotics had no significant effect on most blood values (RBCs, WBCs and Hb). However, the differential leucocytic counts were significantly influenced by dietary treatment with probiotics which caused a highly significant decrease in lymphocyte percentage. In conclusion, probiotics obviously improved the growth performance and local immune response in the intestine, however no clear evidence of improvement of the general immune status of the experimental birds.

Yersinia enterocolitica is considered one of the most prevalent pathogens transmitted through milk and milk products. Therefore, we aimed to detect the prevalence of these bacteria in cheese and ice cream and study the influence of refrigeration and freezing on its growth patterns. A total of 80 samples of cheese and ice cream were collected from Assiut city, Egypt (40 samples each). The collected samples were examined for the isolation of Y. enterocolitica by the classical culture method and improved by the PCR technique. The incidence of Y. enterocolitica was 17.5 and 25.0 % in the examined cheese and ice cream samples by culture method, respectively, its prevalence in the tested cheese and ice cream samples basing on PCR were 7.5 and 15% since 42.8 and 60.0% of the isolated Y. enterocolotica were confirmed positive. Bio-typing and serotyping of the isolated strains revealed that 8 out of the confirmed strains were pathogenic ; Y. enterocolitica serotype O: 3 was the most prevalent strain, and all of the pathogenic strains carried the virulent ail gene. Nearly similar growth patterns of Y. enterocolitica were recorded during storage of cheese at 4 ± 2C and 30 ± 2ºC and, a significant difference was observed in the 3 rd week, the organism found to be survived for 18 weeks with a mean value of 7.4 ± 0.5 and 6.9 ± 0.16 log cfu/ g for cheese stored at 4 ± 2C and 30 ± 2C respectively. In the case of ice cream, there was a significant difference between the behavior of Y. enterocolitica during freezing storage at-6 ± 2C and-18± 2ºC in the 2 nd week, the mean value for the organism count on the 16 th week was 5.3 ± 0.26 and 5.6 ± 0.39 log cfu/ g, respectively.