Introduction: The present study aimed to investigate the effect of Enterococcus faecium EF55 on chickens, as well as its influence on proliferative activity of epithelial intestinal cells after infection with Salmonella enterica serovar Enteritidis phage type 4 (SE PT4). Moreover, the length and area of duodenal and jejunal villi of the birds were examined.

Introduction: Avian pathogenic Escherichia coli (APEC) is a leading cause of extraintestinal infection and heavy economic losses. Imparting immunity after vaccination with live attenuated strain vaccination is an ideal strategy for infection control. This study considers an FtsK knockout mutant strain as a candidate. Material and Methods: An FtsK knockout mutant of APEC strain E058 was constructed and the pathogenicity of the mutant and wild-type strains was further evaluated in chickens. Results: The 50% lethal doses of each strain for one-day-old specific-pathogen-free (SPF) chickens challenged experimentally via trachea were 105.5 and 107.0 colony-forming units (CFU) respectively. Chickens challenged with the wild-type strain exhibited typical signs and lesions of avian colibacillosis, while those inoculated with the mutant strain showed mild pericarditis and pulmonary congestion. The growth rate of the FtsK mutant strain was much slower than the wild-type strain in the heart, spleen, liver, and lung of infected chickens. Conclusion: These results indicated that the APEC FtsK mutant can be attenuated for chickens, and that this mutant has the potential for the development of an APEC vaccine.

Domestic poultry is a natural reservoir of Campylobacter, the host–pathogen interaction being predominantly asymptomatic. This study investigated whether chickens remain asymptomatic partly because of lactic acid bacteria (LAB).

Introduction: The main problem in poultry farming is the difficulty in producing food of animal origin without using antibacterial agents. Because most antibacterial compounds are dispensed in water, some water supply systems can be contaminated by antibiotics which are then administered to the animals unintentionally. This can lead to unexpected increases in antibiotic residues in food of animal origin. The aim of the present study was to determine whether the constant exposure of chicken broilers to enrofloxacin affects the withdrawal time of a therapeutic doxycycline that is intentionally administered to the chickens.

This study was carried out on serum samples collected from broiler breeder chicken flocks vaccinated with avian influenza (AI) H5N1 inactivated vaccine. These flocks included 23 flocks aged 13 to 47 weeks reared in close houses in 7 sites; two vaccinated breeder flocks for HI antibody monitoring by 5 weeks interval samples and 8 flocks aged 41 weeks reared in different sites with identified females and males samples. The vaccine was used in a dose of 0.2 ml at 1 day in hatchery and revaccinated with 0.5 ml at age of 18 days, 19- 20 weeks and 40 weeks. Hemagglutination inhibition (HI) test was carried out against homologous antigen. The study pointed out that AI H5N1 inactivated vaccine under field application induced irregular and low HI titres following the 1st two doses ranged from log 2 0.0 to 4.15 with great variation between flocks, where samples with titre 0-2 ranged from 20 to 100%. The 3rd dose at 19-20 weeks was essential to elevate HI titres 3.25 to 7.44 with more homogenizes flock immunity and lower percentage of titres 0-2 ( 0-20 %) and as measured by HI test. Revaccination of layer flocks at 40 weeks (fourth dose) improves flock immunity facing stress of egg production as evaluated by HI (5.52 - 6.33) and lower negative percentage (5.5-11.7%). Monitoring of breeder flock every 5 weeks is essential to detect proper time of revaccination as each flock has its HI antibody curve. There was a difference in HI tit re rang log 2 0.33 to 1.2 between male and female chicks reared in the same house, but this variation not affecting flock mean. Birds at aged 41 weeks having titres < log2 3 (Seronegative) were protected when exposed to contact with infected flock as showed no clinical signs or change in HI titres after 12 days. In conclusion the usage of homologous inactivated H5N1 vaccine in 4 doses in layer flocks was of value in improving chicken immunity to AI H5N1 wild strain circulate in our field

The pathogenic effect of representative local isolates of Aeromonas organisms was studied on 1٠0 native breed chickens. At 2 weeks of age, one hundred chicks were grouped into four equal groups (1-4); 25 birds each; after collection of fecal from all groups, examined and proved to be free from Aeromonas species. All groups were subcutaneously (s.c) inoculated with 0.5 ml containing 9×105 cfu /bird. Group 1 of chickens was infected by A. hydrophila; while group 2 was infected with A. caviae. The third group was infected with A. sobria; while, chicks of Group 4 were kept as non infected control. Results were showed mild clinical signs in some birds in theform of alternative diarrhea. Post mortem lesions showed general congestion of all carcasses. In severely emaciated cases the lesions were confined to the intestine, which filled with watery fluid and distended with gas. Results of Aeromonas reisolation revealed that all collected weekly fecal swabs were positive. While, percentage of A. hydrophila and A. caviae was 100% out of all testedorgans, while isolation of A. sobria was 100%, 100% and 80% from liver, intestine and heart; respectively. Histopathological examination of infected chicken organs showing focal coaggulative necrosis in liver with mononuclear cells infiltration that varied in severity between groups as less severe in A. hydrophila (Gr.1) than A. caviae (Gr. 2), while A. sobria (Gr. 3) was markedly affected showing severe degenerated and dissociated hepatocytes. Intestinal changes were severe in group 3 than 2 while group 1 showing the mildest comparatively the changes was consist of necrosed mucosa, gland with leucocytic infiltration in lamina propria. Under thecondition of our study we can conclude that the used Aeromonas isolates from field diseased chickens were of mild pathogenicity to s.c. inoculated 12 days old Fayoumi chicks with long course affection.

Acute upper respiratory disease in chickens is a major cause of economic losses due to high mortality rates especially in poorly managed cases. Respiratory disease in poultry is initiated by variety of viruses, bacteria and fungi. The current study aims to investigate the prevalence of avian pathogenic E. coli (APEC), their proteases and other virulence genes in respiratory viral disease outbreaks in broiler chickens. Quantitative RT-PCR (qRT-PCR) was performed on samples from 25 farms with respiratory affections, APEC was isolated and virulence determinants in E. coli were investigated phenotypically and genotypically. E. coli was isolated from different flocks (100%, n=25). They were positive to Congo red binding (100%, n=25), iss gene (100%, n=25), iutA gene (92%, n= 23), tsh gene (24%, n=6), vat gene (20%, n=5). Presence of iss gene and CR binding proves that all isolates are APEC. Although the entire 25 APEC isolates carried more than one virulence gene; either 2 genes (n=17), 3 genes (n=7) and 4 genes (n=1), no effect of the number of genes harbored on the mortality rates in different flocks was observed. The presence of two serine proteases genes (tsh and vat) was confirmed in a total of 10 isolates (40% of the isolates) with positivity to tsh gene (24%) and vat gene (20%). qRT-PCR for detection of IBV-S1, AIV-H9, AIV-H5 and velogenic NDV-F genes revealed that 96% (n=24), 44% (n=11), 12% (n=3) and 4% (n=1) of 25 farms were positive to IBV, AIV-H9, velogenic NDV and AIV-H5, respectively. The results showed that among the 25 flocks, single viral infection was observed in 12 flocks (11 IBV and 1 AIV-H9), while mixed viral infections were detected in 13 flocks; IBV/AIV-H9 (n=9), IBV/velogenic NDV (n=3) and IBV/AIV-H9/AIV-H5 (n=1).The average mortality rate was the lowest in flocks infected with IBV, higher rates of mortality were observed in flocks infected with AIV-H9, velogenic NDV and AIV-H5. Flock age seems to affect the mortality rate in flocks infected with AIV-H9 where flocks aging 16:20, 21:25 and 26:30 days suffered from 2.38%, 8.13%, 11.48% average mortality rates, respectively.

The effect of 10 times (10x) overdose of enrofloxacin was studied in broiler chickens. One hundred and eighty chicks were classified in 3 equal groups. The first group received normal theurapeutic dose of enrofloxacin (1x) in drinking water for the first 5 consecutive days of age and repeated again at 24th -28th day of age. The second group received 10x (overdose) at the same ages. The third group was left non-medicated as a control group. Blood samples were taken on the 6th, 14th, 29th and 34th day of age for different laboratory tests. Enrofloxacin at 10x caused a decrease in the value of the following parameters: HI antibody titers to NDV vaccine at the 14th and the 34th day of age, serum albumin at the 10th day of age, hemoglobin at the 29th and the 34th day, lymphocytic count and IBDV ELISA titers at 29th day of age, uric acid at 29th day, phagocytic activity at 34th day, Lactobacillus spp. count in duodenum, feed conversion efficiency and body weight gain. The 10x (overdose) increased serum urea and creatinine at 29th day of age, serum AST and ALT at 29th and 34th day of age, and heterophilic count. Histopathological degeneration in liver, spleen, kidneys, bursa of Fabricius and thymus were demonstrated by 10x (overdose) of enrofloxacin. Challenge with vNDV caused 66.6% mortality in birds received the 10x (overdose) compared with 33.3% in the vaccinated non treated control group.

This study was done to investigate the prevalence of the Enterobacteriaceae in chickens and eggs. Isolation of forty four different bacterial isolates belonging to Enterobacteriaceae from chicken egg samples, cloacal swabs and swabs from Hatcheries’s floor, the isolates from commercial flock swabs were biochemically identified as E coli, P. mirabilis E Sakazakii and E .cloacae by incidence 22%, 55 %, 11% and 11 % respectively. The isolates from Layers and broilers breeder cloacal swabs were biochemically identified to be E. coli, P. mirabilis E. fergusonii and E .cloacae by incidence 20 %, 20 %, 20% and 40 % respectively. The isolates from commercial eggs were biochemically identified to be Pantoea Sp. , Kluyvera sp., E Sakazakii , E.aerogenes and E.harmanii by incidence 33.3% , 16.6% , 16.6% , 16.6% and 16.6 % respectively. The isolates from fertilized egg samples were biochemically identified as E Sakazakii , E. fergusonii , E.coli , E. Cloacae , Aeromonas ,S. Anatum and Prov. Alcolifaciens with a number of 1 ,1, 3, 3, 2, 2 and 1 , incidence 8% , 8% , 23% , 23% , 15% , 15% and 8 % respectively. The incidence of Enterobacteriaceae isolates from floor swabs of both primitive and automatic hatcheries was 20.8 % and these isolates were biochemically identified to be Pantoea spp., Citrokoserilama, k.pneumo. Ozaenae and E .cloacae with number 2, 1, 1 and 1 also its incidence were 40%, 20%, 20% and 20 % respectively. We found that the most common isolated bacterium from eggs either fertilized orcommercial table eggs in our study was E.coli although we could isolate other bacterial species as Enterobacter, Proteus species , Escherichia fergusonii; E. Sakazakii, Klebsiella sp., S. anatum, and Pseudomonas sp..In-vitro sensitivity test of the isolated strains to various chemotherapeutic agents revealed that all isolates were sensitive to Ciprofloxacin, Enrofloxacin, and Amoxicillin.

Four groups of one-day-old SPF chicks were inoculated with the four IBV variants at 1 day old to study the virulence of these isolates. The results at 2 weeks post infection (PI) revealed that all isolates were able to induce serological resposne postinfection, respiratory distress and depression. 20% and 100% mortalities were recorded with isolates 4 and 23; respectively. Assessment of pathogenicity index and pathotyping (at the end of observation period “2wk-PI”), categorized the 4 tested isoaltes (4, 16,18, 23) into three isoaltes of high virulence (4, 18 and 23), and one isolate of intermediate virulence (16). About 50% reduction in body weight was recorded with the four IBV isolates 2 wk PI. Kidney lesions were nephritis-nephrosis with urate deposition in ureters, while microscopic lesions were associated with increase in the amount of rough endoplasmic reticulum (RER). Tracheal lesions recorded as increase the amount of mucin, while microscopic lesions were edema of mucosa and inflammatory cells in the lamina propria. The regime of administering the infectious bronchitis (IB) live commercial H120 vaccine at 1 day old SPF chicks, and the heterologous challenge with four variants (serotypes) at 4 weeks of age, was found to be poorly effective in protecting the respiratory tract of SPF chickens with protection percentages of 8.1%, 55%, 10.5% and 12.6% corresponding to field isolates of IBV 4, 16, 18 and 23; respectively. Protection was measured by assessing ciliary activity of the tracheal epithelium following challenge. It is suggested that the use of the live IB-H120 vaccine will not always broaden the protection against challenge with IB multiple serotypes isolated from Egypt. Therefore it is necessary to develop a new IB vaccines, either locally prepared or imported to overcome any new IB serotype that were emerged, through modifying vaccination strategies to make them appropriate to the field situation.