Avian pathogenic Escherichia coli (APEC) causes extraintestinal infections in birds, leading to an increase in the cost of poultry production. The ColV plasmid-linked genes iroN, ompT, hlyF, iss, and iutA have previously been suggested to be predictors of the virulence of APEC. In this research, we analyzed the frequencies of these genes in a Brazilian collection of E. coli isolated from birds with colibacillosis (APEC) and from apparently healthy birds (avian fecal [A(fecal)]), as well as from the litter of poultry houses of apparently healthy flocks (avian litter [A(litter)]). All the isolates that harbored ompT also harbored hlyF, so they were considered as one trait for statistical analysis. The relationship between in vivo virulence in 1-day-old chicks, expressed as a pathogenicity score, and the number of genes in each isolate showed that isolates with less than two of the four genes were rarely pathogenic, while most pathogenic isolates contained two or more genes. Nevertheless, about half of the nonpathogenic isolates also harbored two or more genes, in agreement with previous observations that commensal E. coli isolates from the birds' microbiota can serve as a reservoir of virulence genes. Thus, the pentaplex polymerase chain reaction can be used to indicate that a strain carrying none or only one gene would be nonpathogenic, but it cannot be used to indicate that a strain with two to four genes would be an APEC. Isolates allocated to phylogenetic group B2, which is frequently associated with extraintestinal infections, had the highest pathogenicity scores, while isolates allocated to group B1 had the lowest.

RESUMO.-[Genes associados à patogenicidade deEscherichia coli patogênica para aves (APEC) isoladas de frangos de corte com sintomatologia clínica respiratória.] Os mecanismos de virulência das amostras de Escherichia coli potencialmente patogênicas para aves (APEC) têm sido continuamente estudados e acredita-se ser multifatorial. Certas propriedades são associadas primariamente a amostras virulentas e vêm sendo identificadas em amostras de E. coli isoladas de aves. Neste estudo um total de 61 amostras de E. coli, isoladas de frangos de corte com problemas respiratórios, foram testadas através da Reação em Cadeia da Polimerase (PCR), para a presença dos genes responsáveis pela capacidade de adesão, fimbria P (papC) e fimbria F11 (felA), produção de colicinas (cvaC), presença de aerobactina (iutA), resistência sérica (iss), hemaglutinina temperatura sensível (tsh) e presença de dos antígenos capsulares K1 e K5 (kpsII). O gene iss foi detectado em 73,8%, tsh em 55,7%, iutA em 45,9%, felA em 39,3%, papC em 24,3%, cvaC em 23% e kpsII em 18%.

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The Infectious Bursal Disease (IBD) is a contagious viral disease that affects young chickens and may cause high morbidity and mortality. As the virus is very resistant to the environment, vaccination is required in case of high infection pressure. Due to variations in the virulence degree of the vaccines available to control IBD, this study aimed at evaluating the pathogenicity and immunogenicity of three types of vaccines. In total, 220 one-day-old specific pathogen free (SPF) chickens were immunized with recombinant, immune-complex and intermediate vaccines, or not vaccinated (55 birds per group) and challenged with IBD G11 strain on day 25. On days 25, 30, and 35, the Bursa of Fabricius (BF) were submitted to gross and histological examination, and serum samples were submitted to ELISA to determined anti-IBD antibody titers. On day 23, chickens were submitted to the test of hypersensitivity to phytohemagglutinin to evaluate the immunosuppressive effect of vaccines on the cell-mediated immunity. The results have indicated that the immune-complex vaccine induced the most severe BF lesions, whereas the recombinant vaccine preserved BF tissue and cell integrity. The three evaluated vaccines induced humoral immunity of similar intensity. The cellular reaction to phytohemagglutinin of the chickens immunized with recombinant and immune-complex vaccines was less severe compared with the unvaccinated chickens. In conclusion, these results indicate that the immune-complex vaccine was the most pathogenic and that all vaccines were effective in protecting SPF chickens against IBD.

(BF) were examined by conventional optical microscopy and digital images were acquired and processed using Matlab ® 6.5 software. The Artificial Neuronal Network (ANN) was generated using Neuroshell ® Classifier software and the optical and digital data were compared. The ANN was able to make a comparable classification of digital and optical scores. The use of ANN was able to classify correctly the majority of the follicles, reaching sensibility and specificity of 89% and 96%, respectively. When the follicles were scored and grouped in a binary fashion the sensibility increased to 90% and obtained the maximum value for the specificity of 92%. These results demonstrate that the use of digital image analysis and ANN is a useful tool for the pathological classification of the BF lymphoid depletion. In addition it provides objective results that allow measuring the dimension of the error in the diagnosis and classification therefore making comparison between databases feasible.

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Background: Avian Pathogenic Escherichia coli is the main agent of colibacillosis, a systemic disease that causes considerable economic losses to the poultry industry. In vivo experiments are used to measure the ability of E. coli to be pathogenic. Generally, these experiments have proposed different criteria for results interpretation and did not take into account the death time. The aim of this study was to propose a new methodology for the classification of E. coli pathogenicity by the establishment of a pathogenicity index based in the lethality, death time and the ability of the strain to cause colibacillosis lesions in challenged animals.Materials, Methods & Results: A total of 293 isolates of E. coli were randomly selected to this study. The strains were isolated from cellulitis lesions, broiler bedding material or respiratory diseases and were previously confirmed through biochemical profile. The bacterial isolates were kept frozen at -20°C. The strains were retrieved from stocks and cultured in brain-heart infusion broth overnight at 37°C to obtain a final concentration of 109 UFC/mL. A total of 2940 one-dayold chicks from commercial breeding hens were randomly assigned to groups containing 10 animals and each group was subcutaneously inoculated in the abdominal region with 0.1 mL of the standard inoculum solution containing each of the strains. A control group of 10 broilers were inoculated with 0.1 mL of brain-heart infusion broth by the same route. The chicks were kept for seven days. They were observed at intervals of 6, 12 and 24 h post-inoculation during the first days. From the second day on, the chicks were observed at intervals of 12 h. According to the death time and to the scores of each lesion (aerosaculitis, pericarditis, perihepatitis, peritonitis and cellulitis), a formula to determine the Individual Pathogenicity Index was established. A value of 10 was established as the maximum pathogenicity rate for an inoculated bird. From this rate, 5 points corresponded to scores for gross lesions present at necropsy. For each lesion present, it represents 1 point. The remaining 5 points corresponded to the death time. To obtain the death time value, an index of 1, corresponding to the maximum value assigned to a death on the first day, was divided by the number of days that the birds were evaluated, resulting in a value of 0.1428, which corresponded to a survival bonus factor. It was possible to classify E. coli strains into four pathogenicity groups according to the pathogenicity index: high pathogenicity (pathogenicity index ranging from 7 to 10), intermediate pathogenicity (pathogenicity index ranging from 4 to 6.99), low pathogenicity (pathogenicity index ranging from 1 to 3.99) and apathogenic (pathogenicity index ranging from 0 to 0.99). The analysis of the strains according to their origin revealed that isolates from broiler bedding material presented a lower pathogenicity index.Discussion: It is possible that the source of isolation implies in different results, depending on the criteria adopted. This data reinforces the importance of use a more accurate mathematical model to represents the biological phenomenon. In the study, all avian pathogenic Escherichia coli strains were classified based on a pathogenicity index and the concept of the death time represents an interesting parameter to measure the ability of the strain to promote acute and septicemic manifestation. The use of a support method for poultry veterinary diagnostic accompanying the fluctuation of the bacteria pathogenicity inside the farms may indicate a rational use of antimicrobial in poultry industry.