ABSTRACT Salmonella spp. remain among the most important agents of foodborne diseases worldwide. The importance of Salmonella spp. in public health is linked to their wide range of antimicrobial resistance and to their pathogenicity and virulence in both human and animal hosts. The aim of this study was to determine the antimicrobial resistance patterns for Salmonella serotypes isolated from poultry sources in Brazil and to detect virulence-associated genes and verify their association with specific serotypes. A total of 163 strains of Salmonella enterica isolated from poultry sources in Southern Brazil were selected, and each belonged to one of 11 different serotypes. They were tested against ten antibiotics and examined for the presence of 26 virulence-associated genes by PCR. S. Typhimurium, S. Bredeney, S. Schwarzengrund and S. Tennessee showed the highest overall resistance rates. Approximately 18% of Salmonella strains were classified as multidrug-resistant strains. Our results indicate associations between antimicrobial resistance and specific serotypes. Most of the investigated genes presented a high frequency and a regular distribution, regardless of the serotype. Eight genes are positively or negatively associated with at least one serotype. The observed associations between antimicrobial resistance and specific serotypes are useful in developing specific control and treatment measures for each serotype. Despite the virulence genes being evenly distributed among the serotypes, some of these genes are associated with specific serotypes, and sefA, sopEand lpfA were selected as possible markers of Salmonella serotypes.
ABSTRACT Fowl cholera is a contagious disease that results from infection by the bacterium Pasteurella multocida. This microorganism is extensively distributed among animal species, but little is known regarding it’s pathogenesis and specificity to various hosts. Many studies using pathogenicity evaluation methods are subjective and difficult to quantify because they are often only involved in the observation of the lethal capacity of the agent in experimental inoculation. Due to a lack of more consistent data, this study aimed to establish a classification model of P. multocida pathogenicity in mice using strains isolated from poultry and swine. A total of 94 strains of P. multocida isolated from clinical cases of FC and from lungs of swine were tested. A volume of 0.1 mL of bacterial suspension was obtained from the concentration of 106 CFU/mL and inoculated by an intraperitoneal route in five mice. The animals were observed every six hours over seven days. In addition to the mortality observed, the time of death and gross lesions were also analyzed. The Pathogenicity Indexes obtained showed significant differences (p<0.05) according to the origin of the strains. Likewise, the number of gross lesions and isolation percentages were also varied (p<0.05) among strains isolated from poultry and swine. From the observed ratios, the isolates were grouped into three pathogenicity classes: high, medium and low. This study proposed a consistent measurement and classification of P. multocida pathogenicity. The obtained results will be used to generate other adjusted models, as well as to form the basis for disease diagnosis.
ABSTRACT Although Pasteurella multocida is a member of the respiratory microbiota, under some circumstances, it is a primary agent of diseases , such as fowl cholera (FC), that cause significant economic losses. Experimental inoculations can be employed to evaluate the pathogenicity of strains, but the results are usually subjective and knowledge on the pathogenesis of this agent is still limited. The objective of this study was to establish a new methodology for classifying the pathogenicity of P. multocida by formulating a standard index. Strains isolated from FC cases and from swine with respiratory problems were selected. One hundred mL of a bacterial culture of each strain, containing 106 CFU, was inoculated in 10 one-day-old broilers. Mortality after inoculation, time of death (TD), and the presence of six macroscopic lesions were evaluated over a period of seven days post-inoculation (dpi). A Pathogenicity Index Per Bird (IPI), ranging 0 to 10, was calculated. Liver and heart fragments were collected to reisolate the bacteria. Blood was collected from the surviving birds, and an ELISA test was carried out to detect specific antibodies. The median of the pathogenicity indices, the number of lesions and the rate of bacteria reisolation were significantly different (p<0.05) among the origins of the isolates (p<0.05). The pathogenicity index developed in this study allows the classification of Pasteurella multocida pathogenicity and may be an alternative to the pathogenicity models currently used for screening.
ABSTRACT 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.
Brazilian poultry production is very efficient and demands maximum broiler performance. Therefore, digestive system pathologies have a relevant role. Considering it is difficult to obtain consistent information on intestinal morphometric analysis, this study aimed at establishing essential and clear criteria for the collection of intestinal segments for morphometric analysis. Fifteen 13-d-old broilers were sacrificed and three intestinal segments were collected per bird. Two 3-cm long sections were obtained from each of the intestinal segments. Samples were collected open or closed. The closed samples were transversely, hemicylindrically, or longitudinally sectioned. Samples were processed and stained with hematoxylin and eosin. The number of microscopic fields in each section was counted. Villi presenting the base clearly embedded in the submucosa, no damage or folds, and simple columnar epithelium at the tip were considered adequate for measurements. These villi were counted in each sample. The results shows that hemicylindrical sections presented the highest number of observation fields, with an average of 9.76 fields. Jejunum samples were among the three highest average villi counts, with 18.23 in longitudinal sections and 15.61 in hemicylindrical sections. The results of the present study indicate that hemicylindrical sectioning and jejunal samples were, respectively, the best sectioning method and the best intestinal segment for the morphometric analysis of the intestines of broilers.
Salmonellosis is an important disease with economic impact as it may affect animal performance and may result in foodborne disease in humans through the eggs and carcass contamination. Regarding the Salmonella control, it is possible to decrease its fecal excretion and the contamination of chicken carcasses by adding organic acids to the feed or drinking water at appropriate times. The aim of this study was to test a blend of organic acids and essential oils in broilers challenged with Salmonella Enteritidis (SE), and to verify the fecal excretion of Salmonella. Sixty broilers were placed in four groups. One group was the negative control. Another group was orally inoculated at 1 day-old with 10(5) CFU/mL of SE as a positive SE control. Two groups (T3 and T4) were orally inoculated at 1 day-old with 10(5) CFU/mL of SE and their feed was separately treated with 0.5 and 1% of organic acids and essential oils, respectively. To assess the fecal excretion of SE, cloacal swabs were collected from all birds at 2, 6, 13 and 20 days after inoculation. The T3 and T4 groups showed a reduction in fecal excretion of SE at 6 and 20 days after inoculation.
Campylobacter was investigated in cecal droppings, feces, and cloacal swabs of 22 flocks of 3 to 5 week-old broilers. Risk factors and the likelihood of the presence of this agent in these flocks were determined. Management practices, such as cleaning and disinfection, feeding, drinkers, and litter treatments, were assessed. Results were evaluated using Odds Ratio (OR) test, and their significance was tested by Fisher's test (p<0.05). A Campylobacter prevalence of 81.8% was found in the broiler flocks (18/22), and within positive flocks, it varied between 85 and 100%. Campylobacter incidence among sample types was homogenous, being 81.8% in cecal droppings, 80.9% in feces, and 80.4% in cloacal swabs (230). Flocks fed by automatic feeding systems presented higher incidence of Campylobacter as compared to those fed by tube feeders. Litter was reused in 63.6% of the farm, and, despite the lack of statistical significance, there was higher likelihood of Campylobacter incidence when litter was reused. Foot bath was not used in 45.5% of the flocks, whereas the use of foot bath associated to deficient lime management increased the number of positive flocks, although with no statiscal significance. The evaluated parameters were not significantly associated with Campylobacter colonization in the assessed broiler flocks.
Broiler chicks belonging to two poultry companies, A and B, with different breeders' vaccination programs were challenged with a very virulent strains of infectious bursal disease virus (vvIBDV), genotyped as G11. Birds were separated in four groups, two vaccinated at the first day of life and two unvaccinated. They were then challenged at the 1st, 4th, 7th, 10th, 13th, 16th, 19th and 22nd days. At every day of challenge, before and after the procedure, the following data were collected from each group: Bursa of Fabricius (BF) relative weight, BF diameter, BF for histologie examination, serum for measuring antibodies against IBDV through the ELISA and clinical evaluation of IBD. The results obtained have shown a non-significant drop in antibody level between the vaccinated and the unvaccinated groups. When analyzing the different results, it could be established that an ELISA titre of 3,4 log10 was the cutoff point between healthy and sick birds. Regression equations were built to determinate the best moment for vaccination and also the ELISA log titre birds what could present in a given age. Based on that, chicks from Company A should receive a vaccine against IBD from the 6th to 7th day of age, while the ones from Company B should get it between the 11th and the 12th day of age. Finally, the overall results suggest that the birds should not be vaccinated at one day old, and also that the breeders' different vaccination schemes resulted in progenies with different levels of maternal protection, and as a consequence the same vaccination plan should not be applied indiscriminately to broilers from different poultry companies.
Infectious Bursal Disease (IBD) is a chicken disease economically important for the poultry industry in function of the immune depression that it causes. Disease control is made with different vaccines and vaccination programs. In present work, the pathogenicity of 3 intermediate vaccines (I1, I2 and I3), 2 intermediate more pathogenic (IP1 and IP2) and 3 vaccines containing strong virus (F1, F2 and F3) was evaluated. Birds vaccinated with IP1, IP2, F1, F2 and F3 showed significantly lower bursa size in relation to control animals and animals vaccinated with I1, I2 and I3. On the other hand, vaccines I1 and I3 induced antibody titers higher than the control and lower than I2, IP1, IP2, F1, F2 and F3. Histological scores showed that vaccines I1, I2 and I3 induced similar injury degree, although I2 and I3 were not different from the control, whereas I1 was slightly different. Strong vaccines induced more pronounced lesions than the other tested vaccines. These findings suggest that strong vaccines are able to cause severe bursal injuries. However, bursometry and relative weight of the bursa of Fabricius were considered inadequate to evaluate vaccine pathogenicity. Moreover, strong vaccines induced higher antibody titers than the other vaccines, although some intermediate vaccines induced similar titers.