Abstract
Salmonellosis is an infection caused by specific or non specific serotypes of theSalmonella genus, responsible for losses in the poultry industry. Fowl typhoid, caused by S. Gallinarum (SG) is important because it causes elevated mortality in adult birds, leading to economic losses in the poultry industry. This study aimed at quantifying the number of viable SG cells in the liver, spleen, lung, cecum, and reproductive tract (ovary and testicles) of experimentally inoculated Japanese quails (Coturnix coturnix), as well as SG shedding in their feces. One hundred and two Japanese quails, with four months of age at the beginning of the experiment, were used. The birds were inoculated with three bacterial cultures containing different concentrations (6x104 CFU/0.1mL, 2x105 CFU/0.4mL, or 5x106 CFU/0.2mL) of SG resistant to nalidixic acid. On days 1, 4, 7, and 14 after the inoculation (dpi) individual cloacal swabs were collected from six birds per group, which were subsequently sacrificed for organ sampling. The swab samples were streaked directly on plates containing brilliant green agar and nalidixic acid (VBNal). Samples that were negative after 24h, were streaked again. The collected organs were individually macerated and transferred to buffered peptone water at 0.1%. The solutions were immediately diluted serially for CFU counting in VBNal. SG was successfully recovered from one quail, which was inoculated with 2x105 CFU/0.4mL, and from five quails of the group inoculated with 5x106 CFU/0.2mL inoculum. All of the analyzed cloacal swab samples were negative. Therefore, this study demonstrated it was difficult to isolate SG from the analyzed organs and that it was not possible to recover thepathogen in the cloacal swabs collected from inoculated quails. These results may be explained by the absence of flagella in SG, inducing weak intestinal immune response in the beginning of the infection and preventing its isolation in cloacal swab samples. The low positivity rate of the analyzed organs may be due to the immune status of the euthanized birds, since the SG dissemination in the animal organism occurs mostly close to death, which was observed in the birds found dead during the experiment.
Highlights
Salmonella Gallinarum is a pathogenic serotype of Salmonella specific of birds (Setta et al, 2012),and it is characterized by its capacity to grow in systemic locations (Chadfield et al, 2003)
The microbiological analyses showed that the cloacal swabs from all quails, as well as organ samples of the birds euthanized before the beginning of the experiment were negative for Salmonella spp
S. Gallinarum (SG) was recovered from 4.16% (1/24)of Group 1 birds (G1) birds and 20.83% (5/24) of group 2 (G2) and group 3 (G3) birds on 4 dpi and 7 dpi (G3), respectively, after selective enrichment inselenite-cystine broth (Table 1)
Summary
Salmonella Gallinarum is a pathogenic serotype of Salmonella specific of birds (Setta et al, 2012),and it is characterized by its capacity to grow in systemic locations (Chadfield et al, 2003). This serotype has been isolated from several poultry species, such as chickens, turkeys, pheasants, ducks, guinea fowl, and quails (Shivaprasad, 2000). (Bacci et al, 2012) and increasing severity of its infection in quails (Rocha e Silva et al, 2013). Pullorum are auxotrophic (Chappell et al, 2009)
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