Interference in diagnostic tests for brucellosis in cattle recently vaccinated against leptospirosis.

The aim of the current study was to verify if cattle vaccinated against leptospirosis may react in diagnostic tests for brucellosis. Sixty cows were divided into 5 groups, each comprising 12 animals. Four groups were given different vaccines against leptospirosis, while the control group received only saline. Two doses of vaccine were given, as recommended by the manufacturers. Serum samples were collected on the first day of immunization (day 0) and on postvaccination days 7, 14, 21, 28, 35, 42, 49, 56, 96, and 126. All the serum samples were tested for brucellosis and leptospirosis. Twenty animals were reactive at least once to the Rose Bengal test, but by day 96, no further reactions were elicited by this test. Twenty-six samples were reactive to the Rose Bengal test, but only 7 remained positive in confirmatory tests: 1 to the 2-mercaptoethanol test, 2 to the fluorescence polarization assay, and 6 to indirect enzyme-linked immunosorbent assays. None of the samples was reactive in the complement fixation test. None of the animals in the control group was reactive. A significant difference was found between the control group and the groups vaccinated against leptospirosis, according to Fisher exact test. However, the groups were found to respond independently of the vaccine brand. The results indicate that cattle vaccinated against leptospirosis may show reactivity on screening tests for brucellosis.

Toxinas e perfil protéico de amostras de Actinobacillus suis provenientes de plantéis suínos norte-americanos / Toxins and proteic profile of Actinobacillus suis samples from North American hog herds

Actinobacillus suis (A.suis) surgiu como uma grande ameaça aos plantéis suínos norte-americanos. Os sinais clínicos e as lesões são particularmente variáveis e podem lembrar aquelas causadas por outros organismos, como o Actinobacillus pleuropneumoniae (App), podendo ter como causa a similaridade na produção das toxinas ApxI e ApxII. Os objetivos do estudo foram confirmar a produção das toxinas ApxI e ApxII, investigar a produção de toxina geneticamente semelhante à Apx III e analisar as proteínas totais, verificando se existe similaridade entre os isolados provenientes de diferentes plantéis de suínos norte-americanos. Neste estudo, todas as cepas de A. suis foram positivas para os genes codificadores das toxinas ApxI e ApxII, usando o método de reação em cadeia de polimerase - multiplex (PCR-multiplex); e as proteínas totais de 70 amostras de A. suis, oriundos de diferentes plantéis suínos norte-americanos, foram analisadas por meio de eletroforese em gel de poliacrilaminda desnaturante (SDS-PAGE) e foram idênticas. A similaridade eletroforética observada entre as proteínas totais das bactérias analisadas indica a possibilidade de haver uma proteção cruzada a partir de uma provável vacina universal desenvolvida com esses antígenos para A. suis.

Actinobacillus suis (A. suis) has arisen as a great threat to the North American hog herds. The clinical symptoms and lesions are particularly variable and may resemble the same caused by other pathogenic organisms, such as Actinobacillus pleuropneumoniae (App), which can similarly lead to the production of the toxins ApxI and ApxII. This study aimed to confirm the production of the toxins ApxI and ApxII, as well as, to investigate the production of toxins that are genetically similar to ApxIII, and analyze total protein to verify whether there is any similarity among the isolated samples obtained from different North American hog herds. In this study, all the strains of A. suis were positive for the genes that codify the toxins ApxI and ApxII using the multiplex polymerase chain reaction (PCR-multiplex) method; and total protein from 70 samples of A. suis, obtained from different North American hog herds, were analyzed through denaturing polyacrylamide gel electrophoresis (SDS-PAGE), and were identical. The electrophoretic similarity observed among total protein of the analyzed bacteria indicates that there is the possibility of existing a cross protection in case of developing a probable universal vaccine with the antigens of A. suis.