Polymerase chain reaction for the diagnosis of bovine genital campylobacteriosis Reação em cadeia da polimerase para o diagnóstico de campilobacteriose genital bovina

Bovine genital campylobacteriosis is a common venereal disease of cattle; the prevalence of this disease can be underestimated mostly because of the nature of the etiological agent, the microaerobic Campylobacter fetus subspecies venerealis. The purpose of the current study was to evaluate the utilization of polymerase chain reaction (PCR) in the diagnosis of genital campylobacteriosis in samples obtained from bull prepuce aspirate, cow cervical mucus, and abomasum contents of aborted fetuses, collected into enrichment medium. Five different DNA extraction protocols were tested: thermal extraction, lysis with proteinase K, lysis with guanidine isothiocyanate, lysis with DNAzol, and lysis with hexadecyltrimethylammonium bromide (CTAB). The specificity, sensitivity, and technical application of the PCR assay were also evaluated with clinical samples and compared to bacterial isolation by standard culture. DNA extraction by the CTAB protocol provided better results in PCR, and it was able to detect 63 colony-forming units per ml of C. fetus. Out of 277 clinical samples tested, 68 (24%) were positive for Campylobacter fetus using PCR, while only 8 (2.8%) of the samples were positive by bacterial isolation in solid medium, proving the superiority of the PCR technique when compared to the standard isolation method, and providing evidence for its usefulness as a better screening test in cattle for the diagnosis of bovine genital campylobacteriosis.<br>Campilobacteriose genital bovina é uma doença venérea comum em bovinos. A prevalência desta doença pode ser subestimada na maioria das vezes pela natureza microaeróbica do agente etiológico, Campylobacter fetus subspecies venerealis. O propósito do presente estudo foi avaliar a utilização da reação de polimerase em cadeia (PCR) no diagnóstico de campilobacteriose genital em amostras obtidas de aspirado prepucial de touros, muco cervical de vacas e conteúdo abomasal de fetos abortados, coletados em meio enriquecido. Cinco protocolos diferentes de extração de DNA foram testados: termo extração, lise com proteinase K, lise com guanidine isothiocyanate, lise com DNAzol e lise com hexadeciltrimetilamônio brometo (CTAB). A especificidade, sensibilidade e a aplicação da técnica da PCR foram também avaliadas com amostras clínicas e comparadas com bactérias isoladas por cultura padrão. DNA extraído pelo protocolo de CTAB demonstrou os melhores resultados na PCR, e foi capaz de detectar 63 unidades formadoras de colônias de C. fetus por ml de meio. Das 277 amostras clínicas testadas, 68 (24%) foram positivas para Campylobacter fetus pela PCR, enquanto 8 (2,8%) das amostras foram positivas por isolamento bacteriológico, provando a superioridade da técnica de PCR quando comparada com métodos padrão de isolamento, e fornecendo evidências de sua utilização como um teste de melhor projeção para diagnóstico em campilobacteriose genital bovina

Genetic homogeneity and phage susceptibility of ruminal strains of Streptococcus bovis isolated in Australia

The genetic homogeneity of 37 strains of ruminal streptococci was investigated by comparing DNA fragment profiles on agarose gels following restriction endonuclease digestion with Hae III, Cfo I and Msp I. Thirty strains were indistinguishable from Streptococcus bovis strains, 2B, H24 and AR3. The remaining three strains were similar but not identical to a ruminal strain of Strep. intermedius (AR36). In addition, the susceptibility of these strains to infection by five bacteriophages was examined. Three of the phages (φSb02, φSb03 and φSb04) were specific to the strain of Strep. bovis from which they were isolated, while phages 2BV and φSb01 infected one and two strains, respectively, in addition to their primary host. It was concluded that although Strep. bovis is relatively homogeneous genetically, broad host range phages appear to be uncommon with this bacterial species

An investigation into the possibility of bluetongue virus transmission by transfer of infected ovine embryos

Bluetongue (BT), a disease that affects mainly sheep, causes economic losses owing to not only its deleterious effects on animals but also its associated impact on the restriction of movement of livestock and livestock germplasm. The causative agent, bluetongue virus (BTV), can occur in the semen of rams and bulls at the time of peak viraemia and be transferred to a developing foetus. The risk of the transmission of BTV by bovine embryos is negligible if the embryos are washed according to the International Embryo Transfer Society (IETS) protocol. Two experiments were undertaken to determine whether this holds for ovine embryos that had been exposed to BTV. Firstly, the oestrus cycles of 12 ewes were synchronised and the 59 embryos that were obtained were exposed in vitro to BTV-2 and BTV-4 at a dilution of 1 x 102.88 and 1 x 103.5 respectively. In the second experiment, embryos were recovered from sheep at the peak of viraemia. A total of 96 embryos were collected from BTV-infected sheep 21 days after infection. In both experiments half the embryos were washed and treated with trypsin according to the IETS protocol while the remaining embryos were neither washed nor treated. All were tested for the presence of BTV using cell culture techniques. The virus was detected after three passages in BHK-21 cells only in one wash bath in the first experiment and two unwashed embryos exposed to BTV-4 at a titre of 1 x 103.5. No embryos or uterine flush fluids obtained from viraemic donors used in the second experiment were positive for BTV after the standard washing procedure had been followed. The washing procedure of the IETS protocol can thus clear sheep embryos infected with BTV either in vitro or in vivo