Determination of bacterial aetiologic factor on tracheobronchial lavage in relation to clinical signs of bovine respiratory disease.

This study aimed to determine the occurrence of Mannheimiahaemolytica, Pasteurella multocida and Mycoplasma spp., in relation to clinical signs of respiratory disease. Tracheobronchial lavage samples were collected from 96 (healthy and unhealthy) cattle in the State of São Paulo, Brazil. Mycoplasma spp. (12.5 %) and Pasteurellamultocida (15.50 %) were the most prevalent species. Bacillus sp., Staphylococcus sp., Escherichia coli, Klebsiella oxytoca, Pseudomonas aeruginosa and Klebsiella pneumoniae were also isolated. Mollicutes (70.83 %), Mycoplasmabovis (2.94 %) and Mycoplasma dispar (38.23 %) were identified using conventional PCR. Submassive sound on acoustic percussion of the thorax was associated with the absence of Mollicutes (P=0.025). Whistling (P=0.076) and coarse crackle (P=0.046) were associated with the absence of Mycoplasma dispar. Clear sound on acoustic percussion of the thorax was associated with the absence of Mycoplasmabovis (P=0.007). Coughing was associated with the presence of Pasteurellamultocida [P=0.035; confidence interval (CI), 1.12-26.89], but its absence was associated with mucopurulent (P=0.0215; CI, 1.55-34.5) and mucoid nasal discharge (P=0.068; CI, 19-28.5), submassive sound (P=0.031; CI, 1.23-75.5), fine crackle (P=0.058; CI, 1.23-20.1) and coarse crackle (P=0.046; CI, 2.38-70.8). The high prevalence of Pasteurella multocida and Mycoplasma spp. in unhealthy calves increases the importance of these micro-organisms in the pathogenesis of respiratory diseases. This study increases the information about the role of Mycoplasma dispar in respiratory diseases. Differences in some species in relation to clinical signs can be applied as a presumptive diagnosis.