Mannheimia haemolytica is a major cause of respiratory disease and mortality in lambs, responsible of significant economic losses in ovine flocks. The suspected diagnosis of mannheimiosis is generally based on clinical signs, characterized by lethargy, inappetence and fever along with histopathological aspects of progressive pneumonia and dark consolidation of lung parenchyma. However, further investigations are needed to confirm the infection, including isolation and biochemical identification of involved M. haemolytica strains but these methods are time-consuming. Assay based on PCR amplification of bacterial genome could be improve the sensitivity of the diagnostic protocol especially if the test is applied directly on the pulmonary tissues of infected animals. The aim of this study is to develop a novel PCR able to detect specific sequence of M. haemolytica in lung samples collected from lambs whit respiratory disease. Specific primers targeting a fragment of OmpA gene were designed and their specificity was evaluated using 8 strains of M. haemolytica and 2 of Pasteurella multocida. The limit of detection of the test is 0,067 picomol/µl of bacterial DNA, in agreement with previously described PCR protocols. One hundred samples of lungs showing gross lesions indicative of pneumonia, collected at the slaughterhouse from lambs belonging to 44 flocks of the Central Italy, were analysed by PCR and traditional microbiological test. The agreement between PCR and microbiology assays resulted fair (kappa=0,31), probably due to a different distribution of bacteria in lung parenchyma. Compared whit microbiology, PCR allowed to detect M. haemolytica strains in additional 15 tissue samples but failed to identify 17 samples positive only to microbial testing. Nevertheless, when applied in parallel testing, PCR resulted useful to increase the sensitivity of diagnosis, with a total of 38 flocks resulted positive to any of two test. These results suggest that the PCR test could be an efficient method for a rapid and early identification of mannheimiosis in lambs.
Molecular detection of Mannheimia haemolytica in lambs with respiratory disease
PROFETA, FRANCESCA;MARSILIO, Fulvio
2017-01-01
Abstract
Mannheimia haemolytica is a major cause of respiratory disease and mortality in lambs, responsible of significant economic losses in ovine flocks. The suspected diagnosis of mannheimiosis is generally based on clinical signs, characterized by lethargy, inappetence and fever along with histopathological aspects of progressive pneumonia and dark consolidation of lung parenchyma. However, further investigations are needed to confirm the infection, including isolation and biochemical identification of involved M. haemolytica strains but these methods are time-consuming. Assay based on PCR amplification of bacterial genome could be improve the sensitivity of the diagnostic protocol especially if the test is applied directly on the pulmonary tissues of infected animals. The aim of this study is to develop a novel PCR able to detect specific sequence of M. haemolytica in lung samples collected from lambs whit respiratory disease. Specific primers targeting a fragment of OmpA gene were designed and their specificity was evaluated using 8 strains of M. haemolytica and 2 of Pasteurella multocida. The limit of detection of the test is 0,067 picomol/µl of bacterial DNA, in agreement with previously described PCR protocols. One hundred samples of lungs showing gross lesions indicative of pneumonia, collected at the slaughterhouse from lambs belonging to 44 flocks of the Central Italy, were analysed by PCR and traditional microbiological test. The agreement between PCR and microbiology assays resulted fair (kappa=0,31), probably due to a different distribution of bacteria in lung parenchyma. Compared whit microbiology, PCR allowed to detect M. haemolytica strains in additional 15 tissue samples but failed to identify 17 samples positive only to microbial testing. Nevertheless, when applied in parallel testing, PCR resulted useful to increase the sensitivity of diagnosis, with a total of 38 flocks resulted positive to any of two test. These results suggest that the PCR test could be an efficient method for a rapid and early identification of mannheimiosis in lambs.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
