Abstract
Mycoplasma hyopneumoniae, the primary pathogenic bacterium causing enzootic pneumonia, significantly affects worldwide swine production. The infection is usually persistent and bacterial identification and isolation of M. hyopneumoniae in clinical samples are challenging due to the fastidious requirements for its growth. Hence, new practical surveillance tools that improve or complement existing diagnostics on M. hyopneumoniae are desirable, especially in early infection. The objective of this study was to identify potential metabolite markers of early M. hyopneumoniae infection in pigs through metabolomics analysis. Samples obtained from pigs in a previous M. hyopneumoniae experimental infection were used in this study. Briefly, two pigs served as mock inoculated controls and ten pigs were intra-tracheally inoculated with M. hyopneumoniae. Sera, laryngeal swabs (LS), and tracheo-bronchial lavage fluid (TBLF) were collected from all pigs at 0, 2, 5, 9, 14, 21 and 28 days post-inoculation (dpi). Bronchial swabs (BS) were collected post-mortem at 28 dpi. Mycoplasma hyopneumoniae infection was confirmed by PCR in LS, TBLF and BS. Serum metabolites were profiled using high-resolution liquid chromatography–mass spectrometry (LC–MS) analysis. Metabolite markers were identified by structural analysis following multivariate analysis of LC–MS data. The results showed that M. hyopneumoniae infection time-dependently altered the serum levels of selective amino acids and fatty acids. α-Aminobutyric acid and long-chain fatty acids were markedly increased at 14 and 21 dpi in inoculated pigs (p < 0.05). These results indicated that M. hyopneumoniae infection caused systemic changes in host metabolism, warranting further studies to determine underlying biochemical and physiological mechanisms responsible for the observed changes.
Highlights
Mycoplasma hyopneumoniae (M. hyopneumoniae) is a major health risk in the porcine industry, causing enzootic pneumonia (EP), a chronic respiratory disease in growing pigs
Detection of M. hyopneumoniae genetic material Real-time PCR analysis of laryngeal swabs (LS), tracheo-bronchial lavage fluid (TBLF), and Bronchial swabs (BS) confirmed that mock inoculated control pigs were negative for M. hyopneumoniae throughout the study
M. hyopneumoniae DNA was detected in LS and TBLF of all pigs (100%) starting at 9 dpi (Figure 1A)
Summary
Mycoplasma hyopneumoniae (M. hyopneumoniae) is a major health risk in the porcine industry, causing enzootic pneumonia (EP), a chronic respiratory disease in growing pigs. Enzootic pneumoniae is often chronic, with a pattern of slow spreading and progression over the course of months, which usually results in herd morbidities that can reach up to 70–100% [1,2,3]. The incubation period of M. hyopneumoniae is difficult to predict under natural conditions as it may depend on the infectious dose, immune status of pigs, and presence of associated secondary. Chronicity is a prominent characteristic of mycoplasma infections. The ability of the bacteria to escape detection by adaptive immune surveillance mechanisms is associated with the challenges in early detection and prevention [8]. Because of low mortality associated with EP, post-mortem lung lesions are usually observed
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