Abstract
BackgroundGenotypic variability in M. hyopneumoniae has been reported within and among herds. However, information regarding VNTR types within single lung lobes is lacking. The objective of his study was to analyse M. hyopneumoniae infections and their association with VNTR types and lung lesions at the lobe level. Lungs from 300 pigs from 10 farms experiencing an enzootic pneumonia outbreak were collected and scored. M. hyopneumoniae was detected by real-time PCR and genotyped by MLVA assay in all samples.ResultsThe results showed genotypic variability within single pigs and among lung lobes. At the lobe level, infection with one VNTR type (SN infection) was dominant. Lobes with lesion scores > 0 were associated with positive results for real-time PCR. At the lobe level, no relationship was observed between infections with more than one genotype (MX infections) and the proportion of Mycoplasma-like lesions. Lesion-free lobes presented a higher proportion of MX infections than lobes scored > 0. M. hyopneumoniae was detected more frequently in the right lobe of the lung (p < 0.05), with a similar distribution within lobes for SN and MX infections. The anatomic conformation of swine lungs led to a higher prevalence of infections in the right lobe. However, this study showed that this condition did not affect the distribution of infections with multiple VNTR types. Nevertheless, careful consideration of sample selection should be practised for M. hyopneumoniae genotype analyses, including lung lobes with no visible lesions.ConclusionThe results did not show a significant association between the number of detected genotypes and the severity of the lesions at the lung lobe level, but revealed the unexpected detection of M. hyopneumoniae genotypes in lesion-free lobes. These results imply that a representative sampling of all lobes may lead to an accurate identification of the VNTR-type distribution. Further studies including factors that can affect pathogenetic evolution of this bacterium could shed light on the complexity of the relationship between genotypes and the lung lesions magnitude.
Highlights
Genotypic variability in M. hyopneumoniae has been reported within and among herds
Two hundred sixty lung lobes were positive for M. hyopneumoniae by real
Performing genotyping at the lobe level allowed an assessment of the genotypic variability within individual lung lobes, as well as the exact correspondence between visible lesions and the Variable Number of (VNTRs) types that caused them
Summary
Genotypic variability in M. hyopneumoniae has been reported within and among herds. information regarding VNTR types within single lung lobes is lacking. Pneumonic lesions caused by M. hyopneumoniae are predominantly well delineated in the cranioventral areas of the lung, involving the apical, middle, and accessory lobes, and in severe cases, lesions can extend and involve the caudal lobes [20]. It has a small genome, Mycoplasma harbours several variable numbers of tandem repeat (VNTR) regions [13]. Multiple locus variable number tandem repeat analysis (MLVA) is the preferred technique to investigate VNTRs and has been applied in various studies to characterize M. hyopneumoniae [2, 3, 12, 22] based on its high discriminatory power.
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