Genomic variability of Mycoplasma hyopneumoniae within pig lung lobes

Abstract

Background Genotypic 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. Results The 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. Conclusion The 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.

Causes of Sow Mortality and Risks to Post-Mortem Findings in a Brazilian Intensive Swine Production System

“…These conditions can indicate that these lesions have a chronic aspect; due to this, two-thirds of the lungs were negative for the investigated pathogens. Even in acute infection, lungs can be PCR negative [ 51 ] for chronic lesion; this index is even higher since the infection could be cleared [ 52 , 53 ]. Despite the negative results, our data show that some pathogens could impact the females’ health.…”

The role of co-infections in M. hyopneumoniae outbreaks among heavy fattening pigs: a field study

“…Therefore, the timing of sampling could greatly affect the likelihood of detecting all genotypes hosted by a pig. However, these results should be interpreted with caution because although TBS are considered a very sensitive type of sample for intra vitam diagnosis [ 20 ], VNTR types are individually hosted in each lung lobe [ 17 ], and the ability of TBS to detect all VNTR types in each lung has never been assessed.…”

“…The relationship between the detection of specific strains of M. hyopneumoniae or the presence of multiple VNTR types and lung lesion scores is controversial [ 13 , 17 , 18 , 38 , 39 ]. In this study, pigs with a history of MX infection during the outbreak show more severe lung lesions.…”

“…These samples were genotyped after with MLVA. Briefly, the method consisted of four conventional PCR for the amplification of Locus 1, Locus 2, P97-RR1, and P97-RR2 genes in accordance with the scheme proposed by Charlebois et al [ 13 ] and Tonni et al [ 17 ]. The PCR were performed with an Applied Biosystems thermocycler (Thermo Fisher Scientific), and the PCR products were examined by capillary electrophoresis (QIAxcel; Qiagen, Hilden, Germany).…”

“…The impact of other co-infecting microorganisms on lung lesions has been hypothesized [ 10 ] and investigated by experimental infection [ 11 , 12 ], but studies performed under field conditions are lacking. The genomic variability of M. hyopneumoniae [ 13 – 17 ] and the resulting lung lesions [ 18 ] have been widely studied. However, little is known about the role of co-infections on M. hyopneumoniae genetic diversity and their differential effects on the resulting lung sequelae.…”