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Abstract
BackgroundAlthough the pathogenic effect of members of the Mycobacterium tuberculosis complex in susceptible hosts is well known, differences in clinical signs and pathological findings observed in infected animals have been reported, likely due to a combination of host and pathogen-related factors. Here, we investigated whether Mycobacterium bovis strains belonging to different spoligotypes were associated with a higher risk of occurrence of visible/more severe lesions in target organs (lungs and/or lymph nodes) from infected animals. A large collection of 8889 samples belonging to cattle were classified depending on the presence/absence of tuberculosis-like lesions and its degree of severity. All samples were subjected to culture irrespective of the presence of lesions, and isolates retrieved were identified and subjected to spoligotyping. The association between the presence/severity of the lesions and the isolation of strains from a given spoligotype was assessed using non-parametric tests and Bayesian mixed multivariable logistic regression models that accounted for origin (region and herd) effects.ResultsResults suggested a difference in severity in lesioned samples depending on the strain’s spoligotype. An association between specific spoligotypes and presence of lesions was observed, with a higher risk of finding lesions in animals infected with strains with spoligotypes SB0120, SB0295 and SB1142 compared with SB0121, and in those coming from certain regions in Spain.ConclusionsOur results suggest that strains belonging to certain spoligotypes may be associated with a higher probability in the occurrence of gross/macroscopic lesions in infected cattle, although these observational findings should be confirmed in further studies that allow accounting for the effect of other possible confounders not considered here, and ultimately through experimental studies.
Highlights
The pathogenic effect of members of the Mycobacterium tuberculosis complex in susceptible hosts is well known, differences in clinical signs and pathological findings observed in infected animals have been reported, likely due to a combination of host and pathogen-related factors
Given that the virulence of a pathogen is typically related with its ability to spread [10], the existence of differences in the capacity of Mycobacterium tuberculosis complex (MTC) strains to cause clinical lesions in infected hosts could have implications in disease eradication given that it could be hypothesized that more virulent strains may be transmitted faster
The most common spoligotype retrieved from cattle samples in the collection was SB0121, the most prevalent in the Iberian Peninsula [21]
Summary
The pathogenic effect of members of the Mycobacterium tuberculosis complex in susceptible hosts is well known, differences in clinical signs and pathological findings observed in infected animals have been reported, likely due to a combination of host and pathogen-related factors. We investigated whether Mycobacterium bovis strains belonging to different spoligotypes were associated with a higher risk of occurrence of visible/more severe lesions in target organs (lungs and/or lymph nodes) from infected animals. Members of the MTC cause a granulomatous-caseousnecrotical lesion that mainly affects the lungs and regional lymph nodes but can extend to other organs such as liver, spleen, kidneys, mammary glands, pericardium, uterus and brain [3]. Their pathogenicity is mainly based on four aspects: (i) their ability to multiply inside the macrophages of the host, (ii) their resistance to. Given that the virulence of a pathogen is typically related with its ability to spread [10], the existence of differences in the capacity of MTC strains to cause clinical lesions in infected hosts could have implications in disease eradication given that it could be hypothesized that more virulent strains may be transmitted faster (though could be detected easier due to the induction of a stronger immune response in the host)
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