Abstract
BackgroundAnimal mycobacterioses are regarded as a potential zoonotic risk and cause economical losses world wide. M. avium subsp. hominissuis is a slow-growing subspecies found in mycobacterial infected humans and pigs and therefore rapid and discriminatory typing methods are needed for epidemiological studies. The genetic similarity of M. avium subsp. hominissuis from human and porcine origins using two different typing methods have not been studied earlier. The objective of this study was to compare the IS1245 RFLP pattern and MIRU-VNTR typing to study the genetic relatedness of M. avium strains isolated from slaughter pigs and humans in Finland with regard to public health aspects.MethodsA novel PCR-based genotyping method, variable number tandem repeat (VNTR) typing of eight mycobacterial interspersed repetitive units (MIRUs), was evaluated for its ability to characterize Finnish Mycobacterium avium subsp. hominissuis strains isolated from pigs (n = 16) and humans (n = 13) and the results were compared with those obtained by the conventional IS1245 RFLP method.ResultsThe MIRU-VNTR results showed a discriminatory index (DI) of 0,92 and the IS1245 RFLP resulted in DI 0,98. The combined DI for both methods was 0,98. The MIRU-VNTR test has the advantages of being simple, reproducible, non-subjective, which makes it suitable for large-scale screening of M. avium strains.ConclusionsBoth typing methods demonstrated a high degree of similarity between the strains of human and porcine origin. The parallel application of the methods adds epidemiological value to the comparison of the strains and their origins. The present approach and results support the hypothesis that there is a common source of M. avium subsp. hominissuis infection for pigs and humans or alternatively one species may be the infective source to the other.
Highlights
Animal mycobacterioses are regarded as a potential zoonotic risk and cause economical losses world wide
The thirteen human clinical samples and the sixteen tissue specimens from nine different pigs with presumptive tuberculous lesions were investigated for the presence of mycobacteria
mycobacterial interspersed repetitive units (MIRUs)-variable number tandem repeat (VNTR) typing results The genetic diversity within the mycobacterial strains of human and porcine origin was studied by MIRU-VNTR typing
Summary
Animal mycobacterioses are regarded as a potential zoonotic risk and cause economical losses world wide. The objective of this study was to compare the IS1245 RFLP pattern and MIRU-VNTR typing to study the genetic relatedness of M. avium strains isolated from slaughter pigs and humans in Finland with regard to public health aspects. The bacteria belonging to the Mycobacterium avium complex are opportunistic microorganisms ubiquitously distributed in the environment. They transmit from the environment causing a majority of atypical human and animal mycobacterial infections. Bacteria belonging to the Mycobacterium avium complex, as well as other non-tuberculous mycobacteria (NTM), are infective to immunocompromized humans. In Finland during 1995 to 2004, a total of 3,961 NTM isolates were obtained from human specimens and M. avium was reported as the most common one as it was found in 1,360 (34%) of the 3,961 cases (Finnish National Health institute, KTL, annual reports, unpublished, in Finnish)
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