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IS6110 homologs are present in multiple copies in mycobacteria other than tuberculosis-causing mycobacteria
T D McHugh1, L E Newport, S H Gillespie
1Department of Medical Microbiology, Royal Free Hospital School of Medicine, London, United Kingdom.
Abstract:
We have previously demonstrated homology between a 181-bp fragment of IS6110 and DNA from mycobacteria other than tuberculosis-causing mycobacteria (MOTT). Genomic DNA from 14 strains of MOTT was digested with PvuII and was hybridized with a probe derived from the 181-bp fragment and the INS1/INS2 international standard probe at high stringency. Multiple banding patterns were obtained from isolates of M. avium-M. intracellulare, M. fortuitum, M. kansasii, and M. malmoense. Differences in the banding patterns between and within species were obtained. This suggests that mycobacteria possess a family of IS3-like elements. The species of isolates suspected of being M. tuberculosis must be carefully determined before IS6110 restriction fragment length polymorphism analysis, and caution must be used in designing and evaluating diagnostic PCR tests based on this element.
Insights
IS6110 DNA sequences show homology with DNA from non-tuberculosis mycobacteria (MOTT). Restriction fragment length polymorphism analysis revealed diverse banding patterns, suggesting a family of IS3-like elements in mycobacteria.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The insertion sequence IS6110 is a key genetic element in Mycobacterium tuberculosis.
- Previous studies indicated homology between a fragment of IS6110 and DNA from mycobacteria other than tuberculosis (MOTT).
Purpose of the Study:
- To investigate the presence and diversity of IS6110-related sequences in various MOTT species.
- To assess the utility of IS6110 for molecular typing and diagnostics in non-tuberculous mycobacteria.
Main Methods:
- Genomic DNA extraction from 14 MOTT strains.
- Digestion of DNA with PvuII restriction enzyme.
- Hybridization with probes derived from IS6110 fragment and INS1/INS2 standard.
Main Results:
- Multiple distinct banding patterns were observed across MOTT species, including M. avium-M. intracellulare, M. fortuitum, M. kansasii, and M. malmoense.
- Significant variations in banding patterns were detected both between and within species.
- These findings suggest the existence of a family of IS3-like mobile genetic elements in mycobacteria.
Conclusions:
- IS6110-related sequences are present and diverse in MOTT, indicating a broader family of IS3-like elements in mycobacteria.
- Accurate species identification is crucial before employing IS6110-based restriction fragment length polymorphism (RFLP) analysis.
- Caution is advised when developing and validating PCR-based diagnostic tests targeting IS6110 in MOTT.