Summary auto-generated
This study compared three DNA-based molecular typing methods for Porphyromonas gingivalis, a bacterium strongly associated with severe periodontitis. Researchers analyzed 32 isolates from eight married couples using restriction endonuclease analysis (REA), ribotyping, and AP-PCR (polymerase chain reaction with arbitrary primers). All three methods showed broad agreement in their findings: isolates from spouses in six of eight couples were indistinguishable, while isolates from unrelated individuals showed distinct types. REA produced complex patterns with over 30 bands, making interpretation difficult. In contrast, ribotyping and AP-PCR generated simpler patterns with fewer bands, facilitating comparison. Minor discrepancies existed: REA detected subtle polymorphisms in some isolates that ribotyping and AP-PCR could not distinguish, while ribotyping occasionally detected variation that the other methods missed. All three methods proved reproducible and suitable for epidemiological transmission studies. The authors concluded that AP-PCR offered practical advantages, being less time-consuming than ribotyping and simpler than REA, while providing reproducible results within 24 hours from a single colony.
Key findings
- All three typing methods (REA, ribotyping, and AP-PCR) demonstrated that P. gingivalis isolates from spouses in six of eight couples were indistinguishable, supporting spousal transmission of this pathogen.
- AP-PCR and ribotyping produced simpler, more interpretable banding patterns (4-8 and 4-8 bands respectively) compared to REA (>30 bands), making them more practical for epidemiological studies.
- Minor polymorphisms detected by REA in certain isolates were not reflected in AP-PCR or ribotype differences, suggesting these variations are restricted to small genomic regions.
- AP-PCR proved most advantageous for routine typing due to rapid turnaround (less than 24 hours), ease of performance, reproducibility, and applicability to single colonies.
- All three methods correctly identified that isolates from unrelated individuals were always distinct, confirming the methods' discriminatory power for transmission studies.
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Abstract
Porphyromonas gingivalis is associated strongly with severe periodontitis, but little information is available on possible transmission routes of this species. This study evaluated three DNA-based molecular typing methods for use in epidemiological surveys of P. gingivalis. In total, 32 isolates from eight married couples were investigated by: (i) restriction endonuclease analysis (REA) of whole chromosomal DNA; (ii) hybridisation of DNA fragments with ribosomal DNA (ribotyping); and (iii) amplification of DNA by the polymerase chain reaction with arbitrary primers (AP-PCR). The data obtained with the three methods were in broad agreement: in six of the eight couples, the isolates from husband and wife were indistinguishable, but isolates from unrelated individuals showed distinct types with all three methods. For some isolates, minor differences in REA pattern were obtained which could not be correlated with differences in ribotype or AP-PCR type. Ribotyping showed differences between isolates from one individual, which were indistinguishable with the other two methods. The patterns obtained with ribotyping or AP-PCR were simple in comparison to the relatively complex REA patterns. Although all three methods were concordant, AP-PCR was found to be the least time-consuming method. The data support the suggestion that P. gingivalis can be transmitted between spouses.