Criteria | Causal relationship |
---|---|
Putative pathogen genome is present in most cases of disease | Microbial nucleic acid should be found preferentially in diseased sites in combination with anatomic, histologic, chemical or clinical evidence of pathology and not in areas lacking the pathology |
Only diseased tissue should harbor putative pathogen genome | Fewer, or no, copy numbers of pathogen-associated nucleic acid sequences should occur in non-diseased host or tissue |
Disease resolution should be accompanied by a reduction in copy number of pathogen genome | Disease resolution perhaps due to effective clinical treatment should lead to undetectable or reduced pathogen-associated nucleic acid. Any relapse in disease should see an increase in copy number |
Microbial sequence may be detected before disease or may correlate with disease severity | A causal relationship can be more strongly inferred when pathogen-associated nucleic acid is present before disease onset and copy number correlates with disease severity |
The nature of the microbial organism associated by detection of its nucleic acid should be consistent with known biological characteristics of that group of organisms | When phenotypes such as pathology, microbial morphology and clinical features are predicted by sequence-based phylogeny the meaningfulness of the detected sequence can be enhanced |
Microbe-associated sequences detected in disease tissue should be corroborated at the cellular level | In situ hybridization of microbial sequences in an area of tissue pathology (or where microorganisms are thought to be located) should be attempted |
Molecular evidence should be reproducible | Any sequence-based evidence for microbial causation must be replicated |