Molecular detection of Yersinia pestis in dental pulp

Gilbert et al. (2004) report on the lack of Yersinia pestis DNA detection in 108 teeth collected in five northern Europe suspected plague sites, thus challenging our discoveries in three southern Europe sites (Drancourt et al., 1998; Raoult et al., 2000). The interpretation of these negative results is either the absence of Y. pestis in tested specimens or a failure to detect it. Particularities in the epidemiology of Black Death in medieval northern Europe including the absence of the suitable rat species in some countries led to a controversy regarding the aetiology of Black Death in these countries. It is possible that different microbes were responsible for epidemics during the Middle Ages but present work does not help to resolve this issue. We detected specific Y. pestis sequences in three different sites in southern Europe, thus clearly demonstrating that Y. pestis was involved in historical plague epidemics in southern countries (Drancourt et al., 1998; Raoult et al., 2000). Basically, our strategy was based on the use of dental pulp as the sample and specific Y. pestis primers for detection. The reason why we choose dental pulp is that it is a well vascularized soft tissue in contrast to bone or dentine (Drancourt et al., 1998). It is sterile in patients without bacteraemia (Potsch et al., 1992). It may be equivalent to a small blood sample. We were able to recover viable Coxiella burnetii after apparent cure from the dental pulp of experimentally infected animals (Aboudharam, 2001). That dental pulp is a suitable tissue on which to base molecular detection of microbial nucleic acid was demonstrated not only by our work on ancient plague (Drancourt et al., 1998; Raoult et al., 2000) but also in an experimental animal model (Aboudharam et al., 2000) and detection of specific RNA sequences in HIV-infected patients (Glick et al., 1989, 1991). In contrast, dentine has never been tested experimentally for this purpose. We doubt that it may be superior to bone as it is not a soft, well vascularized tissue. To use dentine and not the dental pulp makes the use of teeth a nonsense.