Investigation of bacterial bioerosion phenomena in human bones

Bioerosive patterns in bone microstructure appear as microscopic focal destructions (MFD). Various hypotheses exist concerning the origin of MFD in bone microstructure. It is still discussed where exactly the decomposing bacteria originate from and the multiple factors that affect the bacterial bioerosion process. Formerly, it was hypothesised that the bacteria originate in the intestinal tract, which is strongly criticised nowadays. Therefore, this study aimed to investigate the origins of bone decomposing bacteria and found indications for the complex development of MFD.

120 thin-section specimens from six skeletal series were examined. The investigation focused on the MFD specific characteristics within the bone microstructure and possible explanations for the formation of the observed bioerosive patterns are discussed. The individuals of the studied skeletal series were buried in different ways, ranging from secondary burials in a cave (N_cave = 20) to cemetery interments (N_cemetery = 80) and chamber burials in a desert (N_desert = 14). While MFD were observed in all skeletal series, they were only detected in 37.5 % of the total thin sections. Moreover, there were differences in their abundance within the collections, ranging from low (N_{Lichtensteinhoehle} = 2; 10 % of the thin sections) to high (N_Inden/N_Goettingen = 14; 70 % of the thin sections).

In four of the skeletal series, less than half of the thin-section specimens examined were affected by microorganisms. However, only two skeletal series exhibited MFD in more than half of their thin sections (N_Inden/N_Goettingen = 14; 70 %). Several skeletal series contained thin sections with MFD predominantly located within osteons (N_all = 15), and several predominantly outside osteons (N_all = 4). Variations in abundance and location characteristics could be observed among the skeletal collections. Consequently, the formation of bacterial tunnelling is presumably not a singularly causal phenomenon. However, the results suggest that bacterial communities of exogenous origin cause the decomposition of a skeleton's bone microstructure.