Fungal DNA challenge in human STR typing of bone samples

The present study focuses on possible cross-reaction of fungal DNA with human STR primers that may affect subsequent forensic DNA analysis of forensic samples. Specificity of human STR markers namely HUMAMEL, HUMCSF1PO, D8S306, HUMTH01, HUMvWA, HUMFES/FPS, HUMF13A01, HUMDHFRP2, HUMFGA and HUMTPOX was tested using DNA of 24 different filamentous fungal isolates obtained from exhumed bone samples. The specificity of these ten STR markers for human DNA was demonstrated. Presence of non-human DNA in five bone samples analyzed did not alter scoring of detected alleles. Notably, amplification was inhibited in the presence of a high proportion of fungal DNA compared to human DNA (1000 ng: 1 ng) in DNA mixture experiments. The results of the present study underscore the importance of carefully analyzing the presence of non-human biological contaminants that may affect DNA typing of environmentally challenged forensic samples to avoid spurious data interpretation.