Cross-contamination in the molecular detection of Bartonella from paraffin-embedded tissues

The genus Bartonella comprises a group of gram-negative, fastidious bacteria. Because of diagnostic limitations of culture and serologic testing, polymerase chain reaction (PCR) has become a powerful tool for the detection of Bartonella spp. in blood and tissue samples. However, because many wild and domestic animals harbor Bartonella spp., transfer of Bartonella DNA during sample collection or histologic processing could result in false-positive PCR test results. In this study, we describe evidence of Bartonella DNA dissemination and transfer in the necropsy room and during the subsequent processing of formalin-fixed paraffin-embedded tissues. Bartonella DNA was amplified from different areas of the necropsy room, from the liquid paraffin in the tissue processor, and from different parts of the microtome. Unless stringent procedures are established and followed to avoid cross-contamination, the molecular detection of Bartonella spp. from tissue samples obtained at necropsy or processed in a multispecies histopathology laboratory will not be reliable.