Bacterial Culture Confusion

Last week I was presented with a case of an older dog, who suddenly began to grow a lump on her head. The owner noted that the growth only took 24 hours to reach the size it was at the time of her appointment. On palpation, the mass felt fluid filled, and no puncture wounds were visible. As with all masses, I suggested a fine needle aspirate (FNA) and cytology. The FNA showed that the mass was indeed fluid filled, and it was a very hemorrhagic and appeared to have a purulent component. Due to the purulent component, I also submitted for anaerobic and aerobic culture. The fluid cytology report was very unhelpful in stating that this is a marked neutrophillic fluid with mixed inflammation.... I knew that already. The aerobic culture was negative, but the anaerobic culture left me scratching my head: few colonies of Wolinella spp. were grown on the culture media. For starters, I had never heard of Wolinella spp., and secondly, I had no idea of the origin of this bacteria. Quick and easy research showed me that this is a common pathogen found in mouths of dogs with periodontitis, but I know that this pooch did not bite his own head.... nor did he have any history of trauma or rough play with other dogs. So how do I explain this type of bacteria in this location... ??? Any ideas?

Culture Conscious

iCat