How might aspergillus turn up in the molecular analysis of a bone biopsy? A bone infection was evident in an X-ray and MRI following surgery to straighten a hammer-toe. The biopsy didn't grow so they sent the sample to the university for a molecular analy

Osteomyelitis. Usually a bone culture as well a bone biopsy is performed for a bone infection. Anything is possible as far a bacterial infections did your foot look clinically infected ie cellulitis and drainage?
Many possibilitis. Could have been a true infection, a false positive due to a superficial contaminant, or possibly even a lab error.
This . This is a loaded question. To get to the root of any infection, there often needs to be an "outbreak" where several cases can be tracked to a common cause. In individual cases, this can be much more difficult because there are so many variables. Aspergillus is a mold that is common in the environment. One source notes specifically the northern hemisphere in fall and winter. When something is in a lot of places, it is difficult to determine which source caused the infection. For surgical wound infections, there is a complex interplay between the environment, the patient's immune system, and the wound. For an infection to be established, you have to have adequate numbers of pathogens (infection-causing organisms). They then have to overwhelm the immune system or be protected from it. Often hammertoe correction will involve some form of hardware. Regardless of where the aspergillus came from, once it is on the hardware (either before or after insertion), it will create a layer, called biofilm, which protects it from the immune system. Any poor circulation related to the wound will further limit access to the immune system. Another possibility is that the aspergillus is a contaminant that is not causing the infection. Sometimes, we just don't know what the cause is.
Contaminant. It is most likely a contaminant. The pcr assay is so sensitive and even a spore picked up in the air or from contact would show up.
Aspergillus. As stated this is a mold that has a problem living in an anaerobic state. I am inclined to lean toward lab error as well.