Propionebacterium acnes in cultures from ventriculo-peritoneal shunts: infection or contamination?

We have examined the accuracy of our present CSF sampling technique in 14 referred patients with suspect shunt dysfunction. The study was performed comparing culture results from shunt reservoir punctures and sham samples from skin tissue fluid close to the reservoirs. Propionebacterium acnes (P acnes) was found in five of fifteen cultures from reservoir punctures and in five of fifteen sham procedures. Positive cultures correlated in two cases. Thirteen of the fourteen patients included in the study were followed clinically and their symptoms disappeared without antibiotic or surgical treatment. One patient was treated surgically. We conclude that bacterial growth in cultures from shunt reservoirs in cases with P acnes should be interpreted with great caution, as our findings indicate that they may be skin contaminations.