Diagnosis
Tap the shunt and the spinal fluid; 20% will have normal studies (PubMed). That is because the fluid in the shunt is separate from the immune system.
For ventricular-atrial shunts, also check blood cultures.
Epidemiologic Risks
Having a shunt? (Review).
Microbiology
Staphylococcus, coagulase-negative (found in 37% of specimens), Staphylococcus aureus (18%), and Propionibacterium acnes (9%), the rest were a variety of gram-negative rods (PubMed). Holding the cultures for two weeks will increase the yield (PubMed).
If you grow a colon organism like an E. coli, the peritoneal end of the shunt has eroded into the bowel. I have seen it 2 or 3 times.
Empiric Therapy
Vancomycin and cefepime or meropenem.
Shunt removal is associated in one large series with the best outcome (PubMed).
Curious Cases
Relevant links to my Medscape blog
Last Update: 02/10/19.