Background: In patients with CSF shunts, Propionibacterium species in thioglycollate broth may be a true infection or skin contaminant. We aimed to estimate the relative hazard of shunt externalization for infectious reasons after thioglycollate broth-only growth of Propionibacterium vs. coagulase-negative Staphylococcus (CoNS) vs. other microorganisms.
Methods: We performed a retrospective cohort study via manual chart review of all patients with microorganism growth in only thioglycollate broth from CSF culture at Duke University Clinical Microbiology Laboratory between January 1, 1996 and March 31, 2010. We estimated relative hazards of CSF shunt externalization following the first positive broth-only culture, censored at time of non-infectious shunt externalization, positive CSF culture with a different organism, death, 2 years after culture, or end of follow-up. Data were analyzed by Cox models, adjusted for age, co-morbidities, number of shunt manipulations, calendar time, and neurosurgeon.
Results: The cohort included 379 patients (median age 14.2 years, IQR 1.3-26.8) with 907 CSF broth-only cultures. At presentation, 304 (80%) patients had ≥1 clinical manifestation; 137 (36%) had ≥1 radiographic abnormality. Median CSF values were in the normal range; 14 (4%) patients had a repeat positive culture with the same organism in <90 days. 112 (30%) patients had their shunts externalized for an infectious reason within 2 years. Patients with Propionibacterium had lower point estimates for CSF shunt externalization than patients with CoNS (adjusted HR 0.68 [95% CI 0.35-1.30], P = 0.24) or other organisms (adjusted HR 0.66 [0.32-1.33], P = 0.24). Predictors of shunt externalization included younger age (adjusted HR 0.97 [0.96-0.99], P = 0.001), higher number of shunt manipulations (adjusted HR 1.16 [1.10-1.24, P <0.001), and neurosurgeon.
Conclusion: Patients with broth-only cultures for Propionibacterium did not undergo shunt externalization any more frequently than patients with likely contaminants. Later events requiring shunt externalization within 2 years were uncommon. Growth of Propionibacterium from CSF thioglycollate broth may often be a contaminant without major clinical consequences.
D. Williams, None
S. Costa, None
S. De Lurgio, None
R. Mckinney, None
G. Grant, None