Positive cerebrospinal fluid cultures after normal cell counts are contaminants

Previous literature on meningitis reports that cerebrospinal fluid (CSF) culture contaminants are threefold more common than true pathogens. Clinical follow-up of patients with CSF contaminants is costly, time-consuming, and potentially unnecessary. In this study, we hypothesized that, in immunocompetent Emergency Department (ED) patients with normal CSF cell counts and negative Gram stains, all positive bacterial cultures are contaminants and patient follow-up is unnecessary. We retrospectively reviewed 191 ED charts of patients with positive CSF cultures over 5 years. We abstracted lumbar puncture results, disposition, and follow-up activities, and determined monetary charges. There were 137 patients (72%) who met inclusion criteria with CSF white blood cells < or = 7 microL, negative Gram stain, and immunocompetence. Ninety-eight were discharged from the ED and 39 were admitted to the hospital for reasons other than meningitis. All 137 positive cultures were found to be contaminants, with coagulase-negative staphylococci found most commonly. Follow-up activities included telephone calls (49%), repeat ED visits (13%), repeat lumbar punctures (9%), unnecessary antibiotic treatment (6%), and hospitalizations (6%), generating $55,000 in charges. Follow-up may be unnecessary in ED patients with positive bacterial CSF cultures who were discharged from the ED, if their initial lumbar punctures were normal.