Factitious meningitis. Diagnostic error due to nonviable bacteria in commercial lumbar puncture trays.

A cluster of five false-positive cerebrospinal fluid (CSF) Gram stains led to an investigation of possible causes of specimen or smear contamination. Specimen tubes supplied in commercial lumbar puncture trays from the lot being used in the involved hospital were shown to contain nonviable bacteria, When filled with a test solution and processed in a manner similar to that used for processing CSF specimens, 10 of 12 tubes evaluated yielded Gram stains containing either Gram-negative rods, diplococci, or coccobacilli. Before this problem was recognized, the patient from whom the first false-positive smear was obtained was treated for bacterial meningitis. It is important to realize that microbial contamination of commercial CSF specimen tubes can result in findings simulating those of early bacterial meningitis.