Enrichment culture of CSF is of limited value in the diagnosis of neonatal meningitis

Neonatal meningitis is difficult to diagnose due to the subtle and nonspecific symptoms in neonates, and confirmation requires cerebrospinal fluid examination (CSF) [1]. Gram stain, culture of CSF directly onto agar plates, and broth enrichment culture are well established methods for diagnosing bacterial meningitis [2–5]. Other methods under evaluation include use of bacterial polymerase chain reaction combined with DNA sequencing [6]. The aim of CSF broth enrichment culture is to facilitate the isolation of damaged organisms and to recover those present in small numbers [7, 8]. The exact origin of enrichment culture is unknown [9]. Beijerinck and Winogradski are believed to be the first to recommend enrichment techniques [10]. We previously reported on the utility of various microbiology tests for the diagnosis of bacterial meningitis in the newborn [7]. We showed that enrichment cultures (inoculation of CSF into a brain-heart infusion broth incubated for 48 hrs) when performed on all lumbar puncture specimens are often falsely positive, because the prevalence of true bacterial meningitis is low in neonatal intensive care units and the test lacks specificity. We suggested that enrichment culture should be confined to settings where the prevalence of bacterial meningitis was higher, such as in samples with raised CSF white cell count (WCC), where organisms are seen on the Gram stain or where pathogens may be difficult to grow such as when babies have already received antibiotics. The aim of our current study was to assess the performance of enrichment culture when performed on CSF samples selected on the basis of a raised WCC of ≥30 /mm3