Do Delays in Performing Lumbar Puncture After Administration of Antibiotics Alter the Results of CSF Cultures?

Abstract

Michael B, Menezes BF, Cunniffe J, et al.: Effect ofdelayed lumbar punctures on the diagnosis of acutebacterialmeningitis in adults. Emerg Med J 2010,27:433–438.Rating: †Of importance.Keywords Lumbar puncture · Acute bacterial meningitis ·Antibiotics · Cerebrospinal fluid culturesIntroduction: Bacterial meningitis is associated withsignificant morbidity and mortality despite the availabilityof antibiotics active against all common community-acquired pathogens. One of the major determinants of anadverse outcome is a delay in antibiotic administration,prompting the publication of national guidelines in theUnited States [1] and Britain [2] advocating the rapidadministration of empiric antibiotics shortly after presenta-tion. However, the need to institute treatment quickly mustbe balanced against the risk of performing a lumbarpuncture in a patient with a contraindication to thisprocedure. When lumbar puncture is delayed in patientswho first undergo neuroimaging, antibiotics may potentiallysterilize the cerebrospinal fluid (CSF), decreasing thelikelihood of making a microbiologic diagnosis.Aims: To determine whether national guidelines on themanagement of bacterial meningitis are being followed, andwhether delays in performing lumbar puncture after adminis-tration of antibiotics alters the results of CSF cultures.Methods: Patients ≥15 years of age hospitalized at a districtgeneral hospital in Northwest England with a dischargediagnosis of meningitis between January 2004 and Decem-ber 2006 were identified. Patients who did not have lumbarpuncture performed or whose CSF had less than 5 whiteblood cells (WBCs)/μL were excluded. Chart and electronicinformation system review were performed to identifybaseline clinical and microbiologic data. Contraindicationsto an immediate lumbar puncture were determined accordingto the British Infection Society meningitis guidelines [2].Patients were stratified by Meningitest criteria as to theprobability of bacterial or viral meningitis [ 3]. Patients with apositive CSF bacterial culture or CSF viral polymerase chainreaction (PCR) were considered to have confirmed bacterialor viral meningitis, respectively. Patients without a microbi-ologic diagnosis were classified as likely bacterial meningitisif the peripheral WBC was greater than 15,000 cells/ μLandthe CSF had all of the following characteristics: WBC greaterthan 1,700 cells/μL, proportion of neutrophils greater than80%, protein greater than 2.3 g/L, and CSF/serum glucoseratio less than 0.35. Patients who had negative microbio-logic evaluation and did not meet the above criteria forprobable bacterial meningitis were classified as likely viralmeningitis.Results: A total of 92 patients met inclusion criteria for thestudy. Bacterial meningitis was diagnosed in 24 (26.1%)cases, with confirmatory cultures in 16 (66.7%) cases.Neisseria meningitidis was cultured in 75% of the confirmedcases, followed by Streptococcus pneumoniae (18.8%) andListeria monocytogenes (6.3%). Eight (33.3%) cases lackedmicrobiologic confirmation but met Meningitest criteria forlikely bacterial meningitis. The remaining 68 (73.9%) caseswere classified as viral meningitis, with a single virologicallyconfirmed case of herpes simplex virus type 2 meningitis.