CSF Glucose Reduction Before Pleocytosis Documented by Serial Lumbar Punctures in Neonatal Group B Streptococcal Meningitis

To the Editors: Bacterial meningitis in neonates may present without cerebrospinal fluid (CSF) pleocytosis, particularly early in the disease.1 We report a case demonstrating, through serial lumbar punctures (LPs), that CSF glucose reduction preceded pleocytosis in neonatal group B Streptococcus (GBS) meningitis. A 17-day-old female presented with 2 hours of fever (38.1°C) and irritability. She was born at term via vaginal delivery; maternal GBS screening was negative. The infant appeared mildly ill without meningeal signs. Blood sampling preceded LP by 25 minutes; no feeding or dextrose was administered. Initial CSF findings showed: white blood cell count <1/μL (normal), red blood cell count <1/μL (nontraumatic), glucose 35 mg/dL and CSF/serum glucose ratio 0.40 (reduced). Despite a normal cell count, the reduced glucose in an ill-appearing neonate prompted empiric antibiotics. Blood culture became positive at 18 hours and CSF culture at 22 hours, both yielding GBS. Repeat LP at 48 hours revealed marked pleocytosis (white blood cell 223/μL, 85% neutrophils), with further glucose reduction (27 mg/dL, ratio 0.33) (Table 1). The infant completed 21 days of antibiotics with a normal neurodevelopmental outcome. TABLE 1. - Temporal Evolution of CSF Parameters Parameter Initial LP (Hour 0) Repeat LP (Hour 48) CSF WBC, /μL <1 (Normal) 223 (Pleocytosis) Neutrophils, % N/A 85 CSF RBC, /μL <1 15 CSF glucose, mg/dL 35 27 CSF/serum ratio 0.40 (Reduced) 0.33 CSF protein, mg/dL 100 186 Gram stain Negative GPC in chains Blood culture Positive (18 h), GBS — CSF culture Positive (22 h), GBS Negative (after antibiotic initiation) GPC indicates gram-positive cocci; LP, lumbar puncture; RBC, red blood cell; WBC, white blood cell. This case documents that CSF glucose reduction was present when pleocytosis had not yet developed. The nontraumatic initial tap (red blood cell <1/μL) confirms this was not an artifact. Pre-analytical rigor—short blood-to-LP interval and absence of dextrose administration—supports valid glucose interpretation.2 Why might glucose reduction precede pleocytosis? CSF glucose decreases rapidly through bacterial consumption and inflammatory effects on blood–brain barrier transport.3 Meanwhile, GBS possesses virulence factors, including C5a peptidase, which may partly contribute to delayed neutrophil recruitment.4 In our institutional experience, CSF/serum glucose ratio ≤0.4 has occasionally been observed in febrile infants undergoing LP, including cases later confirmed as bacterial meningitis. This observation carries clinical implications. Normal CSF cell count does not exclude bacterial meningitis in neonates evaluated very early. When CSF glucose is reduced despite a normal cell count, this discordance should raise suspicion for early bacterial meningitis. Continuing empiric antibiotics while awaiting cultures—typically positive within 24 hours—is prudent. Negative maternal GBS screening does not eliminate late-onset disease risk.5 CSF glucose reduction may precede pleocytosis in neonatal bacterial meningitis. When reduced CSF glucose is observed despite a normal cell count, clinicians should consider early bacterial meningitis and continue empiric therapy while awaiting culture confirmation.