Background: Classical criteria differ when performing cerebrospinal fluid (CSF) analysis in infants younger than 90 days with fever without a source (FWS). Our objectives were to analyze the prevalence and microbiology of bacterial meningitis in this group and its prevalence in relation to clinical and laboratory risk factors.
Methods: This is a substudy of a prospective registry including all infants of this age with FWS seen between September 2003 and August 2013 in a Pediatric Emergency Department of a Tertiary Teaching Hospital.
Results: Lumbar puncture was performed in 639 (27.0%) of the 2362 infants with FWS seen, the rate being higher in not well-appearing infants [60.9% vs. 25.7%; odds ratio (OR), 4.49] and in those ≤21 days old (70.1% vs. 20.4%; OR, 9.14). Eleven infants were diagnosed with bacterial meningitis: 9 were ≤21 days old (prevalence 2.8% vs. 0.1%; OR, 30.42) and 5 were not well-appearing infants (5.7% vs. 0.2%; OR, 23.06). Bacteria isolated were Streptococcus agalactiae (3), Escherichia coli (3), Listeria monocytogenes (3), Streptococcus pneumoniae (1) and Neisseria meningitidis (1). None of the 1975 well-appearing infants >21 days old were diagnosed with bacterial meningitis, regardless of whether biomarkers were altered.
Conclusions: In infants younger than 90 days with FWS, performing CSF analysis for ruling out bacterial meningitis must be strongly considered in not well-appearing infants and in those ≤21 days old. The recommendation of systematically performing CSF analysis in well-appearing infants 22-90 days of age on the basis of analytical criteria alone must be reevaluated.