Prevalence and Predictors of Bacterial Meningitis in Young Infants With Fever Without a Source

Elena Martinez, MD; Santiago Mintegi, MD, PhD; Begoña Vilar, MD; Maria Jesus Martinez, MD; Amaia Lopez, MD; Estibaliz Catediano, MD; Borja Gomez, MD


Pediatr Infect Dis J. 2015;34(5):494-498. 

In This Article

Abstract and Introduction


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.


Infants younger than 90 days with fever without a source (FWS) have a greater risk of serious bacterial infections (SBIs) than did older infants, and this has traditionally meant a more interventionist approach in these patients, including hospital admission and performance of tests.[1,2] In recent decades, however, the prevalence of SBIs has decreased, thanks to better intrapartum antibiotic prophylaxis[3,4] and the early diagnosis of urinary malformations, as a result of prenatal ultrasound scanning.[5,6] Recent studies have also demonstrated a shift in the bacterial species involved. Listeria monocytogenes, classically considered as one of the main pathogens in young infants, has lost importance, and Streptococcus agalactiae and Escherichia coli are now being responsible for 75% of cases with a microbiological diagnosis of bacteremia in this age group.[7,8]

Regarding the current epidemiology of meningitis in this age group, recent publications have reported a significant decrease in the prevalence of L. monocytogenes as the causal agent of neonatal meningitis,[9] in parallel with the trend observed in bacteremia. Cerebrospinal fluid (CSF) analysis to rule out meningitis as the cause of the fever is performed more frequently in these pediatric patients given their milder clinical manifestations of invasive infections. Interestingly, 2 of the classical sets of risk criteria most used in practice differ regarding when to indicate this type of analysis. Specifically, although the Philadelphia criteria recommend the systematic use of lumbar puncture (LP) to classify patients as low risk,[10] Rochester criteria do not include this test.[11] Since the publication of these sets of criteria, the indications for CSF analysis have gradually changed, and currently, the decision is taken on a case-by-case basis, depending on the general condition of the patient, their age and the results of other tests. For instance, the American College of Emergency Physicians has recommended its use on a systematic basis only in children younger than 1 month.[1] Moreover, regardless of the guidelines adopted, there is a mixed adherence to any of these criteria in practice,[12,13] even in the specific subgroup of febrile neonates.[14]

With regard to the recommendation of performing CSF analysis based on blood test results alone, various authors have demonstrated that white blood cell count is not useful for identifying infants who are suitable candidates for this test.[15] On the other hand, new markers, such as C-reactive protein (CRP)[16,17] and more recently procalcitonin (PCT),[17–19] have proven to be more accurate for identifying young infants with SBIs, especially, in cases of invasive bacterial infection (IBI). Their use in the management of febrile infants could also modify the recommendations regarding the use of LP.

The objectives of this study were (a) to assess the prevalence of bacterial meningitis in infants younger than 90 days with FWS seen in a Pediatric Emergency Department (PED); (b) to identify the bacterial species involved and (c) to analyze this IBI in relation to clinical and laboratory findings classically considered to indicate high risk.