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Neonatal Bacterial Meningitis

By

Brenda L. Tesini

, MD, University of Rochester School of Medicine and Dentistry

Last full review/revision Jul 2020| Content last modified Jul 2020
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Neonatal bacterial meningitis is inflammation of the meninges due to bacterial invasion. Signs are those of sepsis, central nervous system irritation (eg, lethargy, seizures, vomiting, irritability [particularly paradoxical irritability], nuchal rigidity, a bulging or full fontanelle), and cranial nerve abnormalities. Diagnosis is by lumbar puncture. Treatment is with antibiotics.

Neonatal bacterial meningitis occurs in 2/10,000 full-term and 2/1,000 low-birth-weight (LBW) neonates, with a male predominance. It occurs in about 15% of neonates with sepsis and occasionally occurs in isolation.

Etiology of Neonatal Bacterial Meningitis

The predominant pathogens are

Other reported pathogens include enterococci Enterococcal Infections Enterococci are gram-positive, facultative anaerobic organisms. Enterococcus faecalis and E. faecium cause a variety of infections, including endocarditis, urinary tract infections, prostatitis... read more , nonenterococcal group D streptococci, alpha-hemolytic streptococci Streptococcal Infections Streptococci are gram-positive aerobic organisms that cause many disorders, including pharyngitis, pneumonia, wound and skin infections, sepsis, and endocarditis. Symptoms vary with the organ... read more Streptococcal Infections , Staphylococcus aureus Staphylococcal Infections Staphylococci are gram-positive aerobic organisms. Staphylococcus aureus is the most pathogenic; it typically causes skin infections and sometimes pneumonia, endocarditis, and osteomyelitis... read more Staphylococcal Infections , coagulase-negative staphylococci Staphylococcal Infections Staphylococci are gram-positive aerobic organisms. Staphylococcus aureus is the most pathogenic; it typically causes skin infections and sometimes pneumonia, endocarditis, and osteomyelitis... read more Staphylococcal Infections , gram-negative enteric organisms (eg, Klebsiella Klebsiella, Enterobacter, and Serratia Infections The gram-negative bacteria Klebsiella, Enterobacter, and Serratia are closely related normal intestinal flora that rarely cause disease in normal hosts. Diagnosis is by culture. Treatment is... read more species, Enterobacter Klebsiella, Enterobacter, and Serratia Infections The gram-negative bacteria Klebsiella, Enterobacter, and Serratia are closely related normal intestinal flora that rarely cause disease in normal hosts. Diagnosis is by culture. Treatment is... read more species, Citrobacter diversus), Haemophilus influenzae Haemophilus Infections The gram-negative bacteria Haemophilus species cause numerous mild and serious infections, including bacteremia, meningitis, pneumonia, sinusitis, otitis media, cellulitis, and epiglottitis... read more , Neisseria meningitidis Meningococcal Diseases Meningococci (Neisseria meningitidis) are gram-negative cocci that cause meningitis and meningococcemia. Symptoms, usually severe, include headache, nausea, vomiting, photophobia, lethargy,... read more Meningococcal Diseases , and Streptococcus pneumoniae Streptococcal Infections Streptococci are gram-positive aerobic organisms that cause many disorders, including pharyngitis, pneumonia, wound and skin infections, sepsis, and endocarditis. Symptoms vary with the organ... read more Streptococcal Infections .

Neonatal bacterial meningitis most frequently results from the bacteremia that occurs with neonatal sepsis Neonatal Sepsis Neonatal sepsis is invasive infection, usually bacterial, occurring during the neonatal period. Signs are multiple, nonspecific, and include diminished spontaneous activity, less vigorous sucking... read more ; the higher the colony count in the blood culture, the higher the risk of meningitis. Neonatal bacterial meningitis may also result from scalp lesions, particularly when developmental defects lead to communication between the skin surface and the subarachnoid space, which predisposes to thrombophlebitis of the diploic veins. Rarely, there is direct extension to the central nervous system (CNS) from a contiguous otic focus (eg, otitis media).

Symptoms and Signs of Neonatal Bacterial Meningitis

Frequently, only those findings typical of neonatal sepsis (eg, temperature instability, respiratory distress, jaundice, apnea) are manifest. CNS signs (eg, lethargy, seizures [particularly focal], vomiting, irritability) more specifically suggest neonatal bacterial meningitis. So-called paradoxical irritability, in which cuddling and consoling by a parent irritates rather than comforts the neonate (because movement of inflamed meninges is painful), is more specific for the diagnosis. A bulging or full fontanelle occurs in about 25% and nuchal rigidity in only 15%. The younger the patient, the less common are these findings. Cranial nerve abnormalities (particularly those involving the 3rd, 6th, and 7th nerves) may also be present.

Meningitis due to group B streptococcus (GBS meningitis) may occur in the first week of life, accompanying early-onset neonatal sepsis and frequently manifesting initially as a systemic illness with prominent respiratory signs. Often, however, GBS meningitis occurs after this period (most commonly in the first 3 months of life) as an isolated illness characterized by absence of antecedent obstetric or perinatal complications and the presence of more specific signs of meningitis (eg, fever, lethargy, seizures).

Ventriculitis frequently accompanies neonatal bacterial meningitis, particularly when caused by gram-negative enteric bacilli. Organisms that cause meningitis together with severe vasculitis, particularly C. diversus and Cronobacter sakazakii (formerly Enterobacter sakazakii), are likely to cause cysts and abscesses. Pseudomonas aeruginosa, E. coli K1, and Serratia species also may cause brain abscesses. An early clinical sign of brain abscess is increased intracranial pressure (ICP), commonly manifested by vomiting, a bulging fontanelle, and sometimes enlarging head size. Deterioration in an otherwise stable neonate with meningitis suggests progressive increased ICP caused by abscess or hydrocephalus, or rupture of an abscess into the ventricular system.

Pearls & Pitfalls

  • Classic signs of meningitis are uncommon in neonates; a bulging or full fontanelle occurs in only about 25% of neonates and nuchal rigidity occurs in only 15% of neonates.

Diagnosis of Neonatal Bacterial Meningitis

  • Cerebrospinal fluid (CSF) cell counts, glucose and protein levels, Gram stain, and culture

  • Polymerase chain reaction (PCR) testing

  • Sometimes ultrasonography or CT or MRI of the brain

Definitive diagnosis of neonatal bacterial meningitis is made by CSF examination via lumbar puncture (LP), which should be done in any neonate suspected of having sepsis or meningitis. However, LP can be difficult to do in a neonate, and there is some risk of hypoxia. Poor clinical condition (eg, respiratory distress, shock, thrombocytopenia) makes LP risky. If LP is delayed, the neonate should be treated as though meningitis is present. Even when the clinical condition improves, the presence of inflammatory cells and abnormal glucose and protein levels in CSF days after illness onset can still suggest the diagnosis. A needle with a trocar should be used for LP to avoid introducing epithelial rests and subsequent development of epitheliomas.

The CSF, even if bloody or acellular, should be cultured. About 15 to 35% of neonates with negative blood cultures have positive CSF cultures depending on the population studied. If CSF cultures are negative, multiplex PCR panels to test CSF for multiple common pathogens can be done if bacterial meningitis is suspected (eg, if culture may have been affected by prior antibiotic use). LP should be repeated at 24 to 48 hours if clinical response is questionable and at 72 hours when gram-negative organisms are involved (to ensure sterilization).

Repeating the CSF analysis helps guide duration of therapy and predict prognosis. Some experts believe that a repeat LP at 24 to 48 hours in neonates with GBS meningitis has prognostic value. LP should not be repeated at the end of therapy if the neonate is doing well.

Normal CSF values are controversial and in part age-related. In general, both term and preterm infants without meningitis have 20 white blood cells/mcL (one fifth of which may be polymorphonuclear leukocytes) in their CSF. CSF protein levels in the absence of meningitis are more variable; term infants have levels of < 100 mg/dL (1 g/L), whereas preterm infants have levels up to 150 mg/dL (1.5 g/L). CSF glucose levels in the absence of meningitis are > 75% of the serum value measured at the same time. These levels may be as low as 20 to 30 mg/dL (1.1 to 1.7 mmol/L). Bacterial meningitis has been identified by culture in neonates with normal CSF indices, showing that normal CSF values do not exclude a diagnosis of meningitis.

Ventriculitis is suspected in a neonate not responding appropriately to antimicrobial therapy. The diagnosis is made when a ventricular puncture yields a white blood cell count greater than that from the LP, by a positive Gram stain or culture of ventricular fluid, or by increased ventricular pressure. When ventriculitis or brain abscess is suspected, ultrasonography or MRI or CT with contrast may aid diagnosis; dilated ventricles also confirm ventriculitis.

Prognosis for Neonatal Bacterial Meningitis

Without treatment, the mortality rate for neonatal bacterial meningitis approaches 100%. With treatment, prognosis is determined by birth weight, organism, and clinical severity. Mortality rate for treated neonatal bacterial meningitis is 5 to 20%. For organisms that cause vasculitis or brain abscess (necrotizing meningitis), the mortality rate may approach 75%. Neurologic sequelae (eg, hydrocephalus Hydrocephalus Hydrocephalus is accumulation of excessive amounts of CSF, causing cerebral ventricular enlargement and/or increased intracranial pressure. Manifestations can include enlarged head, bulging... read more Hydrocephalus , hearing loss Hearing Impairment in Children Common causes of hearing loss are genetic defects in neonates and ear infections and cerumen in children. Many cases are detected by screening, but hearing loss should be suspected if children... read more Hearing Impairment in Children , intellectual disability Intellectual Disability Intellectual disability is characterized by significantly subaverage intellectual functioning (often expressed as an intelligence quotient 70 to 75) combined with limitations of adaptive functioning... read more ) develop in 20 to 50% of infants who survive, with a poorer prognosis when gram-negative enteric bacilli are the cause.

Prognosis also depends partly on the number of organisms present in CSF at diagnosis. The duration of positive CSF cultures correlates directly with the incidence of complications. In general, CSF cultures from neonates with GBS are usually sterilized within the first 24 hours of antimicrobial therapy. Those from gram-negative bacillary meningitis remain positive longer, with a median of 2 days.

GBS meningitis has a mortality rate significantly lower than that of early-onset GBS sepsis.

Treatment of Neonatal Bacterial Meningitis

  • Empiric ampicillin plus gentamicin, cefotaxime, or both, followed by culture-specific drugs

Empiric antibiotic therapy

Initial empiric treatment depends on patient age and is still debated. For neonates, many experts recommend ampicillin plus an aminoglycoside (see table Recommended Dosages of Select Aminoglycosides for Neonates Recommended Dosages of Select Aminoglycosides for Neonates In neonates, the extracellular fluid (ECF) constitutes up to 45% of total body weight, requiring relatively larger doses of certain antibiotics (eg, aminoglycosides) compared with adults. Lower... read more ). A 3rd-generation cephalosporin (eg, cefotaxime) is also added until culture and sensitivity results are available if meningitis due to a gram-negative organism is suspected. However, resistance may develop more rapidly when cefotaxime is used routinely for empiric therapy, and prolonged use of 3rd-generation cephalosporins is a risk factor for invasive candidiasis. Ampicillin is active against organisms such as GBS, enterococci, and Listeria. Gentamicin provides synergy against these organisms and also treats many gram-negative infections. Third-generation cephalosporins provide adequate coverage for most gram-negative pathogens.

Hospitalized neonates who previously received antibiotics (eg, for early-onset sepsis) may have resistant organisms; fungal disease may also be considered in a septic-appearing neonate after prolonged hospitalization. Ill neonates with hospital-acquired infection should initially receive vancomycin (see table Vancomycin Dosage for Neonates Vancomycin Dosage for Neonates In neonates, the extracellular fluid (ECF) constitutes up to 45% of total body weight, requiring relatively larger doses of certain antibiotics (eg, aminoglycosides) compared with adults. Lower... read more ) plus an aminoglycoside with or without a 3rd-generation cephalosporin or a carbapenem with activity against Pseudomonas aeruginosa, such as cefepime or meropenem, depending on the concern for meningitis.

Antibiotics are adjusted when results of CSF culture and sensitivities are known. The results of the Gram stain should not be used to narrow coverage before culture results are available.

Organism-specific antibiotic therapy

The recommended initial treatment for GBS meningitis in neonates < 1 week of age is penicillin G 100,000 units/kg IV every 6 hours or ampicillin 100 mg/kg IV every 8 hours for infants ≤ 7 days or 75 mg/kg every 6 hours for infants > 7 days. Additionally, gentamicin is given for synergy at age-appropriate dosing (see Table: Recommended Dosages of Select Aminoglycosides for Neonates Recommended Dosages of Select Aminoglycosides for Neonates In neonates, the extracellular fluid (ECF) constitutes up to 45% of total body weight, requiring relatively larger doses of certain antibiotics (eg, aminoglycosides) compared with adults. Lower... read more ). If clinical improvement occurs or sterilization of CSF is documented, gentamicin can be stopped.

For enterococci or L. monocytogenes, treatment is generally ampicillin plus gentamicin for the entire course.

In gram-negative bacillary meningitis, treatment is difficult. The traditional regimen of ampicillin plus an aminoglycoside results in a 15 to 20% mortality rate, with a high rate of sequelae in survivors. Instead, a 3rd-generation cephalosporin (eg, cefotaxime) should be used in neonates with proven gram-negative meningitis. If antibiotic resistance is a concern, both an aminoglycoside and a 3rd-generation cephalosporin or extended-spectrum beta-lactam (eg, meropenem) may be used until sensitivities are known.

Parenteral therapy for gram-positive meningitis is given for a minimum of 14 days, and for complicated gram-positive or gram-negative meningitis, a minimum of 21 days. Intraventricular instillation of antibiotics is not recommended.

Adjunctive measures

Because meningitis may be considered part of the continuum of neonatal sepsis, the adjunctive measures used in treating neonatal sepsis Other treatment Neonatal sepsis is invasive infection, usually bacterial, occurring during the neonatal period. Signs are multiple, nonspecific, and include diminished spontaneous activity, less vigorous sucking... read more should also be used to treat neonatal meningitis. Corticosteroids are not used in treatment of neonatal meningitis. Patients should be closely monitored for neurologic complications during early childhood, including for sensorineural hearing loss.

Key Points

  • The most common causes of neonatal bacterial meningitis are group B streptococcus, E. coli, and L. monocytogenes.

  • Manifestations are often nonspecific (eg, temperature instability, respiratory distress, jaundice, apnea).

  • Although central nervous system signs (eg, lethargy, seizures, vomiting, irritability) may be present, classic findings such as a bulging or full fontanelle and nuchal rigidity are not common.

  • Cerebrospinal fluid (CSF) culture is critical because some neonates with meningitis have normal CSF indices (eg, white blood cell count, protein and glucose levels).

  • Begin empiric treatment with ampicillin, gentamicin, and cefotaxime followed by specific drugs based on the results of cultures and susceptibility testing.

  • Corticosteroids are not used in neonatal meningitis.

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