You are called to urgently assess a one-month old infant who has been brought into the Emergency Department with a one-day history of fever and irritability progressing to an altered level of consciousness.

She is febrile (38.9ºC), responds only to pain and has a tense anterior fontanelle.

  1. List three diagnoses in addition to CNS infection that need to be considered. (30% marks)
  1. Provide your empiric antimicrobial regimen and discuss your rationale.      (60% marks)

The results of a lumbar puncture are shown below:

Parameter

Patient Value

Adult Normal Range

Glucose

1.4 mmol/L*

2.8 – 4.4

Protein

3.36 g/L*

0.1 – 0.7

Red Cell count

5 cells/high power field

0 – 5

White Cell Count

3220 cells/high power field*

0 – 5

Neutrophils

26%

Lymphocytes

53%

Monocytes

21%

Gram Stain

Occasional Gram-positive bacilli seen

  1. What is the likely cause of this illness? (10% marks)

[Click here to toggle visibility of the answers]

College answer

1)

Post ictal state

Haemorrhage/ oedema secondary to trauma/ non accidental injury

Hydrocephalus

Neoplasm

Spontaneous haemorrhage (e.g. first presentation coagulation disorder)

  1. Need to consider likely organisms causing meningoencephalitis in a neonate, common resistance patterns, penetration of the blood brain barrier.

Likely organisms in this age group: Group B streptococci, Listeria monocytogenes, Varicella zoster virus, Herpes simplex virus, Streptococcus pneumonia, Nesseria meningitides, Haemophilus influenza B (too young to be immunised).

E coli and other gram-negative enteric bacilli less likely at this age than in the first week of life, but not unreasonable to cover.

Regime should include: Acyclovir (HSV, VZV)

A third-generation cephalosporin (cefotaxime, ceftriaxone) to cover gram positives as above and gram-negative cover.

Amoxycillin OR Ben Pen to cover Listeria
Vancomycin to cover resistant Pneumococcus.

  1. Bacterial meningitis, Listeria monocytogenes (require organism for full marks)

Discussion

1) This unconscious febrile neonate with a tense fontanelle: why might they be so, if not infection?

Well: 

  • Vascular causes:
    • SAH or ICH
  • Neoplastic causes
    • Haematological malignancy
  • Drug-induced caused:
    • DRESS syndrome
    • Serotonin syndrome
    • Malignant hyperthermia
  • Idiopathic causes
    • Febrile convulsions (but this does not explain the fontanelle)
    • Hydrocephalus
    • Coalulation disorder and spontaneous ICH
  • Autoimmune causes
    • CNS vasculitis (unlikely in one so young)
  • Traumatic and environmental causes
    • Non-accidental injury (one would certainly need to mention this to score full marks
    • Heat stroke
  • Endocrine and metabolic  causes
    • Metabolic encephalopathy (and the fever is from aspiration)

Empiric antibiotic regimen:

  • Cefotaxime +  ampicillin (Therapeutic Guidelines)
  • Cefotaxime + vancomycin (Sanford guide, paediatric recommendations)
    • The 3rd generation cephalosporins are here for the usual suspects:
      • S. pneumoniae
      • N. meningitidis
      • H. influenzae
    • The one-month-old population is also prone to:
      • S. agalactiae  (group B strep)
      • E.coli
    • The vancomycin in the Sanford recommendations covers the rare (<10%) community-acquired S.pneumoniae with cephalosporin resistance 
    • Sanford people also recommend ampicillin if there is any suspicion of Listeria
    • None of the guidelines recommend antiviral drugs, but they are routinely given anyway

The most likely cause of this illness

  • Connect the dots:
    • Young infant, not exactly immunocompetent
    • Acute onset of illness
    • Low glucose and high protein in the CSF suggests bacterial infection
    • Gram positive bacilli are rare, and include:
      • Bacillus anthracis
      • Corynebacterium diphtheriae
      • Nocardia asteroides
      • Listeria monocytogenes
      • Clostridium sp.
  • The only plausible agent is therefore Listeria.

References

References

NSW Health. Infants and children: acute management of bacterial meningitis: clinical practice guideline. North Sydney: NSW Ministry of Health; 2014.

Tunkel, Allan R., et al. "Practice guidelines for the management of bacterial meningitis." Clinical infectious diseases 39.9 (2004): 1267-1284.