Question 26

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.

List three diagnoses in addition to CNS infection that need to be considered. (30% marks)

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

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

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College answer

Post ictal state

Haemorrhage/ oedema secondary to trauma/ non accidental injury

Hydrocephalus

Neoplasm

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

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.

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

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.

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