An 82 year old woman presents with fever, seizures and a history of anorexia, diarrhoea and vomiting.
In the above patient, a lumbar puncture is performed following a normal CT scan of head. The immediate results are as follows:
CSF slightly turbid in appearance
300 polymorphs /mm3,
240 monocytes/mm3
Glucose 2.5mmol/L
Protein 0.6 g/l (0.2-0.4 G/L).
a) What is the likely diagnosis?
b) The microbiologist rings to inform you that the gram stain demonstrates numerous small non-branching Gram-positive bacilli. What is the likely diagnosis?
c) What are the appropriate antibiotics for this organism?
d) You discover the patient is allergic to your choice of antibiotic. Suggest an alternative antibiotic.
a) What is the likely diagnosis?
Bacterial Meningitis./ meningoencephalitis.
b) The microbiologist rings to inform you that the gram stain demonstrates numerous small non-branching Gram-positive bacilli. What is the likely diagnosis?
Listeria monocytogenes infection
c) What are the appropriate antibiotics for this organism?
Ampicillin or Penicillin G.
d) You discover the patient is allergic to your choice of antibiotic. Suggest an alternative antibiotic.
IV Bactrim (cotrimoxazole, trimethoprim/sulphamethoxazole)./ Meropenem/ Linezolid-Rifamp combination
The CSF is infected-looking, that is for sure - even though the college does not provide us with an RBC count in the CSF, or with a peripheral BSL. The high protein and the presence of excessive monocytes suggests that meningitis is a likely diagnosis.
Small non-branching Gram-positive bacilli would probably be Listeria monocytogenes, given that meningitis is being discussed. Alternatives include Bacillus anthracis, Corynebacterium diphtheriaeand Nocardia asteroides. However, these bugs are not renowened for their attacks on the cenral nervous system. Clostridium species are even less likely, as they do not thrive in the well-oxygenated environment of the brain.
The most appropriate antibiotics for this woman would be benzylpenicillin. Listeria is very sensitive to this basic antibiotic, and its CNS penetration is enhanced both by the huge doses used in this condition, and by the permeability of the blood-brain barrier in the context of infection. An alternative would be trimethoprim-sulfomethoxazole (Bactrim).
Seeking expert advice, one turns to the Sanford Guide. They recommend ampicillin together with gentamicin for acute Listeria meningitis. In case of allergy, they reach for Bactrim, meropenem or vancomycin.
Tunkel, Allan R., et al. "Practice guidelines for the management of bacterial meningitis." Clinical infectious diseases 39.9 (2004): 1267-1284.