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A 19-year-old woman is admitted with a sudden onset of shivers, severe headache and photophobia. She is tachycardic and has a raised respiratory rate but is normotensive. Her temperature is 39.5 °C.
1. What do you suspect and how would you investigate this?
The history is suggestive of bacterial meningitis. She should have blood cultures taken, throat and peripheral samples sent for NAAT. Her white cell count and C-reactive protein should be measured and she should be assessed for lumbar puncture, which should be performed if there is no evidence of raised intracranial pressure.
2. What would be useful to know from her past medical history?
It would be useful to know about contact with any infectious diseases including childhood viral infections, her immunization history including whether she has had MenC or pneumococcal vaccine as well as MMR, whether she has had any prodrome or if she is from an at-risk group for TB (family exposure, travel exposure).
3. What treatment would you give?
Bacterial meningitis is a medical emergency. Frequently a young, fit adult will appear less ill than they are. Treatment with high-dose ceftriaxone should be instigated before the results of tests are available. This can then be modified in response to laboratory findings. For example if the CSF shows a mildly raised white cell count with predominantly lymphocytes with no organisms seen and a negative culture, it is likely that this is a viral meningitis so antibiotics can be stopped. If on the other hand there is a positive Gram stain or antigen test, antibiotics must be continued and if necessary adjusted to take the culture results into account.
4. What is the most likely cause of bacterial meningitis in this patient?
Until recently the commonest cause of bacterial meningitis was Neisseria meningitidis. Since introduction of the MenC vaccine this has been reduced, so meningitis is now most commonly caused by Streptococcus pneumoniae followed by Neisseria meningitidis type B. A less common cause would be tuberculous meningitis.
5. How would these infections be differentiated clinically?
There is no way to unequivocally differentiate between these infections clinically. If a meningococcal infection is accompanied by bacteraemia, there may be a petechial, non-blanching rash, but meningitis can occur without this. Pneumococcal meningitis is often slower to respond to antibiotics and there are more sequelae, including cranial nerve palsies and hydrocephalus, than with meningococcal meningitis. Worldwide there is an increase in penicillin-resistant pneumococci, so addition of vancomycin therapy may need to be considered. In tuberculous meningitis the onset is likely to be more insidious with a longer prodrome.