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Bacterial Meningitis


 

Perhaps no admission causes so much consternation and dread amongst caregivers and families as a case of suspected bacterial meningitis. Will the patient live? What infection control precautions are necessary? And, perhaps most urgently, do I need antibiotic prophylaxis? In this article I answer the questions hospitalists most often need to address in such circumstances.

1. Who should have a head CT prior to lumbar puncture (LP) for suspected meningitis? Patients with immunocompromise, papilledema, preexisting CNS disease, new onset seizures, altered level of consciousness, and focal neurological findings should have a head CT prior to LP.1 While herniation is rare after LP for purulent meningitis, patients with increased intracranial pressure at risk for herniation often have normal head CT scans. Therefore, herniation may be an uncommon but unpredictable complication of LP in this setting. The cause-and-effect relationship of herniation and LP has also been questioned.

2. Are there any cerebrospinal fluid (CSF) findings that exclude bacterial meningitis? A number of CSF findings make bacterial meningitis quite likely, including total leukocyte counts of more than 2,000/mm3, a positive gram stain, or very low CSF glucose. It is difficult, if not impossible, however, to exclude bacterial meningitis in patients with any degree of CSF pleocytosis. For example, 10% of patients with bacterial meningitis have less than 100 WBCs/mm3 in CSF, and 10% have lymphocyte predominance at presentation. Therefore, the safest course of action when bacterial meningitis is suspected on clinical grounds and CSF pleocytosis is present is to continue antibiotics until results of CSF cultures are available.

3. Which patients with suspected or proven meningitis should receive steroids? Steroids reduce neurologic damage from the inflammatory surge provoked by antibiotic-induced pneumococcal lysis. In a large European trial, dexamethasone given in 10-mg doses every six hours for four days (before or with the first dose of antibiotics) reduced mortality in pneumococcal meningitis.2 Benefits were not seen in patients with bacterial meningitis from other pathogens. Dexamethasone can be safely stopped as soon as pneumococcal meningitis is excluded.

4. How soon should patients receive antibiotics? When bacterial meningitis is likely, antibiotics should be given immediately, prior to imaging studies and lumbar puncture. In patients with a lower clinical likelihood of bacterial meningitis, antibiotics can be deferred, awaiting the results of diagnostic studies.

5. What empiric antibiotic therapy is appropriate? Adults 18-50 with suspected bacterial meningitis should receive therapy directed against Streptococcus pneumoniae and Neisseria meningitidis. Vancomycin should be dosed to achieve a relatively high trough level of 15-20 mcg/mL. For a 70-kg adult male with normal renal function, doses of vancomycin given at the rate of 1.5 gm IV every 12 hours and ceftriaxone at 2 gm IV every 12 hours are appropriate. Adults over 50, alcoholics, and immunocompromised adults of any age should also receive ampicillin doses of 2 gm IV every four hours to cover Listeria, in addition to vancomycin and ceftriaxone.3,4

6. What infection control precautions are required? Meningococcal meningitis patients should be placed on droplet precautions (private room, mask for all entering the room) until they have completed 24 hours of appropriate antibiotic therapy. Negative pressure ventilation is not required. Patients with pneumococcal or viral meningitis do not require isolation.

7. Who needs antibiotic prophylaxis after patient exposure? Chemoprophylaxis is overprescribed after exposures to patients with meningococcal meningitis. The only social contacts who should receive prophylaxis are household contacts, childcare contacts, and people who have had direct exposure to the patient’s oral secretions through actions such as kissing or sharing utensils or toothbrushes. The only healthcare workers requiring chemoprophylaxis are those who performed mouth-to-mouth resuscitation or any staff who were unmasked during intubation or suctioning of a patient. Regimens for chemoprophylaxis in adults include ciprofloxacin, 500 mg taken orally as a single dose, rifampin taken in doses of 600 mg twice daily for two days, or 250 mg of ceftriaxone, given intramuscularly. Ceftriaxone is preferred for pregnant women. Chemoprophylaxis is unnecessary after exposure to patients with pneumococcal or viral meningitis.

8. What is the significance of arthritis after meningococcal meningitis? A significant number of patients with meningococcal disease develop inflammatory polyarthritis about a week after the onset of infection. In most cases, this is a sterile, immune complex phenomenon that responds to anti-inflammatory therapy. If joint effusions are present, they should be aspirated to exclude septic arthritis and crystalline arthritis. TH

Dr. Ross is a hospitalist at Brigham and Women’s Hospital (Boston) and a fellow of the Infectious Diseases Society of America.

References

  1. Hasbun R, Abrahams J, Jekel J, et al. Computed tomography of the head before lumbar puncture in adults with suspected meningitis. N Engl J Med. 2001 Dec 13;345(24):1727-1733.
  2. de Gans J, van de Beek D. Dexamethasone in adults with bacterial meningitis. European dexamethasone in adulthood bacterial meningitis. N Engl J Med. 2002;347(20):1549-156.
  3. Tunkel AR, Hartman BJ, Kaplan SL, et al. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis. 2004 Nov 1;39(9):1267-1284.
  4. van de Beek D, de Gans J, Tunkel AR, et al. Community-acquired bacterial meningitis in adults. N Engl J Med. 2006 Jan 5;354(1):44-53.

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