Diagnostic Considerations

Diagnoses to consider aside from meningitis include the following:

Noninfectious meningitis, including medication-induced meningeal inflammation
Meningeal carcinomatosis
Central nervous system (CNS) vasculitis
Stroke
Encephalitis
All causes of altered mental status and coma
Leptospirosis
Subdural empyema
Parameningeal foci of infection
Seizures
Migraine
Infective endocarditis

Differential Diagnoses

Brain Abscess
Brain Neoplasms
Delirium Tremens (DTs)
Emergent Management of Subarachnoid Hemorrhage
Encephalitis
Febrile Seizures
Herpes Simplex Encephalitis
Herpes Simplex Virus (HSV) in Emergency Medicine
Pediatrics, Meningitis and Encephalitis

Workup

Differential Diagnoses

Brain Abscess
Brain Neoplasms
Delirium Tremens (DTs)
Emergent Management of Subarachnoid Hemorrhage
Encephalitis
Febrile Seizures
Herpes Simplex Encephalitis
Herpes Simplex Virus (HSV) in Emergency Medicine
Pediatrics, Meningitis and Encephalitis

Workup

Cantu RM, M Das J. Viral Meningitis. StatPearls. 2022 Jan. [QxMD MEDLINE Link]. [Full Text].
Runde TJ, Anjum F, Hafner JW. Bacterial Meningitis. StatPearls. 2022 Jan. [QxMD MEDLINE Link]. [Full Text].
National Center for Immunization and Respiratory Diseases. Epidemiology of Meningitis Caused by Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenza. Meningitis Lab Manual. Atlanta, GA: Centers for Disease Control and Prevention; [Full Text].
Brouwer MC, Tunkel AR, van de Beek D. Epidemiology, diagnosis, and antimicrobial treatment of acute bacterial meningitis. Clin Microbiol Rev. 2010 Jul. 23 (3):467-92. [QxMD MEDLINE Link].
Thigpen MC, Whitney CG, Messonnier NE, Zell ER, Lynfield R, Hadler JL, et al. Bacterial meningitis in the United States, 1998-2007. N Engl J Med. 2011 May 26. 364(21):2016-25. [QxMD MEDLINE Link].
Oligbu G, Collins S, Djennad A, et al. Effect of Pneumococcal Conjugate Vaccines on Pneumococcal Meningitis, England and Wales, July 1, 2000-June 30, 2016. Emerg Infect Dis. 2019. 25(9):1708-1718.
Khetsuriani N, Quiroz ES, Holman RC, Anderson LJ. Viral meningitis-associated hospitalizations in the United States, 1988-1999. Neuroepidemiology. 2003 Nov-Dec. 22 (6):345-52. [QxMD MEDLINE Link].
Castelblanco RL, Lee M, Hasbun R. Epidemiology of bacterial meningitis in the USA from 1997 to 2010: a population-based observational study. Lancet Infect Dis. 2014 Sep. 14 (9):813-9. [QxMD MEDLINE Link].
Jaijakul S, Arias CA, Hossain M, Arduino RC, Wootton SH, Hasbun R. Toscana meningoencephalitis: a comparison to other viral central nervous system infections. J Clin Virol. 2012 Nov. 55(3):204-8. [QxMD MEDLINE Link]. [Full Text].
Cordey S, Vu DL, Schibler M, L'Huillier AG, Brito F, Docquier M, et al. Astrovirus MLB2, a New Gastroenteric Virus Associated with Meningitis and Disseminated Infection. Emerg Infect Dis. 2016 May. 22 (5):846-53. [QxMD MEDLINE Link].
Wilson MR, Suan D, Duggins A, Schubert RD, Khan LM, Sample HA, et al. A novel cause of chronic viral meningoencephalitis: Cache Valley virus. Ann Neurol. 2017 Jul. 82 (1):105-114. [QxMD MEDLINE Link].
van de Beek D, de Gans J, Spanjaard L, Weisfelt M, Reitsma JB, Vermeulen M. Clinical features and prognostic factors in adults with bacterial meningitis. N Engl J Med. 2004 Oct 28. 351(18):1849-59. [QxMD MEDLINE Link].
Wright WF, Pinto CN, Palisoc K, Baghli S. Viral (aseptic) meningitis: A review. J Neurol Sci. 2019 Mar 15. 398:176-183. [QxMD MEDLINE Link].
Holmquist L, Russo CA, Elixhauser A. Meningitis-Related Hospitalizations in the United States, 2006: Statistical Brief #57. Healthcare Cost and Utilization Project (HCUP) Statistical Briefs [Internet]. Available at https://www.ncbi.nlm.nih.gov/books/NBK56046/. 2008 Jul;
McGill F, Griffiths MJ, Bonnett LJ, Geretti AM, Michael BD, Beeching NJ, et al. Incidence, aetiology, and sequelae of viral meningitis in UK adults: a multicentre prospective observational cohort study. Lancet Infect Dis. 2018 Sep. 18 (9):992-1003. [QxMD MEDLINE Link].
Hviid A, Melbye M. The epidemiology of viral meningitis hospitalization in childhood. Epidemiology. 2007 Nov. 18 (6):695-701. [QxMD MEDLINE Link].
Cantu RM, M Das J. Viral Meningitis. 2021 Jan. [QxMD MEDLINE Link]. [Full Text].
Kohil A, Jemmieh S, Smatti MK, Yassine HM. Viral meningitis: an overview. Arch Virol. 2021 Feb. 166 (2):335-345. [QxMD MEDLINE Link].
Rotbart HA. Enteroviral Infections of the Central Nervous System. Clin Inf Dis. 1995. 20, no 4:971-81.
Davis LE, DeBiasi R, Goade DE, Haaland KY, Harrington JA, Harnar JB, et al. West Nile virus neuroinvasive disease. Ann Neurol. 2006 Sep. 60 (3):286-300. [QxMD MEDLINE Link].
van Samkar A, Brouwer MC, van der Ende A, van de Beek D. Zoonotic bacterial meningitis in human adults. Neurology. 2016 Sep 13. 87 (11):1171-9. [QxMD MEDLINE Link].
Engelborghs S, Niemantsverdriet E, Struyfs H, Blennow K, et al. Consensus guidelines for lumbar puncture in patients with neurological diseases. Alzheimers Dement (Amst). 2017. 8:111-126. [QxMD MEDLINE Link].
Roos KL. Acute Bacterial Meningitis. Seminal Neurol. 2000. 20(3):293-306.
Durack DT, Spanos A. End-of-treatment spinal tap in bacterial meningitis. Is it worthwhile?. JAMA. 1982 Jul 2. 248 (1):75-8. [QxMD MEDLINE Link].
Huy NT, Thao NT, Diep DT, Kikuchi M, Zamora J, Hirayama K. Cerebrospinal fluid lactate concentration to distinguish bacterial from aseptic meningitis: a systemic review and meta-analysis. Crit Care. 2010. 14 (6):R240. [QxMD MEDLINE Link].
Buch K, Bodilsen J, Knudsen A, Larsen L, Helweg-Larsen J, Storgaard M, et al. Cerebrospinal fluid lactate as a marker to differentiate between community-acquired acute bacterial meningitis and aseptic meningitis/encephalitis in adults: a Danish prospective observational cohort study. Infect Dis (Lond). 2018 Jul. 50 (7):514-521. [QxMD MEDLINE Link].
Park IU, Tran A, Pereira L, Fakile Y. Sensitivity and Specificity of Treponemal-specific Tests for the Diagnosis of Syphilis. Clin Infect Dis. 2020 Jun 24. 71 (Suppl 1):S13-S20. [QxMD MEDLINE Link].
Tyler KL, Pape J, Goody RJ, Corkill M, Kleinschmidt-DeMasters BK. CSF findings in 250 patients with serologically confirmed West Nile virus meningitis and encephalitis. Neurology. 2006 Feb 14. 66 (3):361-5. [QxMD MEDLINE Link].
Remy MM, Schöbi N, Kottanattu L, Pfister S, Duppenthaler A, Suter-Riniker F. Cerebrospinal fluid CXCL13 as a diagnostic marker of neuroborreliosis in children: a retrospective case-control study. J Neuroinflammation. 2017 Aug 31. 14 (1):173. [QxMD MEDLINE Link].
Dubos F, Korczowski B, Aygun DA, Martinot A, Prat C, Galetto-Lacour A, et al. Serum procalcitonin level and other biological markers to distinguish between bacterial and aseptic meningitis in children: a European multicenter case cohort study. Arch Pediatr Adolesc Med. 2008 Dec. 162(12):1157-63. [QxMD MEDLINE Link].
Beattie GC, Glaser CA, Sheriff H, Messenger S, Preas CP, Shahkarami M, et al. Encephalitis with thalamic and basal ganglia abnormalities: etiologies, neuroimaging, and potential role of respiratory viruses. Clin Infect Dis. 2013 Mar. 56 (6):825-32. [QxMD MEDLINE Link].
Berwal A, Chawla K, Vishwanath S, Shenoy VP. Role of multiplex polymerase chain reaction in diagnosing tubercular meningitis. J Lab Physicians. 2017 Apr-Jun. 9 (2):145-147. [QxMD MEDLINE Link].
Bahr NC, Nuwagira E, Evans EE, Cresswell FV, Bystrom PV, Byamukama A, et al. Diagnostic accuracy of Xpert MTB/RIF Ultra for tuberculous meningitis in HIV-infected adults: a prospective cohort study. Lancet Infect Dis. 2018 Jan. 18 (1):68-75. [QxMD MEDLINE Link].
Schmidt C, Plate A, Angele B, Pfister HW, Wick M, Koedel U, et al. A prospective study on the role of CXCL13 in Lyme neuroborreliosis. Neurology. 2011 Mar 22. 76 (12):1051-8. [QxMD MEDLINE Link].
Eckman EA, Clausen DM, Herdt AR, Pacheco-Quinto J, Halperin JJ. Specificity and Diagnostic Utility of Cerebrospinal Fluid CXCL13 in Lyme Neuroborreliosis. Clin Infect Dis. 2021 May 18. 72 (10):1719-1726. [QxMD MEDLINE Link].
Gilbert DN, Moellering RC Jr, Sande MA. Antimicrobial Therapy. In: Sanford Guide to Antimicrobial Therapy. 33rd ed. March 15, 2003.
Kastrup O, Wanke I, Maschke M. Neuroimaging of infections. NeuroRx. 2005 Apr. 2 (2):324-32. [QxMD MEDLINE Link].
Baheerathan A, Pitceathly RD, Curtis C, Davies NW. CSF lactate. Pract Neurol. 2020 Aug. 20 (4):320-323. [QxMD MEDLINE Link].
Sulaiman T, Salazar L, Hasbun R. Acute versus subacute community-acquired meningitis: Analysis of 611 patients. Medicine (Baltimore). 2017 Sep. 96 (36):e7984. [QxMD MEDLINE Link].
van de Beek D, Brouwer MC, Thwaites GE, Tunkel AR. Advances in treatment of bacterial meningitis. Lancet. 2012 Nov 10. 380(9854):1693-702. [QxMD MEDLINE Link].
Mera RM, Miller LA, Amrine-Madsen H, Sahm DF. Impact of new Clinical Laboratory Standards Institute Streptococcus pneumoniae penicillin susceptibility testing breakpoints on reported resistance changes over time. Microb Drug Resist. 2011 Mar. 17(1):47-52. [QxMD MEDLINE Link].
Gouveia EL, Reis JN, Flannery B, Cordeiro SM, Lima JB, Pinheiro RM, et al. Clinical outcome of pneumococcal meningitis during the emergence of pencillin-resistant Streptococcus pneumoniae: an observational study. BMC Infect Dis. 2011 Nov 21. 11:323. [QxMD MEDLINE Link]. [Full Text].
Brouwer MC, Heckenberg SG, de Gans J, Spanjaard L, Reitsma JB, van de Beek D. Nationwide implementation of adjunctive dexamethasone therapy for pneumococcal meningitis. Neurology. 2010 Oct 26. 75(17):1533-9. [QxMD MEDLINE Link].
[Guideline] Tunkel AR, Hartman BJ, Kaplan SL, Kaufman BA, Roos KL, Scheld WM, et al. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis. 2004 Nov 1. 39(9):1267-84. [QxMD MEDLINE Link].
van de Beek D, de Gans J, McIntyre P, Prasad K. Steroids in adults with acute bacterial meningitis: a systematic review. Lancet Infect Dis. 2004 Mar. 4(3):139-43. [QxMD MEDLINE Link].
Brouwer MC, McIntyre P, de Gans J, Prasad K, van de Beek D. Corticosteroids for acute bacterial meningitis. Cochrane Database Syst Rev. 2010 Sep 8. CD004405. [QxMD MEDLINE Link].
van de Beek D, Farrar JJ, de Gans J, Mai NT, Molyneux EM, Peltola H, et al. Adjunctive dexamethasone in bacterial meningitis: a meta-analysis of individual patient data. Lancet Neurol. 2010 Mar. 9(3):254-63. [QxMD MEDLINE Link]. [Full Text].
Peltola H, Roine I. Improving the outcomes in children with bacterial meningitis. Curr Opin Infect Dis. 2009 Jun. 22(3):250-5. [QxMD MEDLINE Link].
van de Beek D, Drake JM, Tunkel AR. Nosocomial bacterial meningitis. N Engl J Med. 2010 Jan 14. 362(2):146-54. [QxMD MEDLINE Link].
Sloan D, Dlamini S, Paul N, Dedicoat M. Treatment of acute cryptococcal meningitis in HIV infected adults, with an emphasis on resource-limited settings. Cochrane Database Syst Rev. 2008 Oct 8. CD005647. [QxMD MEDLINE Link].
Kauffman CA, Bustamante B, Chapman SW, Pappas PG. Clinical practice guidelines for the management of sporotrichosis: 2007 update by the Infectious Diseases Society of America. Clin Infect Dis. 2007 Nov 15. 45(10):1255-65. [QxMD MEDLINE Link].
Treatment of tuberculosis. MMWR Recomm Rep. 2003 Jun 20. 52:1-77. [QxMD MEDLINE Link].
El Sahly H, Udayamurthy M, Parkerson G, Hasbun R. Survival of an AIDS patient after infection with Acanthamoeba sp. of the central nervous system. Infection. 2017 Oct. 45 (5):715-718. [QxMD MEDLINE Link].
Report from the Advisory Committee on Immunization Practices (ACIP): decision not to recommend routine vaccination of all children aged 2-10 years with quadrivalent meningococcal conjugate vaccine (MCV4). MMWR Morb Mortal Wkly Rep. 2008 May 2. 57(17):462-5. [QxMD MEDLINE Link].
[Guideline] Updated recommendations for use of meningococcal conjugate vaccines --- Advisory Committee on Immunization Practices (ACIP), 2010. MMWR Morb Mortal Wkly Rep. 2011 Jan 28. 60(3):72-6. [QxMD MEDLINE Link].
FDA News Release: First vaccine approved by FDA to prevent serogroup B Meningococcal disease. Available at http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm420998.htm. Accessed: October 29, 2014.
FDA News Release. FDA approves a second vaccine to prevent serogroup B meningococcal disease. Available at http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm431370.htm. Accessed: January 23, 2015.
Nuorti JP, Whitney CG. Prevention of pneumococcal disease among infants and children - use of 13-valent pneumococcal conjugate vaccine and 23-valent pneumococcal polysaccharide vaccine - recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2010 Dec 10. 59:1-18. [QxMD MEDLINE Link].
Tomczyk S, Bennett NM, Stoecker C, Gierke R, Moore MR, Whitney CG, et al. Use of 13-valent pneumococcal conjugate vaccine and 23-valent pneumococcal polysaccharide vaccine among adults aged =65 years: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep. 2014 Sep 19. 63(37):822-5. [QxMD MEDLINE Link]. [Full Text].
[Guideline] Tunkel AR, Hasbun R, Bhimraj A, Byers K, Kaplan SL, Michael Scheld W, et al. 2017 Infectious Diseases Society of America's Clinical Practice Guidelines for Healthcare-Associated Ventriculitis and Meningitis. Clin Infect Dis. 2017 Feb 14. [QxMD MEDLINE Link].

Media Gallery

Pneumococcal meningitis in a patient with alcoholism. Courtesy of the CDC/Dr. Edwin P. Ewing, Jr.
Acute bacterial meningitis. This axial nonenhanced computed tomography scan shows mild ventriculomegaly and sulcal effacement.
Acute bacterial meningitis. This axial T2-weighted magnetic resonance image shows only mild ventriculomegaly.
Acute bacterial meningitis. This contrast-enhanced, axial T1-weighted magnetic resonance image shows leptomeningeal enhancement (arrows).
Chronic mastoiditis and epidural empyema in a patient with bacterial meningitis. This axial computed tomography scan shows sclerosis of the temporal bone (chronic mastoiditis), an adjacent epidural empyema with marked dural enhancement (arrow), and the absence of left mastoid air.
Subdural empyema and arterial infarct in a patient with bacterial meningitis. This contrast-enhanced axial computed tomography scan shows left-sided parenchymal hypoattenuation in the middle cerebral artery territory, with marked herniation and a prominent subdural empyema.

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Table 1. Most Common Bacterial Pathogens on Basis of Age and Predisposing Risks

Risk or Predisposing Factor	Bacterial Pathogen
Age 0-4 weeks	Streptococcus agalactiae (GBS) Escherichia coli K1 Listeria monocytogenes
Age 4-12 weeks	S agalactiae E coli Haemophilus influenzae Streptococcus pneumoniae Neisseria meningitidis
Age 3 months to 18 years	N meningitidis S pneumoniae H influenzae
Age 18-50 years	S pneumoniae N meningitidis H influenzae
Age >50 years	S pneumoniae N meningitidis L monocytogenes Aerobic gram-negative bacilli
Immunocompromised state	S pneumoniae N meningitidis L monocytogenes Aerobic gram-negative bacilli
Intracranial manipulation, including neurosurgery	Staphylococcus aureus Coagulase-negative staphylococci Aerobic gram-negative bacilli, including Pseudomonas aeruginosa
Basilar skull fracture	S pneumoniae H influenzae Group A streptococci
CSF shunts	Coagulase-negative staphylococci S aureus Aerobic gram-negative bacilli Propionibacterium acnes
CSF = cerebrospinal fluid; GBS = group B streptococcus.

Table 2. Infectious Agents Causing Aseptic Meningitis

Category	Agent
Bacteria	Partially treated bacterial meningitis Listeria monocytogenes Brucella spp Rickettsia rickettsii Ehrlichia spp Mycoplasma pneumoniae Borrelia burgdorferi Treponema pallidum Leptospira spp Mycobacterium tuberculosis Nocardia spp
Parasites	Naegleria fowleri Acanthamoeba spp Balamuthia spp Angiostrongylus cantonensis Gnathostoma spinigerum Baylisascaris procyonis Strongyloides stercoralis Taenia solium (cysticercosis) Toxocara spp
Fungi	Cryptococcus neoformans Coccidioides immitis Blastomyces dermatitidis Histoplasma capsulatum Candida spp Aspergillus spp
Viruses	Enterovirus	Poliovirus Echovirus Coxsackievirus A Coxsackievirus B Enterovirus 68-71
	Herpesvirus (HSV)	HSV-1 and HSV-2 Varicella-zoster virus Epstein-Barr virus Cytomegalovirus HHV-6 and HHV-7
	Paramyxovirus	Mumps virus Measles virus
	Togavirus	Rubella virus
	Flavivirus	West Nile virus Japanese encephalitis virus St Louis encephalitis virus
	Bunyavirus	California encephalitis virus La Crosse encephalitis virus
	Alphavirus	Eastern equine encephalitis virus Western equine encephalitis virus Venezuelan encephalitis virus
	Reovirus	Colorado tick fever virus
	Arenavirus		LCM virus
	Rhabdovirus		Rabies virus
	Retrovirus		HIV
HHV = human herpesvirus; HSV = herpes simplex virus; LCM = lymphocytic choriomeningitis.

Table 3. Causes of Chronic Meningitis

Category	Agent
Bacteria	Mycobacterium tuberculosis Borrelia burgdorferi Treponema pallidum Brucella spp Francisella tularensis Nocardia spp Actinomyces spp
Fungi	Cryptococcus neoformans Coccidioides immitis Blastomyces dermatitidis Histoplasma capsulatum Candida albicans Aspergillus spp Sporothrix schenckii
Parasites	Acanthamoeba spp Naegleria fowleri Angiostrongylus cantonensis Gnathostoma spinigerum Baylisascarisprocyonis Schistosoma spp Strongyloides stercoralis Echinococcus granulosus

Table 4. Changing Epidemiology of Acute Bacterial Meningitis in United States*

Bacteria	1978-1981	1986	1995	1998-2007
Haemophilus influenzae	48%	45%	7%	6.7%
Listeria monocytogenes	2%	3%	8%	3.4%
Neisseria meningitidis	20%	14%	25%	13.9%
Streptococcus agalactiae (group B streptococcus)	3%	6%	12%	18.1%
Streptococcus pneumoniae	13%	18%	47%	58%
*Nosocomial meningitis is not included; these data include only the 5 major meningeal pathogens.

Other Exposures and Organisms Associated with Meningitis

Animal exposure	Organism associated with meningitis
Dog	Brucella B henselae C canimorus C cynodegmi Leptospira M avium P multocida Rabies
Cat	B henselae C canimorsus C cynodegmi M avium P multocida
Cow	B anthracis Brucella C fetus C burnetii Leptospira M bovis
Sheep	Brucella C fetus C burnetii
Pig	Brucella Leptospira M avium M bovis P multocida S suis
Goat	Brucella C fetus C burnetiid S equi
Horse	Leptospira M avium S equi
Rabbits/squirrel	F tularensis Leptospira M avium Yersinia pestis
Fish	Streptococcus iniae
Rodents (hamster, rats, mice)	Lymphocytic choriomeningitis virus
Mosquito	Yellow fever Plasmodium sp ( Malaria ) Japanese encephalitis West Nile Virus St Louis California encephalitis group of viruses Dengue virus Chikungunya virus Zika virus
Bats	Rabies Australian Bat Lyssavirus Nipah Virus
Ticks	Borrelia burgdorferi (Lyme’s disease) Ehrlichia Rocky Mountain spotted fever Anaplasma Powassan virus Coltivirus (Colarado tick fever)
Sandflies	Toscana virus

Table 6. CSF Findings in Meningitis by Etiologic Agent

Agent	Opening Pressure (mm H₂O)	WBC count (cells/µL)	Glucose (mg/dL)	Protein (mg/dL)	Microbiology
Bacterial meningitis	200-300	100-5000; >80% PMNs	< 40	>100	Specific pathogen demonstrated in 60% of Gram stains and 80% of cultures
Viral meningitis	90-200	10-300; lymphocytes	Normal, reduced in LCM and mumps	Normal but may be slightly elevated	Viral isolation, PCR assays
Tuberculous meningitis	180-300	100-500; lymphocytes	Reduced, < 40	Elevated, >100	Acid-fast bacillus stain, culture, PCR
Cryptococcal meningitis	180-300	10-200; lymphocytes	Reduced	50-200	India ink, cryptococcal antigen, culture
Aseptic meningitis	90-200	10-300; lymphocytes	Normal	Normal but may be slightly elevated	Negative findings on workup
Normal values	80-200	0-5; lymphocytes	50-75	15-40	Negative findings on workup
LCM = lymphocytic choriomeningitis; PCR = polymerase chain reaction; PMN = polymorphonuclear leukocyte; WBC = white blood cell.

Table 7. Comparison of CSF Findings by Type of Organism

Normal Finding	Bacterial Meningitis	Viral Meningitis*	Fungal Meningitis**
Pressure (mm H₂O) 50-150	Increased	Normal or mildly increased	Normal or mildly increased in tuberculous meningitis; may be increased in fungal; AIDS patients with cryptococcal meningitis have increased risk of blindness and death unless kept below 300 mm H₂O
Cell count (mononuclear cells/µL) Preterm: 0-25 Term: 0-22 >6 months: 0-5	No cell count result can exclude bacterial meningitis; PMN count typically in 1000s but may be less dramatic or even normal (classically, in very early meningococcal meningitis and in extremely ill neonates); lymphocytosis with normal CSF chemistries seen in 15-25%, especially when cell counts < 1000 or with partial treatment; ~90% of patients with ventriculoperitoneal shunts who have CSF WBC count >100 are infected; CSF glucose is usually normal, and organisms are less pathogenic; cell count and chemistries normalize slowly (over days) with antibiotics	Cell count usually < 500, nearly 100% mononuclear; up to 48 hours, significant PMN pleocytosis may be indistinguishable from early bacterial meningitis; this is particularly true with eastern equine encephalitis; presence of nontraumatic RBCs in 80% of HSV meningoencephalitis, though 10% have normal CSF results	Hundreds of mononuclear cells
Microscopy No organisms	Gram stain 80% sensitive; inadequate decolorization may mistake Haemophilus influenzae for gram-positive cocci; pretreatment with antibiotics may affect stain uptake, causing gram-positive organisms to appear gram-negative and decrease culture yield by average of 20%	No organism	India ink is 50% sensitive for fungi; cryptococcal antigen is 95% sensitive; AFB stain is 40% sensitive for tuberculosis (increase yield by staining supernatant from at least 5 mL CSF)
Glucose Euglycemia: >50% serum Hyperglycemia: >30% serum Wait 4 hr after glucose load	Decreased	Normal	Sometimes decreased; aside from fulminant bacterial meningitis, lowest levels of CSF glucose are seen in tuberculous meningitis, primary amebic meningoencephalitis, and neurocysticercosis
Protein (mg/dL) Preterm: 65-150 Term: 20-170 >6 months: 15-45	Usually >150, may be >1000	Mildly increased	Increased; >1000 with relatively benign clinical presentation suggestive of fungal disease
AFB = acid-fast bacillus; CSF = cerebrospinal fluid; HSV = herpes simplex virus; RBC = red blood cell; PMN = polymorphonuclear leukocyte. Some bacteria (eg, Mycoplasma, Listeria, Leptospira spp, Borrelia burgdorferi [Lyme], and spirochetes) produce spinal fluid alterations that resemble the viral profile. An aseptic profile also is typical of partially treated bacterial infections (>33% of patients have received antimicrobial treatment, especially children) and the 2 most common causes of encephalitis—the potentially curable HSV and arboviruses. *In contrast, tuberculous meningitis and parasites resemble the fungal profile more closely.

Table 7. Recommended Empiric Antibiotics for Suspected Bacterial Meningitis, According to Age or Predisposing Factors ^[40]

Age or Predisposing Feature	Antibiotics
Age 0-4 wk	Ampicillin plus either cefotaxime or an aminoglycoside
Age 1 mo-50 y	Vancomycin plus cefotaxime or ceftriaxone*
Age >50 y	Vancomycin plus ampicillin plus ceftriaxone or cefotaxime plus vancomycin*
Impaired cellular immunity	Vancomycin plus ampicillin plus either cefepime or meropenem
Recurrent meningitis	Vancomycin plus cefotaxime or ceftriaxone
Basilar skull fracture	Vancomycin plus cefotaxime or ceftriaxone
Head trauma, neurosurgery, or CSF shunt	Vancomycin plus ceftazidime, cefepime, or meropenem
CSF = cerebrospinal fluid. Add ampicillin if Listeria monocytogenes* is a suspected pathogen.

Table 8. Specific Antibiotics and Duration of Therapy for Acute Bacterial Meningitis

Bacteria	Susceptibility	Antibiotic(s)	Duration (days)
Streptococcus pneumoniae	Penicillin MIC ≤0.06 μg/mL	Recommended: Penicillin G or ampicillin Alternatives: Cefotaxime, ceftriaxone, chloramphenicol	10-14
	Penicillin MIC ≥0.12 μg/mL Cefotaxime or ceftriaxone MIC ≥0.12 μg/mL	Recommended: Cefotaxime or ceftriaxone Alternatives: Cefepime, meropenem
	Cefotaxime or ceftriaxone MIC ≥1.0 μg/mL	Recommended: Vancomycin plus cefotaxime or ceftriaxone Alternatives: Vancomycin plus moxifloxacin
Haemophilus influenzae	Beta-lactamase−negative	Recommended: Ampicillin Alternatives: Cefotaxime, ceftriaxone, cefepime, chloramphenicol, aztreonam, a fluoroquinolone	7
	Beta-lactamase−positive	Recommended: Cefotaxime or ceftriaxone Alternatives: Cefepime, chloramphenicol, aztreonam, a fluoroquinolone
	Beta-lactamase−negative, ampicillin-resistant	Recommended: Meropenem Alternatives: Cefepime, chloramphenicol, aztreonam, a fluoroquinolone
Neisseria meningitidis	Penicillin MIC < 0.1 μg/mL	Recommended: Penicillin G or ampicillin Alternatives: Cefotaxime, ceftriaxone, chloramphenicol	7
Neisseria meningitidis	Penicillin MIC ≥0.1 μg/mL	Recommended: Cefotaxime or ceftriaxone Alternatives: Cefepime, chloramphenicol, a fluoroquinolone, meropenem	7
Listeria monocytogenes	...	Recommended: Ampicillin or penicillin G Alternative: TMP-SMX	14-21
Streptococcus agalactiae	...	Recommended: Ampicillin or penicillin G Alternatives: Cefotaxime, ceftriaxone, vancomycin	14-21
Enterobacteriaceae	...	Recommended: Cefotaxime or ceftriaxone Alternatives: Aztreonam, a fluoroquinolone, TMP-SMX, meropenem, ampicillin	21
Pseudomonas aeruginosa	...	Recommended: Ceftazidime or cefepime Alternatives: Aztreonam, meropenem, ciprofloxacin	21
Staphylococcus epidermidis		Recommended: Vancomycin Alternative: Linezolid Consider addition of rifampin
MIC= minimal inhibitory concentration; TMP-SMX = trimethoprim-sulfamethoxazole.

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Author

Shikha S Vasudeva, MBBS Assistant Professor of Internal Medicine, Virginia Tech Carilion School of Medicine; Assistant Professor of Internal Medicine, Edward Via Virginia College of Osteopathic Medicine; Infectious Disease Consultant, Department of Medicine, Veterans Affair Medical Center

Shikha S Vasudeva, MBBS is a member of the following medical societies: Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Chief Editor

Michael Stuart Bronze, MD David Ross Boyd Professor and Chairman, Department of Medicine, Stewart G Wolf Endowed Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center; Master of the American College of Physicians; Fellow, Infectious Diseases Society of America; Fellow of the Royal College of Physicians, London

Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Medical Association, Association of Professors of Medicine, Infectious Diseases Society of America, Oklahoma State Medical Association, Southern Society for Clinical Investigation

Disclosure: Nothing to disclose.

Additional Contributors

Rodrigo Hasbun, MD, MPH Associate Professor of Medicine, Section of Infectious Diseases, University of Texas Medical School at Houston

Disclosure: Received research grant from: Biofire<br/> Speaker for Biofire.

Acknowledgements

Suur Biliciler, MD Neuromuscular Fellow, Department of Neurology, Baylor College of Medicine