I. Bacterial Meningitis Board ReviewBacterial Epidemiology
Neonates Infant (<6 mo) Children 2yr – 19yr 20yr – 60yr >60yr
E. Coli E. Coli Strep Pneum Neisseria Strep Pneum Strep Pneum
Group B
Strep
Group B
Strep
Neisseria Strep Pneum Neisseria Group B
Strep
Listeria Strep Pneum Listeria
* Tables borrowed from Dr. Lesse’s lecture on Bacterial Meningitis
Spinal Fluid Formula Leukocytes Proteins Glucose
Bacterial >100, mainly
neutrophils
100-500 <40
Viral 10-500 Slightly
elevated
Normal
Fungal 50-500 mainly
lymphs
50-150 Low
TB 100-500 mainly
lymphs
100-500,
possibly higher
Low
Neuroscience and BehaviorUSMLE Review
Treatment: Initialtherapy ofteninvolves broadcoverage, such asCeftriaxone. Ifthe patient is veryyoung (<3mo),then useAmpicillin. Canadd vancomycinfor additionalcoverage.
Meningeal Pathogens ReviewKnow how todifferentiatepneumococcusfrom S. viridans;Optochin willinhibit growth ofpneumococcusand NOT viridansAlpha = partialBeta = completeGamma = none
Quick Hit
A. Streptococcus pneumoniae (pneumococcus)
- Gram positive, alpha hemolytic bacteria in pairs
• most common cause of pneumonia in
adults, most common cause of meningitis is
adults >20 yrs old, and most common cause
of otitis media
- major virulence factor is its polysaccharide
capsule, which protects it from phagocytosis
- Pneumococcal vaccine – Pneumovax, contains polysaccharides from the 23 most
prevalent antigens; should be given to elderly, immunocompromised, aplenics, HIV+ pts
*http://www.meddean.luc.edu/lumen/DeptWebs/microbio/med/gram/slides/slide8.htm
Board Favorite -Be able to easilydifferentiatebacterial fromviral meningitis.
Quick Hit
Look for USMLEquestions involvingNeisseria to affectmilitary recruits orcollege students
Quick Hit
B. Neisseria meningitidis (meningococcus)
- Gram negative, bean shaped diplococci; polysaccharide capsule, IgA protease+
- classic growth media: Thayer-Martin VCN media (chocolate agar)
• leading cause of meningitis in young adults, can release an
endotoxin (LPS) which can cause petechiae and damage
adrenal glands
- Meningococcemia – intravascular multiplication of
meningococcus can cause spiking fevers, chills, arthralgias,
muscle pains, and petechial rash
• meningitis begins suddenly, with severe headache, fever,
+kernig’s sign, photophobia, and sometimes petechiae
*http://embryology.med.unsw.edu.au/Defect/images/Neisseria-meningitidis2.jpg
C. Listeria monocytogenes
- Gram positive, non-spore forming, motile rod
***the only gram-positive organism with endotoxin (LPS-Lipid A)
• causes meningitis in immunocompromised, neonates, and elderly
- can grow at extremely low temperatures; associated with milk products
If you see abruptonset hypotensionand tachycardia,along withpetechial lesions,think Waterhouse- Friderichsensyndrome(adrenalhemorrhage)
Quick Hit
Endotoxin isLipid A. It isonly present inGram-negativebacteria, exceptListeria
Quick Hit
*Images taken from Loyola University Microbiology and Immunology, and the University of New South Wales Embryology websites
