Bacterial Meningitis Flashcards
(57 cards)
Is bacterial meningitis a medical emergency?
Yes
Characteristics of bacterial meningitis?
Acute onset and high mortality rate
Signs/Symptoms of bacterial meningitis?
HA, fever, vomiting, photophobia, stiff neck, irritability, varying degree of neurological dysfunction
Identification of bacterial agents?
Spinal tap –> CSF
- Gram stain
- Rapid antigen detection
- PCR testing for specific species in CSF
- Culture of CSF and blood
Characteristics of CSF of bacterial meningitis?
Large number of PMNs (chemotactic response) Reduced glucose (host stress response) elevated protein (BBB breakdown)
What bacterial cause of acute meningitis are typical in children from birth to 3 months?
Grp B Strep
Gram (-) entero
Listeria monocytogenes
What bacterial cause of acute meningitis are typical in children from 3 months to 2 years?
Strep pneumo
Neisseira meningitis
Haemophilus influenzae
What bacterial cause of acute meningitis are typical in children from 2 years to 18 years?
Neisseira meningitis
Strep pneumo
What bacterial cause of acute meningitis are typical in immunocompromised patients?
Neisseira meningitis
Gram (-) entero
Pseudomonas aeruginosa
Characteristics of streptococci?
Gram (+) spherical bacteria that occur in pairs or long chains
What is the most common cause of bacterial meningitis in the US?
Strep pneumo
How are Lancefield classifications determined?
By an anytigenic carbohydrate substance found in cell walls that determines the Lancefield groups A-H & K-U
Which Lancefield groups cause disease in humans?
A,B,C,F, and G
Of what is the amino sugar for grp A?
Grp A - rhamnose-N-acetylglucosamide
Of what is the amino sugar for grp B?
rhamnose-glucosamine
Of what is the amino sugar for grp C?
rhamnose-N-acetylgalactosamine
Of what is the amino sugar for grp D?
glycerol teichoic acid
Of what is the amino sugar for grp F?
glucopyranosyl-N-acetylgalactosamine
What antigenic specificity is used to type. S. pneumo?
Capsular polysaccharides
Colonization of S. pneumo?
- Adhere tightly to the nasopharyngeal epithelium by multiple mechanisms
- May be progression into the lungs or middle ear
- Inflammation in the middle ear is caused by pneumococcal cell wall components resulting in cytotoxicity on ciliated cells of the cochlea
- Upon reaching the lower respiratory tract by aerosol, can progress to the alveolus and associate with specific alveolar cells which produce a choline-containing surfactant
Invasion of S. pneumo?
- Can alter vascular permeability to allow access to the blood stream, leading to lung infections and bacteremia.
- Can directly invade endothelial cells where the bacteria are transported across the cell and bacteria are expelled into the blood stream
- Bacteria can cross the BBB by binding to cerebral capillaries, transmigrate and enter the cerebrospinal fluid leading to meningitis
What are the virulence factors of S. pneumo?
Capsule Pili Cell Wall Components Choline Binding protein Hemolysins:Pneumolysin Hydrogen peroxide Neuroaminidase and IgA protease
How does the virulence factor - capsule work for S. pneumo?
Interferes with phagocytosis by leukocytes.
Resistance to phagocytosis is brought about by interference with binding of complement C3b to the cell surface
How does the virulence factor - pili work for S. pneumo?
Enhances bacterial ability to adhere and invade cells
