Flashcards in Bacterial CNS Deck (47):
1
4 major causes of bacterial meningitis
Strep pneumo, neisseria meningitidis, H Flu, Listeria monocytogenes
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CSF in bacterial meningitis usually associated with
large numbers of polys
reduced glucose
elevated protein
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Streptococci morphology
Gram positive spherical bacteria that occur in pairs
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strep pneumo
- also known as pneumococcus
- Normal inhabitants of the upper respiratory tract but MOST COMMON cause of bacterial meningitis in US
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Strep pyogenes
Also known as group A strep, also normal inhabitants of URT
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Strep Agalactiae
Group B strep
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Viridans Streptococci
dental pathogen
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Lancefield classification
An antigenic carbohydrate found in cell walls that determines the Lancefield groups
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Capsular polysaccharide is used to classify what?
Antigenic specificity of S. Pneumoniae
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Strep pneumo disease
- pneumonia (lobar type)
- bacteremia (invasion of tissues and multiplication in the blood)
- Otitis media- infectionsof the ear
- Meningitis: systemic infection which crosses the bbb
case fatality rate of 30 %
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Strep pneumo can alter vascular permeability to allow access to blood stream leading to bacteriemia. Can then directly invade endothelial cells. Cross the blood brain barrier by binding to cerebral capillaries, then transmigrate and enter CSF leading to meningitis
ok...KNOW
12
Strep pneumo virulence factors
- Capsule- interferes with phagocytosis by leukocytes. Interferes with binding of complement to cell surface
- Pilli: The initial event in invasive pneococcus disease is the attachment of encapsulated pneumococci to epithelial cells in the URT.
- Cell wall components-
- Choline binding proteins: major pneumococcal adhesin. Intereacts with carbohydrates on the pulmonary epithelial surface. Important in crossing the blood brain barrier during development of meningitis
- Hemolysins: cause lysis of host cells and activate complement
- Hydrogen peroxide
- Neuraminidase and IgA proteas: Importan tin invasion and destruction of secreted IgA at the mucosal surface.
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Two vaccines for strep pneumo
1) Pneumovax: MULTIVALENT, NON-CONJUGATED, 23 capsule types, for older patients and high risk groups like: HIV, cardiopulmonary, transplant patients, splenic disorders.
Lasts 5-7 years
not effective in infants and young
Protects against invasive pneumococcal disease
2) Prevnar: Heptavalent, 13 groups, conjugated
safe but expensive. Good for infants
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Neisseria morphology
gram negative, non-motile that occur in pairs (diplococci)
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Many Neisseria are part of normal flora
- Two pathogenic neisseria:
Neisseria Gonorrhoea- high prevalence, low mortality
Neisseria Meningitidis: cause of meningococcal meningitis and sepsis. Low prevalence but high mortality
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So if someone is talking about meningococcus meningitis they are referring to what bacteria
Neisseria meningitidis
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N. Meningitidis has a prominent antiphagocytic polysaccharide capsule. This differentiates it from N Gonorrhaea
KNOW
18
What Neisseria meningitidis subgroups cause sporadic (small) outbreaks
B,C,Y
N.M is grouped on the basis of their capsular polysaccharide into 12 serogroups. Those associated with disease are
A, B, C, Y W125
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Epidemic neisseria meningitidis?
Serotype A
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Meningitis belt
sub-saharan africa
- epidemics occur every 5-12 years, last for 2-3 dry seasons and die out during intervening rainy season
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Pathogeneisis of fulminant meningitis from neisseria
Begins abruptly with sudden high fever, stiff neck, chills, myalgias, weakness, NAUSEA, VOMITTING, and headache. Aprehension, restlessness, delirium. Widespread petechial and skin lesions appear suddenly.
Pulmonanry insufficiency then develops and patients will die
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Major toxin of N Meningitidis=
lipooligosaccharide- endotoxin (elicit strong immune response)
the antiphagocytic capsule is also important
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Only known reservoir of N meningitidis
human nasopharynx...spread via respiratory droplets. Aspiration of the infective particles
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Meningococci attach to the nonciliated columnar epithelium of the nasopharynx. Attachment is mediated by pili and possibly other outer membrane components. Invasion of the mucosal cells occurs by a mechanism that involves phase variation (turning off capsule genes then turning them back on once they get in the bloodstream.
KNOW
25
DOC for meningococcemia
Penicillin
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Menomune
N menigitidis vaccine against serogroups A, C, Y, W135
- Unconjugated so there is no memory cmponent
- given to high risk and military
- controls epidemics
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Menactra
Vaccine for serogroups A, C, Y, W135
licensed for use in 11-55 yo
Conjugate so there is memory
Given to all children 11-12 yo
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Neither vaccine covers what serogroup?
B
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High frequency genetic variation of N meningitidis?
Phase variation: changes in expression of a gene leading to on-off control. Remember slip/strand misparing. Many systems employ phase variation
Antigenic Variation: Changes in genes leading to expression of different forms of similar genes. Often involves the pili
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Review phase variation slide 26
ok
31
H influenza
major agent of otitis media, resp disease, and meningitis in YOUNG children
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H influ meningitis cases peak at what age group
6 months of age
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H. Influ isolates classified according to
capsule polysaccharides
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Most important H Influ pathogenic serotype
serotype B
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Chief H flu virulence factor?
capsule
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Chief H flu vaccine
Hib- type B capsular polysaccharide conjugated to a carrier protein. Given to kids between 2 and 15 months
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Look at Listeria
ok
38
Bacterial meningitis causes in birth to 3 mths age group
-Group B
-Gram negative
-Listeria
So Group B strep and listeria can affect the very young
39
3 months to 2 years
strep pneumo
neisseria
H flu
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2 yrs to 18 yrs
Neisseria and Strep pneumo
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Most common cause of bacterial meningitis in an immunocompromised host?
staph
gram negative
pseudomonas
42
Listeria monocytogenes
gram positive rod
- a facultative intracellular parasite
- causes listeriosis, mostly just a flu like condition
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Listeria causes meningitis in who
immune-comprimised adults, pregnant women and infants
Estimated incidence of listeriosis in aids pts is 300 times the incidence in the general population
44
Intrauterine listeria infection often
kills the fetus
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Human reservoir of listeria monocytogenes
intestines
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food borne transmission associated with dairy products, meat, raw veggies
ok
47