Micro: Greenberg 2 Flashcards
What are the common agents of bacterial meningitis in infants, children and adults?
acquired via respiratory droplets
s. pneumoniae, n. meningitidis, H. flu type b
What are the common agents of bacterial meningitis in neonates?
acquired via maternal genital tract
s. agalactiae (group b strep), listeria, e. coli
What is the microbiology of s. pneumoniae?
*gram+ cocci in pairs and short chains, alpha hemolytic
catalase negative, optochin sensitive, sensitive to bile lysis
What are risk factors for s. pneumo?
*cochlear implant or CSF leak
65, asplenic, alcoholic, HIV, diabetes, HIV, defects in humoral immunity, acquisition of new strain
What are some virulence factors of s. pneumo?
pneumolysin
polysaccharide capsule
What is the role of pneumolysin of s. pneumo?
pore-forming cytotoxin, lytic to host cells, impairs respiratory burst, induces inflammatory cytokines
What is the role of the polysaccharide capsule of s. pneumo?
major virulence determinant
anti-phagocytic
negatively charged and inhibits: interxn of Fc stem and receptor, interxn of CR3 and iC3b
How is s. pneumo diagnosed?
culture from CSF or blood
rapid antigen detection test for CAP and meningitis (adults) - test both urine and CSF
What is the treatment of s. pneumo?
vanc + cephalosporin
high dose therapy, IV route
resistance rising, esp penicillin
vaccines are capsule based
What is the microbiology of listeria monocytogenes?
gram+ non-spore forming rod, beta hemolytic
tumbling motility
grow in refrigerator, tolerate high salt concentrations, grow over wide range of pHs
What are the different diseases of l. monocytogenes?
diarrhea - most common, transient and undiagnosed, vomiting, epidemic gastroenteritis w fever
bacteremia
CNS inf - meningitis, meningoencephalitis, rhombencephalitis, cerebritis and brain abscess
What are the characteristics of neonatal listeriosis?
transplacental transmission
early onset (24h-6days) after birth
loss of appetite, lethargy, jaundice, vomiting, respiratory distress, shock, hypothermia
results in: abortion, stillbirth, premature birth
What is the epidemiology of l. monocytogenes?
lots of pregnant women - mild symptoms
wild and domestic animals, birds, soil, crustaceans, fish, oysters, flies, ticks
How is l. monocytogenes acquired?
food borne, not person to person - deli meats!
immunocompromised individuals at risk
pregnancy is biggest risk factor
What is the microbiology of N. meningitidis?
gram- diplo, optimal growth 35-37 degC
oxidase and catalase positive
require enriched CO2 for OPTIMAL growth
What are the antigens of N. meningitidis?
polysaccharide capsule, outer membrane proteins, LOS, pili
What is the epidemiology of N. meningitidis?
obligate human pathogen
aerosol transmission
serogroups important
Who does N. meningitidis affect?
all ages
most at risk: infants, young children, late teens
*What is the capsule structure of serogroup B of n. meningitidis?
*(alpha 2-8)-linked-N-acetyl-neuraminic acid
mimics human structures and is poorly immunogenic
What are the different diseases caused by n. meningitidis?
meningitis
meningitis w accompanying meningococcemia
meningococcemia w no evidence of meningitis
rarely pneumonia
dz peaks at 6 mos of age
look for purpuric rashes!
What are complications/sequelae of inf with N. meningitidis?
hearing loss
amputation
Waterhouse-friderichson syndrome
myocardial involvement
How does meningococcus enter and survive within the vasculature?
capsule and sialylated LOS reduce complement and Ab binding and phagocytosis
lymphocyte, endothelial and epithelial stimulation lead to cytokine release
How does the meningococcus penetrate the BBB and enter the meninges?
lipid microdomain formation and cytoskeletal rearrangements may enable bound bacteria to resist sheer stress
cytokine damage may increase bacterial transcytosis at all cell barriers
cytokine release following interxn of bacteria with leptomeninges causes meningitis
How is n. meningitidis diagnosed?
gram stain CSF
cultures CSF, blood (not throat)
molecular methods - PCR
How is n. meningitidis treated?
pen g
3rd gen cephalosporins
new quinolone resistance reported
How is n. meningitidis prevented?
vaccines
recently approved for children
none licensed in U.S. for serogroup B
eradication of carriage in close contacts: rifampin, cipro, ceftriaxone
