Unit 3 - Bacterial Infection of CNS Flashcards
classic tetrad of meningitis?
headache
fever
photophobia
stiff neck
symptoms can be underwhelming sometimes
what does specifically pediatric meningitis look like?
- fever (cold hands, feet)
- refusing food, vomiting
- fretful, dislikes being handled
- pale, blotchy skin
- blank staring
- drowsy
- stiff neck
- high pitched
bacteriology of Neisseria meningitidis (meningococcus)
- human-restricted, encapsulated G- diplococci
- faculative intracellular
- ~13 serotypes
- oxidase+, catalase-
- ferments glucose and maltose, but NOT sucrose or lactose
- growth inhibited by trace metals and fatty acids, so must use chocolate agar instead of blood agar
what is oxidase testing?
a bacterial colony is lifted from nutrient media and smeared onto filter paper premoistened with oxidase reagent
describe the pathogenesis of meningogoccus if it doesn’t enter the bloodstream
- transmitted by airborne droplets
- use IgA protease to colonize nasopharynx (only reservoir)
- -spread and colonization may be enhanced by concomitant upper respiratory viral infections
- infection resolves without symptoms (controlled by IgG-enhanced complement, neutrophils –> lifelong immunity to infecting strain)
- -many have natural immunity by age 20, due to passive immunization from mother
describe the pathogenesis of meningogoccus if it enters the bloodstream
meningococcemia
-colonizes joints (septic arthritis) and meninges (meningitis, fatal if untreated, still may kill (80% of postinfant bacterial meningitis
what are the virulence factors of meningococci?
- deficiency in C6-9 predisposes to spread beyond respiratory system
- IgA protease cleaves IgA to reduce defense of mucus membrane
- polysaccharide capsule (primary virulence factor) resists phagocytosis
- endotoxin LOS (component of G- cell wall) may cause septic shock
what is the role of complement in Neisseria infections?
- required to prevent complications
- enhanced by Ab response
