Term
| what are the symptoms of meningitis? |
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Definition
| fever, h/a, n/v, stiff neck, confusion/disorientation, and loss of consciousness (last 2 more common w/bacterial) |
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Term
| what are the consequences of a bacterial infection in the CNS? |
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Definition
| 1) influx of PMNs = inflammation = increased BBB permeability, leakage of serum into the CSF, and increased protein in the CSF. 2) edema = increased intracranial pressure. 3) altered glucose transport = decreased glucose in the CSF relative to serum. |
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Term
| what does the CSF analysis consist of for meningitis? |
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Definition
| evaluation of cells (#, type), glucose (CSF glucose is usually 2/3 serum levels), and protein |
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Term
| what does a CSF analysis for a viral CNS infection show? |
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Definition
| lymphocytes (but PMNs initially), normal glucose, and moderately increased protein (<150 mg/dL) |
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Term
| what does a CSF analysis for a bacterial CNS infection show? |
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Definition
| PMNs, low glucose (<25 mg/dL), and elevated protein (150-1000 mg/dL) |
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Term
| what does a CSF analysis for a chronic (TB+mycoses) CNS infection show? |
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Definition
| lymphocytes, low glucose, moderately increased protein (80-500 mg/dL) |
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Term
| what are the most common agents which cause acute bacterial meningitis |
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Definition
| streptococcus pneumoniae (pneumonia, otitis media), neisseria meningitidis (pharyngitis, rash), and haemophilus influenzae (otitis media). all 3 are non-pathogenic strains, part of the nasopharynx normal flora and may transiently colonize the nasopharynx. bacterial meningitis may follow a respiratory infection (otitis media, sinusitis, pharyngitis, pneumonia) which causes a bacteremia, which spreads to the CSF (through choroid plexus or between the cerebral capillary endothelial cells). |
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Term
| what virulence factors do n. meningitidis and h. influenzae have? |
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Definition
| capsule, IgA protease, pili, endotoxin (both are gram negative) |
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Term
| what virulence factors does s. pneumoniae have? |
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Definition
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Term
| what characterizes capsules as virulence factors? |
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Definition
| children do not generate an effective Ab response to polysaccharide Ag until they are 2-3 y/o (Ab to capsular Ag are protective, but no polysaccharide Ag = no opsonization). the sialic acid residues inhibit activation of complement - avoids complement mediated killing/opsonization. |
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Term
| what characterizes the capsules found on n. meningitidis? |
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Definition
| polysaccharide, serotypes: A,B,C,Y, W-135, vaccine: quadrivalent for A,C,Y, W-135 (**not type B). |
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Term
| what characterizes the capsules found on h. influenzae? |
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Definition
| polysaccharide, serotype: b, vaccine: Hib |
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Term
| what characterizes the capsules found on s. pneumoniae? |
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Definition
| polysaccharide, many serotypes, vaccine: pneumovax (23 valent) |
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Term
| what characterizes the capsules found on group B strep? |
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Definition
| polysaccharide rich in sialic acid, serotype: III in neonatal meningitis |
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Term
| what characterizes the capsules found on e. coli? |
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Definition
| polysaccharide rich in sialic acid, serotype: K1 in neonatal meningitis |
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Term
| what characterizes dx of bacterial meningitis? |
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Definition
| can be fatal if untreated, need to start antibx asap then confirm dx: blood+CSF for cx and gram stain. h. influenzae needs to be grown on blood agar/chocolate agar. **obtain cx before starting antibx. gram stain of CSF sediment is both sensitive and specific, but that of the blood is often negative b/c titers are too low. protein + glucose levels should be measured in the CSF. latex agglutination tests for CSF supernate can ID the serotype of the pathogen (even if cx results are negative). |
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Term
| what is the chocolate agar plate/blood agar plate result for n. meningitis? |
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Definition
| CAP+, BAP+, gram negative diplococci |
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Term
| what is the chocolate agar plate/blood agar plate result for s. pneumoniae? |
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Definition
| CAP+, BAP+, gram positive diplococci |
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Term
| what is the chocolate agar plate/blood agar plate result for h. influenzae? |
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Definition
| CAP+, BAP-, gram negative coccobacilli |
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Term
| what characterizes neisseria meningitidis biochemically? |
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Definition
| n. meningitidis is *oxidase positive, oxidizes *glucose and maltose in the cystine trypticase agar (CTA) test, will turn a phenol red indicator from red - yellow (acidic), and agglutination tests can determine serotype. the most common serotypes associated w/neisseria meningitidis are A,B,C,Y, W-135 - B and C of which are the most associated w/meningitis in the US (no vaccination for B [35% of deaths], Y = pneumonia, A = epidemics in asia/africa). |
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Term
| what characterizes transmission of neisseria meningitidis? |
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Definition
| neisseria meningitidis transiently colonizes the nasopharynx of healthy people (no animal reservoir, asymptomatic carriage) via respiratory droplets from asymptomatic carriers. this occurs more commonly in closed populations (schools, military). |
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Term
| who is at higher risk for meningitis due to neisseria meningitidis (essentially, who should be vaccinated)? |
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Definition
| children < 5 (however, vax recommended at 11-18), institutionalized pts, college students, pts w/late complement deficiencies (C5-C9), asplenic individuals, and pts who travel to areas where A+C serogroups are endemic. |
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Term
| who is a lower risk for meningitis due to neisseria meningitidis? |
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Definition
| pts who can produce Ab to the capsule (also other bacteria may have produced an effective cross-reactive Ab) |
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Term
| what characterizes the clinical disease due to neisseria meningitidis? |
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Definition
| *meningitis: abrupt onset of h/a, fever, stiff neck, n/v, photophobia, and altered mental status. in young children symptoms may be non-specific: fever+vomiting. *meningococcemia: lipid oligosaccharide (LOS - gram negative) triggers an inflammatory response which leads to vascular damage, shock, DIC, which may occur w/o meningitis and includes a rash on the trunk/lower extremities (may coalesce), bilateral destruction of the adrenal glands (waterhouse-friderichsen) and leads to a 25% mortality rate (even w/tx). meningitis may occur simultaneously w/meningococcemia - but this is less common. other clinical syndromes include pneumonia w/pharyngitis, arthritis, or urethritis. |
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Term
| what characterizes the MPSV4 or menomune neisseria meningitidis vaccine? |
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Definition
| first developed, covers serotypes A, C, Y and W135. poorly immunogenic in children <2. protection = 3-5 yrs. |
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Term
| what characterizes the MCV4 or menactra neisseria meningitidis vaccine? |
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Definition
| covers serotypes A, C, Y and W135. conjugated to diphtheria (more efficient/effective w/polysaccharide capsules). recommended for pts 11-55 y/o. **preferred vaccine for neisseria meningitidis** |
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Term
| what characterizes the MenACWY-CRM (menveo) neisseria meningitidis vaccine? |
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Definition
| basically the same as the MCV4/menactra - but less studies and therefore not recommended for younger pts. |
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Term
| what characterizes haemophilus influenzae biochemically? |
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Definition
| haemophilus influenzae: gram negative coccobacilli which requires X factor (hematin) and V factor (NAD) to be cultured on blood agar, but will grow on chocolate agar (also can grow in the vicinity of organism that can cause hemolysis). |
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Term
| what types of haemophilus influenzae cause disease? |
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Definition
| the nonencapsulated/typable strains are normal flora of the nasopharynx and are often associated w/sinusitis/otitis media. there are 6 serotypes of haemophilus influenzae, of which type b is the most virulent. the vaccine (Hib) was developed against this and now the serotypes c and f (along w/the nonencapsulated strains) are most common. |
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Term
| what characterizes clinical disease due to haemophilus influenzae? |
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Definition
| children (3-18 mos mostly affected): sinusitis, epiglottitis, and otitis media. adults (elderly/chronic pulmonary): pneumonia. meningitis usually follows a URI. less common now since vaccine. |
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Term
| what characterizes the vaccines available for haemophilus influenzae? |
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Definition
| the early Hib did not induce an Ab response in children less than 18 mos old, which wasn't very useful as this is the most susceptible population. the current Hib has the polyribosylribitol phosphate (PRP, Ag) conjugated to a protein and is either available as PRP-OMP or PRP-TT (booster is necessary though). |
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Term
| what characterizes streptococcus pneumoniae biochemically? |
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Definition
| this alpha hemolytic gram negative is susceptible to optochin (look for zone of inhibition around a P disc on a BAP). s. pneumoniae is soluble in bile salts (deoxycholate) and has multiple serotypes (23 valent vax). |
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Term
| what characterizes clinical disease due to strep pneumoniae? |
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Definition
| most common = pneumonia, sinusitis, otitis media - which if serious enough can lead to bacteremia crossing the BBB and causing meningitis. pts at risk for serious infections: elderly and compromised (esp asplenic) -> should be vaccinated. |
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Term
| what is the most common cause of neonatal meningitis? |
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Definition
| group B streptococci/s. agalactiae (beta hemolytic) which can colonize the genital tract and be transmitted to infants during birth (screen for GBS @ 35-37 wks). the serotypes are determined by the antigenicity of the polysaccharide capsule - w/serotype III most commonly associated w/meningitis. |
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Term
| what characterizes clinical disease due to group B streptococci/s. agalactiae? |
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Definition
| *early onset: <7 days via amniotic fluid/parturition = bacteremia, pneumonia, meningitis w/5% mortality and 15-30% blind/deaf/mentally retarded. risk factors: heavily colonized mother w/o specific Ab, premature rupture of the membranes, pre-term delivery, and prolonged labor/complications. *late onset: 1 wk-3 mos, usually nosocomial (lack of maternal Ab/dirty conditions) = bacteremia and meningitis. mortality is low and less severe neurological complications are possible. |
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Term
| what is the second most common cause of neonatal meningitis? |
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Definition
| e. coli, which occurs in infants < 1 mo, involves the K1 capsular Ag and can be present in the GI tract of the mother and infant. |
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Term
| what is the third most common cause of neonatal meningitis? |
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Definition
| listeria monocytogenes, a gram positive coccobacillus which is widespread in the GI tracts of animals. transmission = contaminated food (grows cold temperatures - dairy, sausage, deli meat), transplacental transmission (early onset neonatal disease), and transmission during birth (late onset neonatal disease). |
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Term
| what characterizes disease due to listeria monocytogenes? |
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Definition
| *early onset neonatal disease: granulomatous infantiseptica, disseminated abscesses/granulomas, high mortality rate. *late onset neonatal disease: 2-3 wks after birth, *meningitis or meningoencephalitis w/bacteremia. *adult: GI/mild flu-like symptoms may occur and bacteremia can disseminate to the CNS - pts at risk for this: immunocompromised pts (renal transplants/Ca) and infants w/late onset neonatal disease. |
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Term
| what characterizes cryptococcus neoformans as a cause of meningitis? |
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Definition
| cryptococcus neoformans, a yeast (not dimorphic) found worldwide in soil contaminated w/pigeon droppings is inhaled and may lead to a subclinical or mild-influenza-like pulmonary infection. disseminated disease involving the CNS occurs more commonly in AIDS pts (disease-defining) usually in the CNS, followed by the skin or bones. symptoms: h/a, fever, stiff neck, and disorientation - but slower onset than bacterial meningitis. |
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Term
| how is cryptococcus neoformans diagnosed? |
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Definition
| CSF cx grows in 3-4 days. india ink prep of CSF (clear zone appears around organism due to capsule) can be done, but requires > 10^5 organisms/mL. latex agglutination test: detects capsular Ag, more sensitive than india ink. |
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Term
| what are the 3 possible sources for brain abscess formation? dx? symptoms? |
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Definition
| hematogenous spread during bacteremia, spread from a sinus/dental/ear infection, and spread following head injury/sx. dx: CT/MRI. symptoms: seizures, progressive loss of consciousness, and focal deficits (depend on location). |
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Term
| what characterizes acute brain abscesses? chronic? |
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Definition
| *acute: mix of aerobes and anaerobic organisms including: staphylococci, anaerobic streptococci, and gram negative bacilli. *chronic: mycobacteria, fungal pathogens, and parasites. |
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Term
| what are the most pathogens associated w/brain abscesses in immunocompetent pts? |
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Definition
| strep (aerobic, anaerobic viridans - endocarditis), enterobacteriaceae (gram neg bacilli - proteus, e. coli, klebsiella), anaerobes (bacteroides, fusobacterium), and staph |
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Term
| what are the most pathogens associated w/brain abscesses in immunocompromised pts? |
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Definition
| nocardia, toxoplasma, aspergillus, candida, and cryptococcus neoformans |
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Term
| where characterizes hematogenous brain abscesses? |
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Definition
| usually multiple and found in the posterior frontal or parietal lobes |
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Term
| what brain absecesses may occur following head trauma? |
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Definition
| MRSA, staph epidermidis, enterobacteriaceae, and pseudomonas aeruginosa |
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Term
| what characterizes nocardia? |
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Definition
| this gram positive filamentous bacteria (appears like fungus/actinomyces) can cause pulmonary disease and may disseminate to the CNS (multifocal lesions) - nocardia asteroids is the most common spp associated w/this presentation. it may also cause a cutaneous lesion - n. brasiliensis. |
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