Flashcards in Micro 3 Deck (208)
What are common causes of meningitis in neonates?
Group B strep
What are common causes of meningitis in post-neonatal life?
Cause of chronic meningitis?
Causes of bacterial encephalitis?
Borrelia burgdorferi (Lyme Disease)
3 ways that microbes can penetrate the BBB
1. infection of the cells that comprise the barrier
2. passive transport through cells in vacuoles
3. carraige in WBCs
Why might steroidal anti-inflammatories be use in the treatment of meningitis?
Dampen the immune response
Decrease infiltration of PMNs, macrophages and pathogens
WBCs -> cytokines -> inflammation, edema, additional WBC recruitment
inflamation and edema are conducive to infiltration (diapedesis)
What are symptoms of meningitis?
high fever, sever and persistent stiff neck, photophobia, N/V
Changes in behavior: confusion, sleepiness, difficulty in waking (indicative of need for emergency treatment)
Infant: irritability, tiredness, poor feeding, fever, *bulging fontanel*
meningitis causing, gram +, catalase -, a-hemolytic, optochin sensitive
S.pneumo - most common cause of meningitis in US
Is there a vaccine for S.pneumo?
23-valent: capsular PS from strains responsible for 90% of infections
7-valent: capsular PS from strains responsible for infections in children, immunocompromised, elderly
What is the leading cause of bacterial meningitis in US?
What is second?
What are the most common capsular serotypes of meningitis causing N.meningitidis and what are the relative frequencies:?
In addition to typical meningitis symptoms, what may be seen in patients w/ N.meningitidis meningitis?
Hemorrhagic rash often w/ petechiae - reflective of assoc. septicemia
-1/3 of instances rash is fulminating w/ complications due to disseminated intravascular coagulation (DIC), endotoxemia, shock, renal failure
-DIC may -> gangrene / necrosis in extremities
What does H.influenzae require for growth?
Factors X: NAD and V: hemin
What organisms are typically responsible for outbreaks at universities?
Risks: poor diet, behavioral changes (ETOH consumption, smoking), pulmonary infections -> changes in immune function and microbiota composition
Some schools -> vaccination program
What is the fatality rate of neonatal meningitis?
How do survivors do?
1/3 of cases fatal
Survivors: often long-term sequelae: cerebral palsy, epilepsy, mental retardation, hydrocephalus
What organism causes Lyme Disease?
Disseminated disease can -> bacterial encephalitis
What is Guillan Barre Syndrome and what causes it?
Caused by Campylobacter jejuni
Disease is result of cross-reaction between bacterial ganglioside-like epitopes in LPS and Schwann cell myelin Ags
Immunologic attack ->Demyelination
How is a brain abscess diagnosed?
CT scan recommended before lumbar puncture
Characteristic ring-enhancing lesion w/ contrast is diagnosis
-fibrous capsule forms w/in 4-5 days of infection
Symptoms of brain abscess
headache, confusion, drowsiness, hemiparesis, seizures, fever
*usually no stiff neck*
What organisms are most often isolated from a brain abscess?
Gram +: Streptococcus (anginosis, milleri), Peptostreptococcus, Staphylococcus, Nocardia, Actinomyces
Gram -: Prevotella, Fusobacterium, Bacteroides, E.coli, Citrobacter koseri, P.mirabilis
AIDS pts: cryptococcus, toxoplasma
Almost always polymicrobial. Strep most common - synergy w/ gram negs
What often cause chronic meningoencephalitis?
What are the functions of bacterial capsules in CNS infection?
Prevent phagocytosis, Ab binding, complement activation
Toxicity to host cells
What is and what causes Valley Fever?
Fungal infection beginning in the lungs 7-21 days post infection
Typically clears quickly, but can disseminate to meninges, bones, joints, subcutaneous and cutaneous tissues
25% of disseminated cases -> meningitis (1% of total cases)
Initially flu-like, then symptoms of meningitis
Fatal if not treated.
Caused by Coccidiodes imitis (Fungus)
Risk: dust storms, earthquakes, excavation
What is Chagas Disease?
Caused by Trypanosoma cruzi - parasite carried by Triatome bugs
Initial sore at site of bite followed by fever and acute encephalitis
Chronic disease may have heart, colon, and nervous system manifestations
Where is Trypanosoma cruzi endemic?
Southern US - Southern Argentina
What is the CNS manifestation of malaria?
If malaria left untreated, infection can travel to brain causing lesions, coma and rapid death (24-72 hours)
Acute, widespread brain disease w/ fever
Greatest risk <10 years of age
5 genra of picornoviruses and associated diseases
1. Enterovirus (Polio, Coxsackie A and B, Echo) - diseases of alimentary (GI) tract
2. Rhino - cold - naspharyngeal
3. Cardiovirus - murine encephalomycarditis
4. Apthovirus - Foot + Mouth disease (cloven footed animals)
5. Hepatovirus - Hepatitis A
Properties of Cardio, Hepato and Entero viruses
Resistant to low pH, grow at 37C
Fecal-oral transmission, GI is site of primary infection
CNS infection results - paralysis and encephalitis
General properties of Aptho and Rhino viruses
Labile at low pH, grow at 33C
Aerosol transmission - Upper Respiratory Tract is site of infection