Micro U3 L1. Flashcards
Neisseria meningitidis bacteriology
gram - diplococci, encapsulated, oxidase +, catalase +, ferments glucose and maltose, grows on choclate agar or Thayer-Martin, facultative intracellular
What is the difference between chocolate agar and Thayer-Martin?
chocolate agar is for sterile and Thayer-Martin might have normal flora
What are the virulence factors for neisseria meningitidis
- IgA protease to colonize nasopharnyx 2. encapsulated 3. endotoxin LOS
How is neisseria meningitidis transmitted?
airborne droplets
What are differences between neisseria meningitidis and gonorrhea?
gonorrhea not encapsulated and needs close contact to be transmitted
What deficiency predisposes spread of neisseria meningitidis beyond respiratory system?
deficiency in late-acting complement C5-C9
Where does neisseria meningitidis colonize?
joints (septic arthritis) and meninges
Where is neisseria meningitidis typically found?
young adults living in close quarters (age 2-18) - natural immunity typically by age 20
Symptoms of meningitis in adults
classic fever/headache, stiff neck, photophobia
Symptoms of meningitis in children
irritiability, convulsions, lassitude, fever, abdominal discomfort/vomiting
How is diagnosis of neisseria meningitidis made?
draw CSF for meningitis; draw joint fluid for septic arthritis
Prevention of neisseria meningitidis
vaccine - Ab to capsule is protective
Meningococcemia symptoms
fever and hourly-spreading rash
Waterhouse-Friedrichen syndrome
high fever, shock, widespread purpura, DIC, thrombocytopenia, destruction of adrenal glands, 50% fatal
Labs for meningococcemia
gram stain, culture on chocolate agar, blood tests for DIC
Treatment for meningococcemia
penicillin G - NO STEROIDS
Prevention of meningococcemia
vaccine and antibiotic prophylaxis for close contacts
GBS bacteriology
gram + cocci, beta-hemolytic, encapsulated, polysaccharide toxin virulence factor, serotype-specific antibody-mediated immunity, normal vaginal flor (15-45%)
Pathogenesis GBS
most common cause of neonatal sepsis
Early disease vs Late disease neonatal sepsis
early disease: pneumonia w/ bacteria, 1-7 days postpartum, more common in US. late disease: bacteremia with meningitis, 1-12 wk postpartum, serotype 3
What are risk factors for neonatal sepsis?
prematurity and prolonged rupture of membranes
What are the predisposing risk factors for GBS disease in geriatrics?
diabetes, malignancy, CHF
Diagnosis of GBS
gram stain and culture, CT/MRI for abscesses, echocardiogram for endocarditis
Treatment for GBS
penicillin or amoxicillin (vancomycin if allergic) - sometimes surgical intervention needed esp in geriatric
Prevention of GBS
test term-pregnant patients - if positive then intrapartum IV administration of penicillin during delivery
CAMP Test for GBS
The CAMP test is a test to identify Group B β-streptococci based on their formation of a substance (CAMP factor) that enlarges the area of hemolysis formed by β-hemolysin from Staphylococcus aureus
Pneumococcus
strep pneumoniae, gram +, catalase -, facultative anaerobe, form diplococci in chain
What is the most common cause of community-acquired pneumonia, bacterial meningitis, bacteremia, and otitis media?
pneumococcus
What are the virulence factors for pneumococcus?
- encapsulated 2. IgA protease
What do pathogenic strains of pneumococcus produce?
pneumolysin
What is protective against pneumococcus?
anti-caupsule IgG
What unless most of the clinical disease symptoms in pneumococcus?
strong inflammatory response
When are the infection peaks for pneumococcus?
fall and winter (carriers congregate more closely)
Pathogenesis pneumococcus
easily colonizes upper respiratory tract using adhesion virulence factors - contained by innate immunity in healthy adults - can spread in young children, patients with pre-existing asthma, allergies, bronchitis, smoking, COPD
Exam for pneumococcus
diseases of direct extension (non-invasive) - sinusitis, otitis media, bronchitis, pneumonia. diseases of hematogenous spread (invasive) - meningitis, septic arthritis, pericarditis, endocarditis, osteomyelitis (bimodal distribution)
What is shown on radiology findings of pneumococcus
lobar consolidation
Signs of meningitis with pneumococcus
FAST (hours/days) - mental status changes, lethargy, delirium, + Brudzinski, cranial nerve palsies, focal neurologic defects
What are you looking for on spinal tap for bacterial meningitis?
decreased glucose, elevated lactic acid (fermenting), gram stain and culture are positive (unless antibiotic treatment was begun more than 4 hours before tap)
Treatment for pneumococcus
noninvasive: outpatient amoxicillin or cephalosporin invasive: admit with vancomycin plus ceftriaxome or cefotaxime
Pneumococcus antibiotic resistance
increase in dosage can sometimes overcome resistance but has a transposon so resistance to multiple antibiotics
Prevention of pneumococcus
Prevnar7 vaccine - raises protective IgG against the capsules in 7 serotypes (universal childhood vaccine). Prevnar 13 has protection for an additional 6 serotypes
