CNS Infections- N. meningitidis Flashcards
(37 cards)
The non-pathogenic species of Neisseria:
are normal flora of URT & other mucosal surfaces in the human body.
-Many nonpathogenic species are non-encapsulated variants of the encapsulated/disease-causing strains of N. meningitidis
Description of Neisseria meningitidis
aka meningococcus
- Gram-negative, kidney-bean shaped, diplococcus
- oxidase positive
- fastidious
Virulence Factors- All infectious meningococcus are encapsulated and are grouped based largely on ____________.
Important groups are ____________. Capsular polysaccharide is _________. Group-specific antibodies do not significantly cross-react.
the serological differences in capsular types
A, B, C, Y, W-135, X
antiphagocytic
Type B capsule of Neisseria and E. coli K1 capsule have the same chemical composition (sialic acid); sialic acid is a human self antigen, hence they ____________.
are poorly immunogenic
Neisseria possess ______ instead of LPS:
Lipooligosaccharide (LOS)
- consists of Lipid A (endotoxin) + extended core (no antigenic side chain).
- is antiphagocytic by molecular mimicry
- causes Disseminated Intravascular Coagulopathies (DIC) because contains lipid A
Major serogroups are B, C, Y. ______ causes ½ of all infection in the US.
Serogroup Y infected patients are more likely to be __________.
Serogroup B
older and manifest with pneumonia
Countries where meningococcal disease is hyperendemic or epidemic are __________.
In North America vs the rest of the world: Specific serogroups of meningococci are associated with ____________.
Africa and Middle Eastern countries
epidemics, which occur in cycles
Transmission is via _________
aerosols, respiratory droplets.
POE and initial site of colonization is the nasopharynx.
____ are the only reservoir for all Neisseria sp.
humans
Carriers are common in epidemics, but few develop disease; carriers are are largely responsible for spread of disease via aerosols
Age most commonly affected
Infants → Young adults (1 month → 22 y-o-age)
- infants and children (1 month → 24 months-o-age).
- older children/adolescents (6 → 19 y-o-age).
- young adults (19 → 22 y-o-age)
a. military recruits.
b. college students living in dorms.
Seasonality
Late fall → winter → early spring
Risk Factors for infection (lots)
- Close contact, crowding
- Susceptibility (lack of group-specific antibodies).
- Living in a college dormitory or basic training in the military (increased risk of exposure to new groups of meningococci)
- antecedent RT may predispose host to infection
- intimate kissing
- tobacco smoke exposure (direct or passive)
- bar patronage
- household crowding
- binge drinking
- low socioeconomic status
Susceptible populations
- Infants-Young adults (1 month → 22 y-of-age).
- Families (familial spread)
- Genetic predisposition to infection (properdin or complement deficiencies)
S/S for people aged 16 years or younger
- Early symptoms of sepsis occurred within 8 hours of infection (leg pains, cold hands and
- Late symptoms: meningism and impaired consciousness occur about 13 to 22 hours after onset of early symptoms
S/S for adults
- Early symptoms may occur and consist of only mild pharyngitis without exudate, slight fever, and headache at onset OR several days of flu-like symptoms with emesis.
- Then the classic symptoms of meningitis occur OR classic symptoms without early symptoms occur
Other S/S of Neisseria meningitidis for all age groups
Besides the classic clinical manifestations of meningitis:
-petechial (non-blanching, hemorrhagic) rash on ankles and wrist (first) then trunk, thigh, forearms may appear if septicemia also present
Patients may survive disease without or with significant sequelae, which include:
- nerve deafness
- CNS damage
- necrosis of large areas of skin or tissues often results in amputation
Waterhouse-Friderichsen syndrome (fulminant meningococcemia)
- circulatory shock due to SIRS → severe sepsis or septic shock.
- bilateral hemorrhagic necrosis of adrenals → low cortisol leves → hypotension.
- disseminated intravascular coagulation
- Waterhouse-Friderichsen syndrome is NOT limited to N. meningitidis; this disease is seen in certain other fulminant bacterial diseases.
Purpura Fulminans
AKA symmetrical peripheral gangrene (SPG) is meningococcemia +/- meningitis:
- hypothermia.
- seizures
- shock
- thrombocytopenia
- leukocytosis
- purpura: meningococcus IS IN the lesions
- highest mortality rate (15→50%) occurs with Group C disease, esp. in persons with purpura fulminans, even with appropriate treatment
- Purpura fulminans is NOT limited to N. meningitidis; this disease is seen in certain other fulminant bacterial diseases
Other meningococcal infections
- pneumonia or endocarditis
- meningococcemia may be seen without CNS localization
Lab tests
- Microscopic examination and culture of skin lesions (aspirant or biopsy). If petechial or purpuric lesions are present, Gram-stain of lesion biopsy will often (50% of the time) reveal meningococcus.
- Obtain nasopharyngeal cultures to screen for carriers, treat carriers with Rifampin
Determine antibiotic sensitivity – resistance to many drugs is documented; ____ requried.
MBC
When taking a nasopharyngeal culture to screen for carriers, the carriers must then be treated with
Rifampin
Treatment for Neisseria meningitidis
Antimicrobial therapy is ceftriaxone, or cefotaxime or penicillin G
(other treatment: : Bacteriocidal/permeability-increasing protein, recombinant rBPI)
