Neisseriae Flashcards
(25 cards)
Neisseria contains two important human pathogens:
- Neisseria meningitidis
- Neisseria gonorrhoeae
The Neisseria meningitidis mainly causes
Meningitis
meningococcemia
More about the Neisseriae
It’s a gram Negative
Kidney shaped
has a prominent polysaccharide capsule that enhances virulence by its
antiphagocytic action.
meningococcus
( the capsule also is the immunogen in the vaccine )
Meningococci are divided into at least 13 serologic groups on the
basis of
The antigenicity of their capsular polysaccharide
Five serotypes cause most cases of meningitis and
meningococcemia:
Serotype A: leading cause of epidemic meningitis
Serotype B: accounts for most diseases ( because it’s polysaccharide is not immunogenic in humans
and therefore is not part of the vaccines )
And also C , Y , W135
Neisseria gonorrhoeae polysaccharide capsule
It doesn’t have ANY
Gonococcus has multiple serotypes based on
The antigenicity of its PILUS PROTEIN
Neisseriae are oxidase-positive
This is an important laboratory diagnostic test in which colonies exposed to phenylenediamine turn purple or black as a result of oxidation of the reagent by the enzyme cytochrome c.
Neisseria meningitidis transmission
-Human are the only natural host
-And it transmitted through the airborne droplets
- they colonize the membranes of the nasopharynx and become part of the
transient flora of the upper respiratory tract.——-> and From the nasopharynx, the organism can enter the bloodstream and spread to specific sites, such as the meninges or joints
Two organisms cause more than 80% of cases of bacterial meningitis in infants older
than 2 months of age:
Strepococcus pneumonia And Neisseria meningitidis
Which of these organisms are most likely to cause epidemics of meningitis?
Group A of meningococci
ranks second to S. pneumoniae as a cause of meningitis
N. meningitidis
most common cause of meningitis in persons between the ages of 2 and 18 years.
N.meningitidis
Meningococci have four important virulence factors:
1- polysaccharide capsule
2-Endotoxin
3-IgA protease
4-Factor H binding protien FHBP
What factor of the meningcocci causes fever, shock, and other pathophysiologic changes?
EASYYYYY, Endotoxin
What factor of the meningococci enables the organism to resist phagocytosis by
polymorphonuclear leukocytes
Polysaccharide capsule
What does the immunoglobulin A (IgA) protease
Helps the bacteria attach to the membrane of the upper respiratory tract by cleaving secretory IgA
is the immunogen in the vaccine against group B meningococci
Factor H binding protein FHBP
The most severe form of meningococcemia is
Waterhouse–Friderichsen syndrome
which is characterized by:
high fever
shock
widespread purpura
disseminated intravascular coagulation
thrombocytopenia
adrenal insufficiency
The principal laboratory procedures are:
smear and culture of blood and spinal fluid samples
The differentiation between N. meningitidis and N. gonorrhoeae is made on
The basis of sugar fermentation
Meningcocci ferment Maltose but gonococci Do Not!
( Immunofluorescence can also be used to identify these species )
The procedure that can assist in the rapid diagnosis of meningococcal meningitis is the
“latex agglutination test” which detects capsular polysaccharide in the spinal fluid
-
What is the drug of choice for meningococcal infections?
Penicillin G or ceftriaxone
