Lecture 2 - Neisseria meningitidis Flashcards
Describe what the bacteria is and its virulence factors
What is meningitis?
meningitis the inflammation of the meninges (membranes covering the brain and spinal cord for protection)
meningitis occurs when the Cerebral Spinal Fluid (fluid between two layers of the meninges) gets infected
What kind of bacteria is Neisseria meningitidis?
its a gram negative diplococcus [two round balls]
What are serotypes?
serotypes are a way to identify the type of meningitis strain
- is the arrangements of carbohydrates on the bacteria’s capsule [polysaccharides and sugars]
What are capsules?
it is a virulence factor;
- a bacteria’s capsule is the polysaccharide layer of the bacteria which prevents white blood cells from easily finding it in the body [prevents phagocytosis]
How many serotypes of N.meningitidis are there? which ones are responsible for most of the epidemics in the world?
theres over 12 serotypes but only 4 of them are responsible:
- serotype A [common in Africa]
- serotype B [common in america]
- serotype C [caused meningitis outbreak in edmonton]
- serotype W-135
How is N.meningitidis transmitted?
via droplet (coughing, sneezing, saliva) that ranges in 1m from the person (if you are more than 1m apart from the infected person, you should be in a safe non-transmission zone)
What are 3 virulence factors of N.meningitidis?
- invades mucosal membranes and then moves to the bloodstream or CSF or both
- outer membrane of the gram - bacteria contains an ENDOTOXIN called “Lipid A”
- contains a CAPSULE which evades phagocytosis by WBC
What are the factors that arise when endotoxin (lipid A)is released from N.meningitidis?
ONLY IN GRAM - BACTERIA
Lipid A [lipo-oligopolysaccharide] causes inflammation in our bodies, which then activates blood clotting mechanisms which leads to:
- DIC (disseminated intravascular coagulation)
- Hemorrhages called petichiae and purpura [petichiae are tiny hemorrhages of the skin & purpura are large hemorrhages]
- shock
what is a nickname of Neisseria meningitidis (not scientific)?
meningococcus singular
or
meningococci plural
What is meningococcal meningitis?
inflammation or infection of the meninges
- occurs when bacteria gets into the CSF in the meninges and starts replicating; the body sends inflammatory cells (WBCs) to the CSF which increases the pressure in the brain
what is meningococcal sepsis?
replication of bacteria in the blood stream
- DISSEMINATED DISEASE (its spread beyond its origin area and diffused into other areas like the blood)
- occurs quickly and causes intravascular coagulation (clotting) and can lead to amputation
what is the survival rate of meningitis?
90-95% IF DIAGNOSED EARLY AND TREATED EARLY
What are 7 symptoms of meningitis [meningococcal meningitis] ?
- headache
- stiff neck
- nausea
- sore throat
- coma
- petichiae (small hemorrhages on the surface of the skin)
- photosensitivity
What are 5 symptoms of sepsis [meningococcal sepsis]?
- fever
- petrichiae/purpura
- shock
- hemorrhage
- DIC (disseminated intravascular coagulation] leading to internal organ meltdown
What are the 5 steps for diagnosing meningitis?
- take CSF or blood sample from patient [prior to admitting antibiotics]
- gram stain the sample and report it to the physician
- culture (grow the bacteria) in the lab & run PCR
- run antibiotic susceptibility tests (to make sure the right antibiotic will target the bacterial serogroup)
- report the serogroup for epidemology (to prevent the spread in the public)
What are the treatment guidelines for meningitis?
- has to be immediate
1. antibiotics must be administered right after taking blood/csf sample
2. empirical antibiotic treatment must be used initially –> this is the physicians best guess before the bacterial culture is confirmed in the lab [this is usually third generation cefriaxone because it has good penetration of BBB]
3. antibiotic susceptibility tests done on all bacterial isolates
What is the epidemiology of meningitis?
Outbreak [unusual cluster of cases in a short time span] in North America
Endemic [in the population] in Africa
- most cases occur in temperate climates like winter time
Three types of vaccines to treat meningitis?
- polysaccharide –> made by injecting parts of the capsule to humans so they develop an immune response (make antibodies) to find and kill the bacteria
- Conjugated –> polysaccharide [capsule] combined with a protein thats good for children under 2 years of age OR immunospressed individuals who can’t make antibodies –> same thing, except the polysaccharide (capsule) is mixed with a protein and the immune system makes anitbodies of the protein
- Type B Vaccine –> based on proteins in the cell wall and NOT THE CAPSULE –> new vaccine and has a 50-60% success rate
6 public health measures for meningitis?
- rapid identification of disease
- rapid identification of contacts (friends and family of patients)
- administration of prophylactic antibiotics to those contacts (so they develop antibodies to the bacteria)
- Vaccination of susceptible individuals
- health prevention information to the surrounding public
- reportable disease [physicians MUST report cases of meningitis as a preventative measure]
