Bacterial Meningitides Flashcards
(53 cards)
What are the 2 broad categories of CNS infections?
Meningitis- infection in the subarachnoid space
Encephalitis- infection in the parenchyma
What was the major cause of bacterial meningitis up until 1986?
Haemophilus Influenzae
What has been the major cause of bacterial meningitis since 1986?
Streptococcus pneumoniae
Why don’t we see as many cases of bacterial meningitis due to haemophilus influenzae?
A vaccine came out in 1986
How has the rate of bacterial meningitis due to Neisseria meningitidis changed over the years?
It hasn’t. It’s held steady
What is meant by an “aseptic” case of meningitis?
The doctor cultured the sample improperly, and nothing grew, so it looks like there was no bacteria. MISSED DIAGNOSIS
Which organisms usually cause community acquired bacterial menigitis?
The same ones that colonize the respiratory tract first before spreading to the CNS:
S. Pneumoniae
H. influenzae
N. Meningitidis
What groups of people get hospital acquired bacterial meningitis?
Patients who are the victims of an unclean procedure putting the bugs where they’re not supposed to be (dental work, catheters, LP)
Immunocompromised
What kinds of organisms cause hospital-acquired bacterial meningitis?
Gram negative rods
Staph aureus
Strep and staph
Why is inflammation bad when bacteria penetrate the BBB?
Because the inflammation increases the permeability of the BBB even more, causing serum to leak out and cause edema, increased intracranial pressure, and altered blood flow
******
What are the 3 pathways that pathogens can use to get into the CNS?
- Invasion of the bloodstream and seeding of the CNS*****most common
- Retrograde neuronal pathway- walks up nerves from nose to brain
- Direct contiguous spread from trauma, infections
What is the classic triad symptoms of bacterial meningitis?
Fever
Headache
Neck stiffness
Why would you draw a serum glucose and a CSF glucose if you suspected bacterial meningitis?
CSF glucose will be lower than serum glucose, since the bacteria have been eating it
What are the symptoms that your neonate baby is suffering from bacterial meningitis?
Bulging fontanelle
High pitched cry (nonstop scream)
Hypotonia
Paradoxic irritability (cries when held, quiet when stationary)
High fever (usually)
Hypothermia if brain gets too messed up
What are the 3 predominant agents of neonatal meningitis?
GI Pathogens:
Streptococcus agalactiae
E. Coli
Listeria monocytogenes
How does the CDC recommend we prevent neonatal meningitis?
Prenatal screening for vaginal/rectal colonization with Group B strep for all pregnant women at 35-37 weeks
Antibiotics for women who culture-positive (unless they’re having a C section or they already started going into labor/water broke
How do babies do after getting bacterial meningitis?
Up to 60% of them die
Survivors have permanent brain defects
What is the most common cause of neonatal bacterial meningitis?
Strep agalactiae
aka Group B Strep (GBS)
Where does Strep Agalactiae (GBS) live?
45% of people are carriers in their vagina, GI tract, and Upper Respiratory tract with no ill effect at all
If a mother has strep agalactiae colonization, will she give it to her baby at delivery?
50% of the time
Then 1-2% of colonized neonates develop infection
Strep agalctiae:
Gram:
Shape:
Gram positive
Cocci
What does strep agalactiae look like on blood agar?
Gray-white colonies with a narrow zone of B-hemolysis
B-hemolysis=fully lysing RBCs
Does strep agalactiae have many virulence factors?
Not really. Thats why it only makes neonates and AIDS patients sick
What is the difference between Early Onset vs Late Onset Neonatal Group B Strep Infections?
Early: problematic delivery led to infection. Symptoms develop within first 5 days of life.
Late: routine, smooth delivery. Symptoms develop 7 days to 3 months later.
