Bacterial CNS infections

Question 1

The emergency department calls you at 2am. They have a 23 year old male that presented with high fever, nausea, stiff neck and is somewhat confused. They suspect bacterial meningitis and have performed a lumbar puncture. The micro lab closes at 11pm and so they are requesting that the on-call lab technologist come in to read the gram stain. What you do?

Answer 1

Start empirically on 3rd gen cephalosporin and vancomycin

Question 2

What are 3 important facts of bacterial CNS infections?

Answer 2

1) life-threatening with high mortality and morbidity
2) may be acute, sub-acute or chronic
3) the vulnerability of the CNS to effects of inflammation and edema mandates a prompt diagnosis with appropriate therapy to minimize consequences

Question 3

Name 4 examples of CNS infections

Answer 3

meningitis, enecephalitis, meningoencephalitis, brain abscesses

Question 4

what are the 4 goals in management of a patient with an acute CNS infection?

Answer 4

1) prompt recognition of a patient with a CNS infection
2) rapid initiation of appropriate empiric therapy
3) rapid ID of etiologic agent, adjusting therapy as needed
4) optimize management of complicating features

Question 5

Describe bacterial meningitis and its difference from aseptic meningitis

Answer 5

AKA purulent meningitis, potentially life threatening, symptoms include: fever, headache and an altered mental status, it is most commonly caused by pneumococcus. Aseptic meningitis a non-bacterial meningitis

Question 6

Describe the four stages of pathogenesis of a meningococcal infection

Answer 6

1) nasopharyngeal colonization 2) invasion of the epithelium 3) invasion of the blood 4) dissemination into cerebrospinal fluid

Question 7

What are 4 main causes of meningitis?

Answer 7

Pathogenic (bacterial, viral or fungal), inflammatory disease, cancer, head/spine trauma

Question 8

what are the 4 key characteristics of viral meningitis?

Answer 8

generally benign and rarely fatal, caused by enterovirus 80% of the time, generally clears in 3-8 days, HSV can cause a rare but serious infection requiring systemic antivirals

Question 9

What 4 bugs are most commonly found in bacterial meningitis in people under 3 months?

Answer 9

Group B strep, L. monocytogenes, E. coli, S. pneumoniae

Question 10

What 3 bugs are most commonly found in bacterial meningitis in people 3 months to 18 years?

Answer 10

N. meningitidis, S. pneumoniae, H. influenzae

Question 11

What 3 bugs are most commonly found in bacterial meningitis in people 18 to 50 years?

Answer 11

S. pneumoniae, N. meningitidis, H. influenzae

Question 12

What 3 bugs are most commonly found in bacterial meningitis in people >50 years?

Answer 12

S. pneumoniae, L. monocytogenes, gram negative bacilli

Question 13

Describe the main differences in symptoms between viral and bacterial meningitis?

Answer 13

Viral: person is alter and oriented
Bacterial: altered mental status characterized by confusion, combativeness, lethary etc. , low grade fever, stiff neck, photophobia

Question 14

What is the general approach to someone with suspected meningitis?

Answer 14

Decision making must occur within 1-2 hours. Analyze CSF with smears/stains, antigen screens to create a CSF profile

Question 15

What is the best method for the diagnosis of meningitis? What are the 2 advantages of this method?

Answer 15

Lumbar puncture: collects CSF, permits urgent distinction of bacterial from viral meningitis and a precise diagnosis

Question 16

What is the typical CSF profile of someone with bacterial meningitis?

Answer 16

Presence of neutrophils, up 10x higher protein concentrations, low glucose levels due to impaired sugar transport

Question 17

What is the typical CSF profile of someone with viral meningitis?

Answer 17

Presence of lymphocytes, 2-3x higher protein concentrations, normal glucose levels

Question 18

What are the key morphological, clinical and metabolic characteristics of Neisseria meningitidis species?

Answer 18

A gram negative, aerobic diplococcus with a polysaccharide capsule. There are 13 serogroups based on the different types of capsule. They often appear intracellular on a gram stain. Positive for catalase and oxidase. Grows on blood and chocolate agar. Ferments glucose and maltose.

Question 19

How does transmission of bacterial meningitis occur?

Answer 19

Between humans only, usually by saliva or aerosols. 10-30% of the time can be from asymptomatic carriers colonized in the nasopharynx. Incubation can take 2-10 days

Question 20

What three types of vaccines are used to prevent N. meningitidis infection?

Answer 20

1) monovalent serogroup C
2) monovalent serogroup B
3) quadrivalent serogroups A, C, Y, W-135

Question 21

What are the key characteristics of Listeria monocytogenes?

Answer 21

A gram positive bacilli. Catalase and CAMP positive. Exhibits tumbling motility at 25 degress and umbrella motility in a semi soft agar. Beta-haemolytic.

Question 22

Name and describe the most important virulence factor of Listeria monocytogenes

Answer 22

Listeriolysin O. Causes beta haemolysis of erythrocytes and destruction of phagocytes. Aids in escape from the phagosome

Question 23

How do you manage and treat suspected bacterial meningitis?

Answer 23

If possible, obtain CSF via lumbar puncture before starting antibiotics. Treat empirically with a 3rd generation cephalosporin and vancomycin. Add ampicillin if they are at risk for a Listeria infection