Exam #7: Bacterial Infections of the CNS Flashcards Preview

Microbiology > Exam #7: Bacterial Infections of the CNS > Flashcards

Flashcards in Exam #7: Bacterial Infections of the CNS Deck (74):
1

What are the two categories that CNS infections are divided into?

Meningitis= infections of the meninges

Encephalitis= infections of the brain parenchyma itself

2

What must microbes disrupt to gain access to the CNS?

BBB

3

What is hematogenous spread?

Spread through the bloodstream e.g. bacteremia

4

What are the different modes of entry to the CNS?

1) Hematogenous spread
2) Spread from an adjacent site
3) Direct inoculation (rare)
4) Neuronal spread e.g. HSV

5

What is acute pyogenic meningitis?

Bacterial meningitis that leads to the proliferation of neutrophils

6

What is aseptic meningitis?

Viral meningitis (historical term, meningeal inflammation without growth on culture)

7

How does bacterial meningitis compare to viral meningitis?

Bacterial is generally more severe

8

Who is predisposed to get meningitis?

Pneumococcal meningitis:
- Pneumonia & chronic OM

Meningococcal meningitis:
- 10-20 % population are carriers
- History of recent UTI-->easier to get into the CNS
- MAC (terminal) Complement deficiencies
- Outbreaks are most common in winter

Generally, individuals with altered or underdeveloped immune status are at an increased risk of developing bacterial meningitis

9

What are the common virulence factors associated with bacterial pathogens that cause CNS infections?

- Capsules= anti-phagocytic
- Fimbriae, pilli, & outer membrane= function in attachment & colonization

10

Describe the general pathophysiology of meningitis.

1) Bacterial penetration of the BBB

2) Inflammatory reaction*
- Many of the clinical manifestations are a result of the immune response in the confined area of the brain

3) Cell wall & toxin components of bacteria exacerbate the inflammatory response
- IL-1 & TNF-a -->ICP, Altered cerebral blood flow, Cerebral edema

11

What symptoms are characteristic of meningitis?

Fever
Headache
Stiff neck (nuchal rigidity)

- AMS

12

What CSF abnormalities are associated with bacterial meningitis?

*Presence of PMNs
Decreased glucose
Increased protein
Increased pressure

13

What CSF abnormalities are associated with viral meningitis & encephalitis?

Mono/lympho
*Rare PMN
Normal glucose
Normal or slight increased protein & pressure

14

What is the approach to empirical treatment of suspected CNS infection?

1) Empirical abx therapy is generally initiated
2) Age, predisposing factors, and other symptoms may provide clues
3) Examination of CSF & results should direct treatment plan

15

Who is most commonly infected with bacterial meningitis?

Infants & children

16

What are the MOST common etiological agents that cause bacterial meningitis in children?

Listen in order:

S. pneumoniae
N. meningitides
Group B step.
Listeria monocytogenes
Haemophilus influenzae

17

What is the most common cause of bacterial meningitis in neonates (<1 month)?

Group B Strep (S. agalacticae)

Note that this is especially common in kids that are less than 2 months old

18

What pathogen becomes increasingly prevalent in the teenage years?

N. meningitidis

19

What pathogen becomes more prevalent in the very young & old?

Listeria monocytogenes

20

List the characteristics of S. pneumoniae.

Gram positive coccus
Catalase neg
Chains
Diplococci
Oval
a-hemolytic
Optochin sensitive

*Capsulated*

21

What is the most common cause of vaccine preventable death in the US?

Pneumococcal disease

22

What clinical syndromes may pneumococcal meningitis follow?

Pneumonia
OM

23

List the virulence factors associated with S. pneumoniae.

Capsule
Pneumolysin= kills WBC
IgA protease

24

Describe the course of pneumococcal meningitis infection.

Acute onset
High mortality
Neurological sequela

25

How is pneumococcal meningitis diagnosed?

Clinically

- Gram stain CSF
- Latex agglutination
- Standard culture....etc.

26

How is pneumococcal meningitis treated?

*Medical emergency, begin empirical abx therapy with vancomycin & a cephalosporin*

27

How is pneumococcal meningitis prevented?

Vaccination; however, note that there are 90 different capsular polysaccharides
- Not ALL are covered
- However, currently we have a varieties of polysaccharide vaccines

28

What is PPV23 & what is the problem with PPV23?

This is the 23 valent vaccine for S. pneumonia that came out in the 1980s--DOESN'T work well in young kids

29

What are the current vaccine recommendations for S. pneumoniae

- Recommended for kids >2 with chronic illness, immunosuppression, & other risk factors
- Also recommended for adults >65

30

What is PCV13?

Pneumococcal polysaccharide conjugated nontoxic diptheria toxin
- 13 serotypes

31

List the characteristics of Neisseria meningitidis.

Gram - diplococcus
Kidney bean appearance
Oxidase positive
Catalase positive
Capsule
LOS

32

How does LOS differ from LPS?

- Shorter side chains
- No repeating polysaccharide

33

How is Neisseria meningitis cultured?

CO2 supplementation

34

What infections does Neisseria meningitis cause?

Meningitis
Bacteremia
Pneumonia
Arthritis
OM
Epiglotittis

35

How is Neisseria meningitis transmitted?

Aerosolized droplets

36

What are the clinical features of Neisseria meningitis infection? How does meningcococcal meningitis differ from pneumococcal meningitis?

Neisseria meningitis presents as:
- Abrupt onset fever
- Headache
- Neck pain
i.e. as typical meningitis

However, meningococcal meningitits also is accompanied by:
*Rash
- hypotension
- multi-organ failure

37

What causes the rash seen in Neisseria meningitis infection?

Antibody complexes

38

How is Neisseria meningitis treated?

Vancomycin and/or a cephalosporin followed by once N. meningitidis is identified PCN

39

How is meningococcal meningitis prevented?

Vaccination

Serotypes A, C, Y, W-135, BUT NOT B

40

What serotype causes half of the meningococcal meningitis causes in children under 2? Is there a vaccine for this strain?

- Serotype B
- No

41

How is meningococcal meningitis diagnosed?

- Recognize clinical signs & symptoms
- Gram stain CSF
- Rapid antigen detection in CSF

42

Describe the current meningococcal vaccine that is used in clinical practice.

"MCV4" -Meningococcal Conjugate Vaccine

Tetravalent polysaccharide conjugate vaccine

43

List the characteristics of Streptococcus agalactiae.

Gram + cocci
Chains
Catalase negative
B-hemolytic
Group B

44

What patient population is most susceptible to GBS meningitis?

Newborns

45

What other infections are caused by GBS?

Sepsis
UTI
Soft tissue infections

46

Why is the neonate susceptible to GBS infection?

- 10-30% of pregnant women are colonized by GBS
- Thus, maternal intrapartum GBS colonization is a MAJOR risk factor for the development of early onset disease in infants

*Note that maternal colonization increases risk of infection x25

47

What virulence factors are associated with GBS?

Polysaccharide capsule

48

Aside from maternal GBS colonization, what else increases the risk of GBS meningitis in the neonate?

- Obstetric issue
- GBS bacteuria
- Previous infant with GBS infection
- African American
- Low GBS antibody

49

What are the characteristics of early onset GBS disease?

Early onset= within the first week of life

Disease is characterized by bacteremia, pneumonia, & meningitis
- Respiratory distress
- Labored breathing
- Fever
- Lethargy
- Irritability

*Note that 1/4 that survive will suffer from permanent neurological sequela

50

What are the characteristics of late onset GBS disease?

Late onset= between 1-3 weeks after birth

Similar signs and symptoms of "early onset," but meningitis is more common

51

How is GBS diagnosed in the neonate?

- Recognition of clinical signs and the identification of the organisms--FEVER in NEONATE is a BIG DEAL
- Identification of organism in CSF
- Serologic confirmation by presence of Group B antigen

52

How is GBS treated?

PCN

53

How is neonatal GBS prevented?

- Universal screening of all pregnant women
- Intrapartum antibiotics i.e. high doses of IV PCN ~4 hours prior to delivery

*Note that there is no vaccine to prevent GBS

54

List the characteristics of Haemophilus influenzae type B.

Gram negative rod
Requires X & V
Chocolate agar
Encapsulated

55

What serotype of Haemophilus influenzae causes meningitis?

Type B

56

Is there a vaccine for HiB?

Yes, (conjugated) vaccine against the poly-ribitol phosphate (PRP) capsule

57

What diseases are caused by non-encapsulated Haemophilus influenzae?

Pinkeye
OM
Sinusitis

58

What diseases are caused by encapsulated Haemophilus influenzae?

Meningitis
Epiglottitis

59

What is the major neurological sequelae from HiB meningitis?

Hearing loss

60

How is HiB diagnosed?

Gram stain CSF
Latex agglutination test

61

How is HiB treated?

Similar to other forms of bacterial meningitis--broad to narrow spectrum

62

List the characteristics of Clostridium tetani.

- Gram + rod
- Anaerobic
- Spore forming--soil & feces
- Neurotoxin--tetanospasmin

63

Describe the typical entrance mechanism of Clostridium tetani.

- Spores enter through wound contamination or traumatic inoculation
- Umbilical stump can be contaminated in neonatal tetanus

64

What is tetanospasmin? Describe the mechanism of action.

- AB tetanus toxin

- B binds to motor neurons via polysaialoganglioside receptors
- Entire toxin is internalized & retrogradely transported to the spinal cord
- In the spinal cord, it activates the release of GABA
- Leads to "SPASTIC PARALYSIS"

65

What are the symptoms of tetanus?

Descending pattern of symptoms as follows:

"Lock jaw"
Neck stiffness
Difficulty swallowing
Muscle rigidity

66

How is Tetanus diagnosed?

Mostly based on clinical presentation & exposure history

67

How is Tetanus treated?

Passive & active immunization
- Administer Ig
- Vaccinate with inactivated tetanus toxin

68

How is Tetanus prevented?

Vaccination with tetanus toxoid--the "T' in DTaP

*formalin inactivated tetanus toxin*

69

List the characteristics of Clostridium botulinum.

Gram positive rod
Anaerobic
Spore forming
Produce neurotoxin

70

What is Infant Botulism?

"Floppy baby" Sydrome
- Infants ingest honey containing spores & produce toxin
- Most common cause of Botulism in the US

71

List the characteristics of Listeria monocytogenes.

Gram + rod
Motile

72

What is Listeria monocytogenes associated with?

Consumption of contaminated food i.e. deli meat, milk, cheese, poultry

*Transplacental transmission to neonate

73

How does Mycobacterium tuberculosis compare to other bacterial meningitis infections? What diseases can it cause?

Chronic symptom onset

- Meningitis
- Brain abscess

74

What CNS infections can S. aureus cause?

Meningitis
Brain abscess

Decks in Microbiology Class (49):