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NMSK-B II > Microbiology 2.4 > Flashcards

Microbiology 2.4 Flashcards

(45 cards)

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1
Q

How do pathogens enter the CNS?

A
  • hematogenous (transverse BBB)
  • peripheral nerves
  • olfactory neurons
  • local injury or congenital defect
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2
Q

What are the two barriers of the CNS?

A
  • blood brain barrier

- blood CNS barrier

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3
Q

What is Meningitis?

A

infection of the meninges after crossing blood-CSF barrier

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4
Q

What is Encephalitis?

A

infection of the cerebral cortex after crossing the BBB

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5
Q

What is Meningoencephalitis?

A

both meninges and cerebral cortex are infected

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6
Q

What is Myelitis?

A

infection of the spinal cord, usually by viruses

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7
Q

What is a brain abcess?

A

usually from a bacterial or fungal infection

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8
Q

What is postinfectious encephalitis?

A

usually 2-3 weeks after an infection elsewhere in the body, peripheral immune cells gain access to brain through BBB

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9
Q

How many species of bacteria are typically involved in acute bacterial meningitis?

A

one

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10
Q

How do CNS infections occur in terms of spread?

A

From the bloodstream, the bacteria settle in the large venous sinuses in the brain, then penetrate the dura and arachnoid, and infects the CSF

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11
Q

What is the clinical presentation of acute meningitis in children and adults?

A
  • fever
  • headache
  • nuchal rigidity
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12
Q

What are bacteria-specific manifestations of Streptococcus pneumoniae?

A
  • CSF nasal discharge

- Pneumonia

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13
Q

What are bacteria-specific manifestation of Neisseria meningitidis?

A
  • Non-blanching petechiae or purpura

- Endotoxic shock

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14
Q

What is the clinical presentation of acute meningitis in infants and neonates?

A
  • fever
  • lethargy
  • irritability
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15
Q

Neisseria meningitidis

A
  • Small, gram-negative diplococci
  • Aka, meningococcus
  • Facultative intracellular pathogen
  • Strictly a human pathogen
  • catalase +
  • oxidase +
  • ferments glucose, maltose
  • capsule*
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16
Q

What are the most important disease-producing serogroups of Neisseria meningitidis?

A 
A
C
B [not covered by vaccine]
W-135
Y
**from capsule**
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17
Q

What is the most common disease caused by N. meningitidis?

A

acute purulent meningitis

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18
Q

What are the main virulence factors of N. meningitidis?

A
  • polysaccharide capsule
  • IgA protease
  • pili and OMPs
  • LOS
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19
Q

How is N. meningitidis transmitted?

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A
  • large droplet
  • oral secretions
  • respiratory droplets
20
Q

What is the risk group for N. meningitidis?

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A
  • infants
  • adolescents
  • college students
  • military recruits
21
Q

How is N. meningitidis infection treated?

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A
  • cephalosporin

- treat those close to them once bug is confirmed

22
Q

What are the two kinds of vaccines available in the U.S. for meningococcals?

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A
  • Meningococcal polysaccharide vaccine
  • *no memory response
  • Meningococcal conjugate vaccine (better)
  • *memory response
23
Q

Streptococcus pneumoniae

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A
  • Gram-positive coccus
  • Usually diplococci or short chains
  • Facultative anaerobic
  • Encapsulated
  • catalase -
  • alpha-hemolytic (green)
  • Optochin-sensitive**
  • bile soluble (cells are lysed)*
  • capsule*
24
Q

What is the epidemiology of S. pneumoniae?

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A

more common during winter and in early spring

25
How is S. pneumoniae transmitted?
- usually autoinoculation | - not usually person-to-person [do not need post-antibiotics for family]
26
What are the main virulence factors of S. pneumoniae?
- polysaccharide capsule - IgA protease - pneumolysin***
27
What is pneymolysin?
A cholesterol-dependent cytolysin that creates pores in cholesterol-containing membranes, thus causing host cell lysis by S. pneymoniae
28
How is a pneumococcal meningitis diagnosis made?
- CSF isolation | - latex agglutination test
29
How is pneumococcal meningitis treated?
-vancomycin + ceftiazone | penicillin resistant
30
Streptococcus agalactiae
- Spherical, Gram-positive cocci in chains - Only species with group B Lancefield antigen = Group B streptococcus (GBS) - Bovine GBS strains can cause mastitis in dairy cows, so “agalactiae” meaning “no milk” - catalase - - Beta hemolytic - bacitracin-resistance - CAMP + - bippurate test + (purple)
31
Where does Streptococcus agalactiae colonize?
- lower Gi | - GU
32
What is the risk population for Streptococcus agalactiae infection?
- elderly - dabetic - pregnant women - babies
33
What are the risk factors for early onset neonatal GBS disease?
- Maternal colonization of GBS - Prolonged rupture of membranes - Preterm delivery - Intrapartum fever
34
What are the risk factors for late onset neonatal GBS disease?
- From an exogenous source (mother, other neonate, nurse) | - Prematurity
35
What are the virulence factors of S. agalactiae?
- polysaccharide capsule | - pili
36
How is GBS screened for?
Pregnant women should undergo vaginal-rectal screening for GBS colonization at 35-37 weeks gestation via culture based testing
37
Listeria monocytogenes
- Short, Gram-positive rods - Alone, in pairs or short chains - Non-spore forming - No capsule! - Can’t use morphology alone for diagnosis - weak beta-hemolytic - catalase + - CAMP +
38
How is Listeria monocytogenes distinguished from other Listeria species?
sugar fermentation
39
What is tumbling motility?
motility in broth on a slide at RT of Listeria monocytogenes
40
Where does Listeria monocytogenes culture?
- soil | - decayaing vegetable matter
41
What are common food sources for Listeria?
``` "foods in the fridge" -deli meat hot dogs -soft cheeses -unpasturized milk -smoked seafood -meat spread and pate -melon -cabbage ```
42
What are the virulence factors of Listeria monocytogenes?
- actin comets/tails (motility) * *avoids immune system - facultative intracellular - internalin - LLO - ActA
43
What is the risk groups of listeriosis?
- pregnant women - babies - immunodeficient - elderly * *most common in summer
44
How is listeriosis diagnosed?
- culture organism | - "tumbling motility" from CSF
45
What is the treatment for listeriosis?
pregnant women: ampicillin neonates and severe cases: gentamicin

NMSK-B II (15 decks)

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