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IAHI Block 2 > Bacterial CNS and STDs > Flashcards

Bacterial CNS and STDs Flashcards

1
Q

What 2 bacterial CNS infections are most prominent in Children (1mo - 15y)

A 
Neisseria meningitidis (25-40%)
Haemophilus influenzae (40-60%)
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2
Q

Structure of Neisseria meningitidis

A

Gram negative diplococci - Lipooligosaccharide (LOS instead of LPS)
Polysaccharide capsule
Possesses pili
Porins A and B

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3
Q

How does Neisseria Meningitidis take up iron?

A

Host transferrin

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4
Q

N. Meningitidis pathogenisis

A
  • Attach to non ciliated columnar epithelia cells of nasopharynx via pili
  • Internalized into phagocytic vacuoles
  • Replication occurs and transcytosis to subepithelial spaces
  • Polysaccharide capsule is major virulence determinant - blocks phagocytic destruction
  • LOS induces vascular damage, inflammation, thrombosis
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5
Q

N. Meningitidis carriage

A

Asymptomatic and usually transient - highest for school-age children and young adults

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6
Q

When is N. Meningitidis most common?

A

During the dry, cold months of the year

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7
Q

Meningitis Belt

A

Major epidemics on an 8-12 year cycle in Sub Saharan Africa

Occurs during the dry season

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8
Q

Most N. Meningitidis epidemic are associated with which serogroup?

A

Serogroup A

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9
Q

N. Meningitidis
Acute bacterial meningitis:
Infants:
Older Children/Adults:

A

Acute bacterial meningitis: Abrupt onset of chills, fever, severe headache, meningeal inflammation
Infants: irritability, refusal to take food, seizures, disturbed motor tone, coma
Older Children/Adults: altered mental status, severe headache

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10
Q

Petechiae:
Purpura:

A

Petechiae: Minute hemorrhagic spots in the skin
Purpura: Hemorrhagic spots

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11
Q

N. Meningitidis - Laboratory Diagnosis

A
  • Gram stain of CSF
  • Blood culture
  • Oxidase positive, gram negative diplococci
  • Biochemical tests
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12
Q

N. Meningitidis treatment - vaccination

A
  • Serogroup tetravalent vaccine specific for A, C, Y and W135
  • Tetravalent vaccine - conjugate diptheria toxoid
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13
Q

N. Meningitidis drug treatment

A

Cefotaxime
Ceftriaxone
Penicillin G

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14
Q

Why is Group B meningitidis hard to treat?

A

K1 capsular polysaccharide in E. Coli is identical to group B antigen - hard to make selective vaccine

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15
Q

4CMenB

A

4 components of the serogroup B bacterium

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16
Q

Which Meningitis serogroup is most often associated with infections in infants and children?

A

Serogroup B

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17
Q

Neisseria gonorrhea - structure

A

Gram negative diplococci, oxidase positive
Does not posses a polysaccharide capsule
Possesses pili

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18
Q

N. Gonorrhea is a _____ specific pathogen and is sensitive to ____

A

human; cold

19
Q

N. Gonorrhea surface antigens: porins

A

Trimeric major outer membrane proteins that form pores for the passive uptake of nutrients
Expression of PorB - interferes with neutrophil degranulation, facilitates bacterial invasion and resistant to complement

20
Q

N. Gonorrhea surface antigens: Opa proteins

A
  • Opaque vs. Transparent
  • Opaque colonies (Gonococci expressing proteins) are usually localized infections - those from disseminated infections are usually transparent
  • Mediate binding to epithelial cells
21
Q

N. Gonorrhea surface antigens: Receptors for human transferrin

A

Mediate iron uptake in human hosts

22
Q

N. Gonorrhea surface antigens: LOS

A

Lipooligosaccharide - core oligosaccharide without the O antigens side chain

23
Q

Pathogenesis - Gonocci

A
  • Acquisition by sexual contact with an infected individual
  • Attachment to non ciliated epithelial cells; transcytosis to subepithelial spaces
  • Replication and release of LOS
  • Inflammatory response - damage to urethra or vagina
24
Q

For which Gonococcal structures do humans make antibodies?

A

Pillins, Opa proteins, LOS, and bacterial antigens that block the anti-pillin, Opa or LOS antibodies

25
Q

How are Gonoccal antigens highly variable?

A

Pili: phase variation (On or off) and antigenic variation (alter epitopes through recombination)
PorB - serological variation - many antigenic types

26
Q

Why is there no vaccine for Gonococci

A

No capsule, highly variable surface proteins

27
Q

Asymptomatic carriage of Gonorrhea is more common in ____

A

Women

28
Q

Women have a ____% risk of acquiring infection after single exposure; men have a ____% risk

A

50%; 20%

29
Q

Clinical presentation of Gonorrhea: Men

A

Purulent urethral discharge and dysuria 2-5 days post exposure (95% of infected men will be symptomatic)

30
Q

Clinical presentation of Gonorrhea: Women

A

Vaginal discharge, dysuria and abdominal pain - can become pelvic inflammatory disease

31
Q

Laboratory Diagnosis of Gonorrhea

A

Gram stain
Culture and biochemical identification
Nucleic acid amplification assays

32
Q

Treatment of Gonorrhea

A

1st line therapy: dual therapy with ceftriazone

2nd line therapy: cefixim and either azithromycin or doxycycline

33
Q

Chlamydia and Chlamydophila

A

Obligate intracellular parasites once considered viruses

34
Q

Chlamydia and Chlamydophila: structure

A

Typical gram-negative envelope with lipopolysaccharide

Do not synthesize peptidoglycan - no cell wall

35
Q

Chlamydia and Chlamydophila: Life cycle (2 forms)

A
  1. Elementary body - infectious form, stable in the environment because of highly cross-linked outer membrane structure
  2. Reticulate body - Replicative intracellular form, metabolically active, osmotically fragile, not stable to the environment - replicate by binary fission
36
Q

Inclusion body

A

Chlamydia replicate within the protective environment of the inclusion body

37
Q

Chlamydia Pathogenesis

A
  • C. Trachomatis EBs attach to nonciliated columnar cuboidal or transitional epithelial cells
  • Replicate within mononuclear phagocytes
  • Access through abrasions or lesions - primary lesion occurs at the site
  • Inguinal nodes become inflamed and swell
38
Q

What is the most common bacterial STD in the US?

A

C. trachomatis (1.3 million cases in 2010 in the US)

39
Q

Approximately ___% of women and ___% of men have asymptomatic C. Trachomatis infection

A

80%; 25%

40
Q

Reiter syndrome

A

Usually occurs in young Caucasian males - urethritis, conjunctivitis (C. Trachomatis)

41
Q

C. Trachomatis and Inclusion Conjunctivitis

A

Progressive disease that can lead to blindness

  • Eyelashes turn inward abrading the cornea
  • Loss of vision
  • Infections occur predominantly in children whose living conditions are crowded
42
Q

Chlamydia laboratory diagnosis

A
  • Cytology
  • Antigen detection
  • Nucleic acid amplification
  • Culture
43
Q

Common properties of N. Gonorrhoeae and C. Trachomatis

A
  • Gram negative
  • Results in inflammatory symptoms
  • Target non ciliated columnar epithelia cells
  • Can be asymptomatic
  • Should be treated promptly to prevent spread
  • No vaccine
  • Number 1 (Chlamydia) and Number 2 (N. Gonorrhoeae) bacterial STDs in the US

IAHI Block 2 (12 decks)

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