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SMP - MIM Part 2 > Lecture 7 - STDs > Flashcards

Lecture 7 - STDs Flashcards

1
Q

What are the 2 Neisseria pathogens?

A

N. gonorrhoeae (STD) and N. meningitidis

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2
Q

Describe Neisseria bacteria.

A

Gram-negative diplococci (cocci in pairs) that are oxidase-positive and only infect humans

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3
Q

Are there vaccines against Neisseria, Chlamydia, and syphilis bacteria?

A

NOPE (only against N. meningitidis)

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4
Q

How common is Neisseria gonorrhoeae?

A

2nd most common STD in the US

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5
Q

Where is the highest incidence of Neissesia gonorrhoeae globally?

A

Some parts of the US

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6
Q

What does dysuria mean?

A

Painful urination

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7
Q

Are symptoms of GC the same in males and females?

A

5 x more asymptomatic females than males

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8
Q

Symptoms of GC? What to note?

A

Reddened urethral meatus with a purulent discharge, without lesions or lymphadenopathy = gonococcal urethritis

NOTE: differential diagnosis should include chlamydia and gonorrhea: clinical presentation is consistent with gonorrhea,
although chlamydia cannot be ruled out

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9
Q

What 4 STDs can travel together?

A
  1. GC
  2. Chlamydia
  3. Syphilis
  4. HIV
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10
Q

Pathogenesis of GC?

A
  1. Attachment: 2- steps: distant with pili and firm with OPA
  2. Endocytosis by urethral or vaginal epithelia
  3. Transport to basal surface of epithelial cell
  4. Exocytosis to subepithelial tissue through the ECM
  5. Release to mucosal surface
  6. Host innate immune cells (MOs and neutrophils) phagocytose the pathogen but some survive within the MOs and get released
    7a. Host cell damage as LPS activates MO cytokine TNF causing apoptosis of host epithelial cells => bacteria get escape back into the lumen
    7b. Neutrophils with phagocytosed bacteria travel to the lumen => PMN-rich exudate
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11
Q

GC incubation period?

A

2-5 days

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12
Q

Where is the GC infection located in females?

A
  1. Urogenital cervix (80-90%)
  2. Rectum (40%)
  3. Pharynx (10-20%)
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13
Q

When do GC symptoms appear in females?

A

After 10 days of infection

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14
Q

Complication of GC infection in females? How often does this occur?

A

PID due to the GC spreading to reproductive organs causing irreversible damage to the uterus, ovaries, fallopian tubes, or other parts of the
female reproductive system

Happens in 10-20% of cases and is the primary preventable cause of infertility in women

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15
Q

What is unique about GC infection in females?

A

There is a blood-borne phase of the infection causing arthritis-dermatitis syndrome

Less often disseminated infection in males

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16
Q

Locations of GC infections in males?

A
  1. Urethritis
  2. Rectum
  3. Pharynx
  4. Epididymis
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17
Q

What happens if you biopsy the lesions caused by a disseminated gonoccocal disease?

A

Inflammatory response to the infection and by that time the infection would have already cleared so would not be able to make a diagnosis of what the lesions contained

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18
Q

What does it mean for a gram stain to be negative?

A

The organism is gram -

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19
Q

What media used to culture GC? What to note?

A

Chocolate agar (would be negative on blood agar plate)

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20
Q

Result of nucleic acid amplification test (NAAT) from rectal, oral, or urogenital swabs for GC? How does it work?

A

Positive for both GC and chlamydia if both present (PCR-based to test DNA)

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21
Q

Why is it hard to diagnose females with GC infection?

A

Because false positives in cultures and swabs very common since other gram - diplococci are normal flora

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22
Q

What are patients infection with N. gonorrhoeae often co-infected with?

A

C. trachomatis

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23
Q

How to screen for syphilis?

A

RPR or VDRL

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24
Q

What is an indication for HIV counseling?

A

History of risky sexual behavior

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25
Treatment for GC infection? What to note?
Ceftriaxone 125 mg intramuscular injection + doxycycline 100 mg orally twice a day for 7 days (only for the chlamydia as they often travel together) NOTE: resistance is common to most other antibacterial drugs
26
Treatment for chlamydia infection?
Doxycycline 100 mg orally twice a day for 7 days
27
How does GC infection appear in colony?
2 different appearances: either opaque or transparent based on the OPA protein
28
What is the gonococcal isolate surveillance project (GISP)?
4 regional labs do monthly tests for antibacterial resistance of gonoccocal infections sent from across the country and send this info to the CDC
29
What is the drug ceftriaxone?
3rd generation cephalosporin that is a cell wall inhibitor
30
What drugs were originally used to treat GC infections until the bacteria were completely resistant?
1. Penicillins 2. Quinolines 3. Cefixime 4. Ciprofloxacin
31
What to look out for once you have treated a GC infection? Explain. What does this explain?
Reinfection is very common because no immunity due to antigenic variation either during infection or a new infected partner Explains the fact that there is no vaccine for gonorrhea
32
What are the 2 mechanisms of antigenic variation of GC infections?
1. Pilin protein: recombination among silent minicassettes and expressed ones (separated by highly conserved DNA sequences, which allow the recombination)=> variant pilE gene with its own sequences of MCs 2. Opa surface protein: transcription stops, so protein not made, then is initiated at some point later again
33
What is the pilin protein of N. gonorrhoeae?
Major adhesin forming pili and composed of 6 minicassettes, which are each antigenically different
34
2 genes for the the pilin protein of N. gonorrhoeae?
1. pilS = silent (6 different MCs on 6 different pilS genes) | 2. pilE = expressed, because contains a promoter
35
What is post-gonococcal urethritis? Other name?
Co-infection with GC and chlamydia => GC symptoms appear first because it grows faster in the host than chlamydia = nongonococcal urethritis
36
Nongonococcal urethritis incubation period?
5-10 days
37
Describe Chlamydiae bacteria.
Obligate intracellular bacteria that are energy parasites (they cannot make their own ATP) and are like gram negative in structure, but their peptidoglycan is different
38
How to cultivate Chlamydiae bacteria?
Not cultivable in the lab on media => require living cells for growth
39
Describe the life cycle of Chlamydiae bacteria.
Life cycle (aka infectious cycle) comprised of two growth forms: 1. Elementary body (EB): smaller, infectious, rigid cell wall, and incapable of cell division 2. Reticulate body (RB): larger, fragile cell wall, capable of division but unable to survive extracellularly 1. EBs attach to epithelial cells and are phagocytosed 2. Once inside the host cell, the organism shuts down apoptotic pathways of the cell to prevent it from dying 3. Inside the epithelial cells, the EBs convert to the RB form 4. RBs divide within vacuoles of the epithelial cells 5. Eventually, all the RBs convert back to EBs 6. Organism turns back on host cell apoptosis so that the EBs can be released to infect more cells
40
What cells do Chlamydiae bacteria target?
Primarily epithelial cells: cervix and urethra
41
Leading cause of STD in the US?
Chalmydia trachomatis
42
Other than Chlamydiae trachomatis, what do other species/serotypes cause?
Pneumonia and ocular infections
43
Why is reinfection with Chlamydiae bacteria common? Why?
Because host immunity never develops => we do not know why
44
2 antibiotics against Chlamydiae bacteria?
1. Tetracyclines | 2. Erythromycin
45
Which are more resistant to bacteria: GC or Chlamydiae?
GC
46
What does infection with Treponema pallidum cause?
Syphilis with chancre
47
7 stages of syphilis if untreated?
1. Incubation period: 3 weeks 2. Primary syphilis: lasts for 2-6 weeks, with chancres, and during this time, the organism disseminates into the bloodstream, traveling to other tissues of the body 3. Asymptomatic phase: 2 weeks-6 months 4. Secondary syphilis: lasts 2-6 weeks with skin, mucous membranes, and LN lesions 5. Latent syphilis 6. Asymptomatic phase: 3-30 years 7. Tertiary syphilis: in association with a breakdown in host immunity and overreaction by some parts of the immune system, residual organisms begin replicating again, this lasts 2-6 weeks with gummas (nodules in skin and bones), CV and neurosyphilis
48
What species can Treponema pallidum infect?
Humans only
49
How to cultivate Treponema pallidum?
Cannot cultivate it in media
50
What kind of organism is Treponema pallidum?
Spirochete
51
What is a chancre?
Firm, painless, non-itchy skin ulceration
52
How has the incidence of syphilis changed?
Increased (more in males than females)
53
In what population is syphilis most common?
Men who have sex with men
54
How to diagnose syphilis?
1. Dark-field or fluorescence microscopy 2. Antibody tests 3. Silver staining
55
What to screen for when syphilis is suspected?
1. Syphilis 2. GC 3. HIV 4. Chlamydia
56
Treatment for syphilis?
Penicillin G, one dosage if case is less than 1 year; additional if > 1 year
57
Why is syphilis non-stainable?
Because it is small and very slender
58
Can Treponema pallidum survive away from humans?
NOPE - very sensitive to disinfectants, heat, and drying and humans are the only known host
59
Where is the tertiary stage of syphilis rare? Why?
Developed countries because of good detection methods, including serological assays
60
Why is syphilis sometimes called the "great imitator"?
Because its symptoms in secondary syphilis mimic many other diseases with involvement of skin, CV, respiratory system, lymphadenitis, and CNS
61
Can secondary syphilis patients transmit the disease?
YUP

SMP - MIM Part 2 (13 decks)

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