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Clinical Microbiology > STIs > Flashcards

STIs Flashcards

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Biology 101 flashcards
1
Q

Neisseria

A 
Aerobic gram negative cocci
Oxidase and catalase +
N. meningitidis = meningitis
N. gonorrhoeae = gonorrhea
All look the same under the microscope
We are all colonized by some non-pathogenic species
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2
Q

N. gonorrhoeae
(gram stain, shape, oxidase, catalase, intra/extracellular, media it grows on, transmission, what epithelia does it infect)

A

Aerobic gram negative diplococci
Oxidase and catalase +
Often appears intracellular on gram stain
Very fastidious (will not grow on SBA, may not survive drying and dies rapidly during transport)
Grow on Thayer Martin media
Transmission from male to female more likely
Primarily infects columnar or cuboidal epithelium

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3
Q

Superoxol Test

A

Performed with 30% H2o2

Really bubbly

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4
Q

One way to tell between gonorrhea and chlamydia

A

GC: copius discharge
C: no discharge

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5
Q

2 major virulence factors for N. gonorrhoeae

A
  1. Pili (adherence to mucosal surfaces, inhibit killing by neutrophils)
  2. Outer membrane (facilitate invasion, has endotoxin)
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6
Q

Sensitivity

A

The proportion of actual POSITIVES that are correctly identified as positive

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7
Q

Specificity

A

The proportion of NEGATIVES that are correctly identified

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8
Q

Positive predictive value

A

Proportion of patients with positive test results who are correctly diagnosed
Depends on the prevalence of the disease

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9
Q

Negative predictive value

A

Proportion of patients with negative test results who are correctly diagnosed

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10
Q

Gonorrhoea culture/diagnosis

A

Grows on chocolate agars with antibiotics (nutritous medial
Take urethral swabs from male and cervical swabs from females
Does NOT grow on SBA

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11
Q

GC culture vs PCR samples for males and females

A

Culture: males use urethral swabs, females need cervical swabs
PCR: males need 1st voided urine, females need vaginal swabs

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12
Q

What do we use to treat GC?

A

800mg Cefixime or 250mg ceftriaxone intramuscularly

Both are cephalosporins

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13
Q

3 primary Chlamydia pathogens

A

C. psittaci (resp tract infections from birds)
C. pneumoniae
C. trachomatic

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14
Q

Chlamydia life cycle

A 
Biphasic
Elementary bodies (infective form) attaches to host cell, endocytosed, morphs into reticulate body (undergoes multiplication by binary fission), then differentiates back to elementary body, released from cell, on to infect others
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15
Q

Chlamydia causes __ in men vs women

A

Men: urethritis
Women: cervicitis and PID

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16
Q

Lab Diagnosis for Chlamydia (4)

A

Antigen detection
Immuno-fluorescence
Cell culture
PCR

17
Q

Chlamydia treatment (1st and 2nd line)

A

1st line: 1 gram Azithromycin (4 pills, single dose)

2nd line: 100 mg BID doxycycline (2 doses a day for 10 days)

18
Q

Haemophilus ducreyi

A

Produces Chancroid lesions
Tender, non indurated irregular ulcers
Infection is localized, but frequently spreads to regional lymph nodes
Lymph nodes enlarged and painful
Intra or extracellular bacteria, appear as cocco-bacilli or short rods
Gram varibale
Arranged in parallel chains (school of risk or rail road track appearance)
2 hotspots: Nairobi and Winnipeg
Fastidious - grows slowly on chocolate but using 2 media is optimal

19
Q

Media for H. ducreyi

A

Gonococcal agar based or a Mueller Hinton based medium can be used, and add:
1% IsoVitalex, 5% chocolatized horse blood or 1% hemoglobin, 5% fetal calf serum, Vanco

20
Q

Molluscum contagiousum

A

Large enveloped DNA, poxvirus family
Only found in humans (no animal reservoir)
Diagnosis: EM, clincal appearance, PCR
Not painful but can be itchy (can lead to secondary infections and scarring)
Affects any area of the body
High incidence in children, immunocompromised, sexually active adults
Transmitted through direct contact and fomites
Long incubation period and lasts a long time, but will go away on its own (does not stay in body)
Treat with chemical or surgical removal of lesions

21
Q

Clinical appearance of Molluscum contagiousum

A

Flesh coloured lesions
Dome-shaped with dimpled center
Diameter 1-5 mm

22
Q

Herpes simplex virus

A

Enveloped, icosahedral capid, dsDNA
Thymidine kinase and DNA polymerase (acyclovir)
Spectrum of disease: asymptomatic, lesions, encephalitis, recurrent meningitis, ocular infections

23
Q

HSV 1 versus HSV 2

A

1: frequently associated with oral/ocular infections (rising in cases of genital herpes though) - less reoccurrences, less asymptomatic shedding
2: most frequently associated with genital infections

24
Q

Molleret’s

A

Meningitis from herpes
Recurrent
Will go away on its own without treatment

25
Q

Latency and Reactivation of herpes

A
  1. Local replication and entry of virus into cutaneous neurons
  2. Centipetal migration in the axon
  3. Reactivation and replication
  4. Centrifugal migration to the epidermis
26
Q

Melt curve analysis

A

Way to diagnose herpes
Real time PCR
Uses the primers for both 1 and 2 and based on what temperature they probes melt off you can generate a melting temperature which is characteristic for one of them

27
Q

Acyclovir

A

Nucleoside analog - chain terminator
Blocks viral DNA polymerase
Has to be phosphorylated to be activated
First activation with HSV thymidine kinase, next 2 with host enzymes

28
Q

Human Papilloma Virus

A

Papillomaviridae
Non-enveloped, dsDNA virus
Most prevalent STD
Cannot be grown in culture - molecular detection possible and use Pap test
Oncogenic virus
Contact transmission
Acquisition shortly after onset of sexual activity

29
Q

Respiratory papillomatosis

A

Benign warts in the upper airway (may cause obstruction, can surgically remove)
Caused by HPV 6 and 11

30
Q

Treating genital warts

A

Usually for aesthetic reasons
Podophyllin resin, trichloroacitic acid, cryotherapy
Burn or freeze them off

31
Q

Why are only some HPV strains oncogenic?

A

High risk HPV has a circular gene
Gets integrated into the genome and splits a gene that regulates expression of E6 and E7
These have effects on the cell that will lead to its proliferation

32
Q

E6 vs E7

A

E6: binds and leads to degradation of p53 (low risk types do NOT bind p53)
E7: binds the retinoblastoma TSG product so the transcription factor is free to activate the cell cycle (low risk types bind poorly to this)

33
Q

Gardasil vs Cervarix

A

G: Types 16, 18, 6, 11
C: Types 16, 18 only

34
Q

HPV L1 Virus-Like-Particle Vaccine

A 
Give a pseudovirus from the capsid proteins
Very safe (no replication)

Clinical Microbiology (25 decks)

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