STIs

Question 1

Why does previous infection with N. gonorrhoeae not confer immunity?

Answer 1

Antigenic variation- especially of pili

Question 2

What is antigenic variation? What is phase variation?

Answer 2

Antigenic variation- mechanism by which pathogen changes surface proteins to evade host immune system
Phase variation- switching on and off expression of proteins

Question 3

How does N. gonorrhoeae prevent phagocytosis?

Answer 3

IgA protease- cleaves the Fc portion of human IgA, preventing opsonization

Question 4

Both men and women can be asymptomatic carriers of N. gonorrhoeae. Is the prevalence of asymptomatic carriers greater in men or women?

Answer 4

Women- risk of PID

Question 5

Gonococcal infection in children necessitates what actions?

Answer 5

Suspect child abuse

Contact police and social workers

Question 6

What is the appearance of gram stains of urethral or endocervical exudates in a patient with N. gonorrhoeae infection?

Answer 6

Gram negative diplococci within PMNs

Question 7

Is gram staining for a urogenital infection with N. gonorrhoeae more sensitive/specific in men or women?

Answer 7

Men

Question 8

Patients infected with N. gonorrhoeae are often co-infected with what organism?

Answer 8

C. trachomatis

Question 9

Because N. gonorrhoeae can produce insidious disease, treatment of known sexual contacts of a patient with this disease is necessary. What is the treatment?

Answer 9

IM dose of ceftriaxone

po dose of Azithromycin

Question 10

What is the treatment of ocular infection with N. gonnorheae/C. trachomatis?

Answer 10

N. gonnorheae- ceftriaxone

C. trachomatis- erythromycin

Question 11

Why are Chlamydiae obligate intracellular pathogens?

Answer 11

They cannot synthesizes ATP, thus, they depend on host cell for energy production

Question 12

What stain can be used to visualize cells infected with Chlamydia?

Answer 12

Giemsa stain

Question 13

Detail the biphasic life cycle of Chlamydiae.

Answer 13

EB are infectious form.
RB are replicating form.
EB form infects cells and prevent phagosome-lysosome fusion. EBs reorganize to form RBs which replicate. RBs reorganize to form EBs. Host cell rupture releases EBs.

Question 14

In what regions does lymphogranuloma venereum principally occur?

Answer 14

Africa

South America

Question 15

Detail the clinical manifestations fo lymphogranuloma venerum.

Answer 15

Begins as small ulcer on genitalia, followed by lymphadenopathy of inguinal lymph nodes.

Question 16

What testing method has become the recommended as the preferred method to detect GC and CT infections?

Answer 16

NAATs- nucleic acid amplification tests

Question 17

What bacteria causes syphilis?

Answer 17

Treponema pallidum

Question 18

What are the clinical features of stage 1 syphilis?

Answer 18

Painless chancre

Question 19

How can you diagnose stage 1 syphilis?

Answer 19

Dark-field microscopy to visualize treponemes in fluid from chancre

Question 20

What are the clinical features of stage 2 syphilis?

Answer 20

Disseminated disease with constitutional symptoms. 
Maculopapular rash (including palms and soles)

Question 21

What are the clinical features of stage 3 syphilis?

Answer 21

Gummas
Aortitis
Neurosyphilis

Question 22

VDRL detects nonspecific antibody that reacts with beef cardiolipin. The test is sensitive for syphilis, but what can cause false positives?

Answer 22

Viral infections
Drugs
Rheumatic fever
Lupus/leprosy

Question 23

What is a Herxheimer reaction?

Answer 23

Flu like syndrome after antibiotics are started

Question 24

What is the flu like syndrome that can occur in a patient with syphilis after they have been given antibiotics?

Answer 24

Herxheimer reaction

Question 25

Leptospirosis interrogans is found in water contaminated with animal urine. What disease does this bacteria cause?

Answer 25

Leptospirosis- flu like symptom with myalgias, jaundice, photophobia, conjunctival suffusion Weil disease- icterohemorrhagic leptospirosis (severe form with azotemia)

Question 26

A patient with syphilis is allergic to penicillin, how can they be treated?

Answer 26

Azithromycin

Question 27

What diseases are caused by C. trachomatis?

Answer 27

Reactive arthritis Follicular conjunctivitis Urethritis PID

Question 28

What disease are caused by C. pneumoniae and C. psittaci?

Answer 28

Atypical pneumoniae

Question 29

What is the treatment for Chlaymydia infection?

Answer 29

Azithromycin

Question 30

Why are beta-lactam antibiotics not very effective against Chlamydia?

Answer 30

Cell wall lacks peptidoglycan

Question 31

Chlamydia trachomatis serotypes ABC cause what disease?

Answer 31

Chronic infection leads to blindness

Question 32

What C. trachomatis serotypes cause Lymphogranuloma venereum?

Answer 32

L1,2,3

Question 33

How do you treat lymphogranuloma venereum?

Answer 33

Doxycycline