STIs Flashcards
Why does previous infection with N. gonorrhoeae not confer immunity?
Antigenic variation- especially of pili
What is antigenic variation? What is phase variation?
Antigenic variation- mechanism by which pathogen changes surface proteins to evade host immune system
Phase variation- switching on and off expression of proteins
How does N. gonorrhoeae prevent phagocytosis?
IgA protease- cleaves the Fc portion of human IgA, preventing opsonization
Both men and women can be asymptomatic carriers of N. gonorrhoeae. Is the prevalence of asymptomatic carriers greater in men or women?
Women- risk of PID
Gonococcal infection in children necessitates what actions?
Suspect child abuse
Contact police and social workers
What is the appearance of gram stains of urethral or endocervical exudates in a patient with N. gonorrhoeae infection?
Gram negative diplococci within PMNs
Is gram staining for a urogenital infection with N. gonorrhoeae more sensitive/specific in men or women?
Men
Patients infected with N. gonorrhoeae are often co-infected with what organism?
C. trachomatis
Because N. gonorrhoeae can produce insidious disease, treatment of known sexual contacts of a patient with this disease is necessary. What is the treatment?
IM dose of ceftriaxone
po dose of Azithromycin
What is the treatment of ocular infection with N. gonnorheae/C. trachomatis?
N. gonnorheae- ceftriaxone
C. trachomatis- erythromycin
Why are Chlamydiae obligate intracellular pathogens?
They cannot synthesizes ATP, thus, they depend on host cell for energy production
What stain can be used to visualize cells infected with Chlamydia?
Giemsa stain
Detail the biphasic life cycle of Chlamydiae.
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.
In what regions does lymphogranuloma venereum principally occur?
Africa
South America
Detail the clinical manifestations fo lymphogranuloma venerum.
Begins as small ulcer on genitalia, followed by lymphadenopathy of inguinal lymph nodes.
What testing method has become the recommended as the preferred method to detect GC and CT infections?
NAATs- nucleic acid amplification tests
What bacteria causes syphilis?
Treponema pallidum
What are the clinical features of stage 1 syphilis?
Painless chancre
How can you diagnose stage 1 syphilis?
Dark-field microscopy to visualize treponemes in fluid from chancre
What are the clinical features of stage 2 syphilis?
Disseminated disease with constitutional symptoms. Maculopapular rash (including palms and soles)
What are the clinical features of stage 3 syphilis?
Gummas
Aortitis
Neurosyphilis
VDRL detects nonspecific antibody that reacts with beef cardiolipin. The test is sensitive for syphilis, but what can cause false positives?
Viral infections
Drugs
Rheumatic fever
Lupus/leprosy
What is a Herxheimer reaction?
Flu like syndrome after antibiotics are started
What is the flu like syndrome that can occur in a patient with syphilis after they have been given antibiotics?
Herxheimer reaction
Leptospirosis interrogans is found in water contaminated with animal urine. What disease does this bacteria cause?
Leptospirosis- flu like symptom with myalgias, jaundice, photophobia, conjunctival suffusion
Weil disease- icterohemorrhagic leptospirosis (severe form with azotemia)
A patient with syphilis is allergic to penicillin, how can they be treated?
Azithromycin
What diseases are caused by C. trachomatis?
Reactive arthritis
Follicular conjunctivitis
Urethritis
PID
What disease are caused by C. pneumoniae and C. psittaci?
Atypical pneumoniae
What is the treatment for Chlaymydia infection?
Azithromycin
Why are beta-lactam antibiotics not very effective against Chlamydia?
Cell wall lacks peptidoglycan
Chlamydia trachomatis serotypes ABC cause what disease?
Chronic infection leads to blindness
What C. trachomatis serotypes cause Lymphogranuloma venereum?
L1,2,3
How do you treat lymphogranuloma venereum?
Doxycycline
