Sexually Transmitted Infections Flashcards
What are the three bacterial species which produce STDs?
1) neisseria
2) chlamydia
3) treponema
What are the morphological characteristics of Neisseria gonorrhoeae?
1) gram-negative
2) diplococci
3) oxidase positive
Why are there no reliable animal models of gonorrhea?
because it only infects humans
Which STDs have the highest incidence in the US?
1) chlamydia
2) gonorrhea
What are the initial symptoms of a GC infection?
1) urethral or cervical discharge
2) dysuria
3) urethritis
What does flank pain indicate on physical exam?
kidney infection or urinary tract involvement
What is the differential diagnosis for gonorrhea?
Chlamydia, and then HIV and syphilis
Why do you consider HIV and syphilis with GC infection?
Because STDs travel together!
What two proteins cause gonorrhea to attach to the uretrhal or vaginal epithelium?
1) pilus protein
2) OPA protein
How does gonorrhea infect a host?
endocytosis and transport into epithelial cells. exocytosis and collection by immune system. Host cell damage and then release to mucosal surface for reinfection.
What is one of the signs of a gonorrhea infection?
PMN-rich exudate
Where can a GC infection go especially in females?
Dissemination through the blood causing disseminated disease`
What activates TNF in a GC infection?
LPS
What is disseminated gonococcal disease characterized by?
skin lesions, traveling arthritis
Where are 80-90% of GC cases found in women?
urogenital cervix
What is a major side effect of GC infection in women?
PID
What percentage of GC infections in women become PID?
10-20%
What are two distinguishing characteristics of GC infection in women vs. men?
- 5x higher rate of being asymptomatic
- infection lasts longer - ~10 days
What is the number one preventable cause of infertility in women?
PID
How is GC diagnosed?
By taking a swab of the discharge
How does GC grow on blood agar? on chocolate agar?
GC doesn’t grow on blood agar, but will grow on chocolate agar
Why are false positives of GC a common occurrence in females?
Gram-negative diplococci are a common part of the normal vaginal microflora
What are NAATs?
Nucleic Acid Amplification Tests
What is the standard treatment for GC? Why?
Ceftriaxone 250mg and doxycycline. Ceftriaxone 250mg for growing resistance and doxycycline for NGU
What is doxycycline used in treatment of GC infection?
Because Chlamydia symptoms show up later than GC and as co-occurring infections are common it is better to treat both
What is NGU?
Non-gonococcal urethritis
Which countries/regions have the highest rate of GC infection?
Former Soviet bloc countries, and parts of the MWern US
Why is reinfection with GC common?
There is no immunity to GC. Antigenic variation occurs during infection
What is the major adhesion protein in GC?
Pilin
Why is pilin antigenically variable?
There are many gene cassettes of the pilin gene which can be tandemly arranged and recombined
What are some unique properties of chlamydia bacteria?
- obligate unicellular bacteria
- “energy parasite” using host’s machinery to make ATP as it cannot on its own
- cannot be cultured as it needs to have living cells to grow
- similar to gram-negative bacteria
What two forms does chlamydia come in?
1) elementary body
2) reticulate body
Which life form of chlamydia is infectious?
elementary body
Which life form is larger?
reticulate body
Which life form is intracellular?
reticulate body
Where is chlamydia primarily pathogenic?
cervical and urethral epithelium
What are the two antibiotics which Chlamydia is primarily susceptible to?
- tetracyclines
- erythromycin
What is the bacteria which causes syphilis?
treponema pallidum
What type of shape is treponema?
spiral-shaped rod
Can syphilis be cultured?
no!
What is the characteristic lesion in primary syphilis?
chancre
What is a chancre?
firm, painless, non-itchy skin ulceration
What is the reservoir for syphilis?
Humans only
What population has a higher incidence of STDs in general?
HIV+ individuals
If syphilis is untreated, what happens?
You get a larger rash with palmar and solar lesions which indicates secondary syphilis
How long can syphilis stay latent?
3-30 years
Which population has an increase in the incidence in syphilis in the past 15 years?
males who have sex with other males
How do you work-up syphilis?
- dark-field or fluorescent microscopy
- antibody tests
- GC, chlamydia, and HIV screens if negative
What is the primary treatment of choice for syphilis and why?
Pencillin because there is little if any abx resistance
Is the treponema bacteria particularly hardy?
No, it cannot survive away from humans, nor in heat, other conditions.
Why is syphilis sometimes called the “great imitator”?
Because its primary symptoms mimic those of other diseases
