Sexually Transmitted Infections Flashcards
What is the leading reported infectious disease in the U.S., and who has the highest prevalence?
Chlamydia trachomatis, highest among sexually active teenagers
What are the infectious and metabolically active forms of Chlamydia?
Infectious - elementary body
Non-infectious - Reticulate body
Which body has stainable inclusion bodies and why?
Reticulate body, because it synthesized large amounts of glycogen which can be stained via iodine
What two diseases is Chlamydia a major risk factor for in women and why?
- Reactive arthritis - often implicated
2. Pelvic inflammatory disease - develops in 20-40% of women, leads to ectopic pregnancy / infertility
What are typical symptoms of Chlamydia infection in women?
You can have cervicitis, salpingitis, or urethral syndrome, but it is asymptomatic in >50% of cases
What does Chlamydia cause in men?
Urethritis (urethral discharge easier to detect in men)
Epididymitis
Orchitis
Also: Reactive arthritis
What infection does Chlamydia cause in neonates?
Inclusion conjunctivitis or pneumonia
Why does Chlamydia cause PID?
Tissue fibrosis occurs as a result of chronic or recurring infection with strong inflammatory immune responses but no immunity to re-infection
What is Lymphogranuloma venereum? What Chlamydia serotypes cause this?
L1, L2, and L3 (for lympho).
Small, painless ulcers on genitals, leads to swollen, painful inguinal lymph nodes that ulcerate and cause buboes.
Common in MSM
What Chlamydia serotypes cause follicular conjuncitivitis?
Occurs chronically in africa.
Serotypes A, B, C
A = Africa
B = Blindness
C = Chronic
What Chlamydia serotypes cause urethritis / PID?
D - K = Everything else.
How is Chlamydia diagnosed?
Collection of infected epithelial cells from infection site, then PCR from vaginal swab or urine specimen (men)
Why are Chlamydia and Neisseria gonorrhoeae infections common co-infections?
Gonococcal infections facilitate transmission of Chlamydia
What are the general characteristics of gonococcus? What cells do they grow in
Gram negative diplococci with fastidious growth requirements, thus they are facultatively intracellular in PMNs (neutrophils) or epithelial cells
What is a Thayer-Martin plate and why are they used to isolate gonococcus?
Chocolate agar plate (fastidious growth requirements, like H. influenze) + antibiotics which reduce other GU flora which could grow with it
What is the primary adhesion virulence factor of N. gonorrhoeae and how does it attach and evade host immune response?
Pili - binds human CD46 membrane receptor
- RNA level = Slipped strand mispairing - Change the pilus length and create pilus plus and pilus minus (do not survive) phenotypes
- DNA level = Antigenic variation, PilE = expression, must recombine with pilS (several loci) to express different amino acid sequence in pilus protein
What causes a major inflammatory response in gonorrhea?
Lipo-oligosaccharide (LOS), the equivalent to LPS but the gonorrhea variant. Can be sialyated to confer serum resistance and block neutrophil attachment
This causes major of damage in disease
What does gonorrhea in men look like?
Urethra is primary site of infection, dysuria and purulent urethral discharge (as opposed to mucoid discharge of chlamydia)
What does gonorrhea look like in women?
Often asymptomatic, endocervix is primary infection site, can cause vaginal discharge, pelvic pain, and urgency / frequency
Often asymptomatic and cause infertility due to salpingitis
What is disseminated gonococcal infection (DGI) and what does it cause?
Rare, causes an arthritis-dermatitis syndrome, with hemorrhagic lesions around feet and monoarticular arthritis
How can gonorrhea be detected in men vs women in the lab?
Symptomatic men = gram stains. Does not work for symptomatic women (need PCR).
Typically, just culture urethral discharge (men) or cervical swabs (women) on Thayer-Martin
Diplococci within PMN = diagnostic for men
Are gonorrhea oxidase positive?
Yes, oxidase positive
What is the morphology / characteristics of Treponema pallidum? How can it be seen?
Gram negative spirochete, obligate human pathogen which is very environmentally sensitive
Can be seen via darkfield microscopy
Can you get syphillis transplacentally?
Yes - fetus is susceptible any time during gestation
How does syphillis disseminate before a primary lesion occurs?
Disease of blood vessels and perivascular lymphatics. Pathogen invades mucous membranes and travels to perivascular lymphatics and lymph nodes / systemic circulation, before developing a primary lesion
What is primary syphillis? Where do they appear? When do they heal?
A “painless!!” chancre 3-4 weeks post contact, which is round, hard, with defined edges.
Appear on external genitalia, anal area, or lips. Females may have them on cervix so they cannot be seen. Visualize fluids of darkfield microscopy
Will heal spontaneously in 4-6 weeks
When does secondary syphilis develop and what are the symptoms? This is when the patient comes in for treatment typically
Develops 2-10 weeks following healing of primary lesion
Symptoms: fever, sore throat, rash, skin lesions on palms and soles is very diagnostic
It can be cleared by immune system or go latent
S(econdary) = Systemic
What is latent syphilis?
No signs and symptoms of syphilis, but patient is seroreactive. Antibiotic therapy will prevent progression to tertiary syphilis.
~40% of untreated patients will get tertiary, in 5 years at the earliest (15-20 is most common)
What is tertiary syphilis marked by?
Gummas - Granulomatous lesions of skin, bone, and joints due to host immune response.
Neurosyphilis - Argyll-Robertson pupils (constricts on accommodation but does not react to light), tabes dorsalis, dementia, optic atrophy, seizures
Cardiovascular syphilis - Aortic aneurysm
Is the organism often found in secondary and tertiary syphilis lesions?
Secondary - foot and palm rash = yes, very infectious
Tertiary - gummas - no, just host immune response typically
What typically happens to babies afflicted with congenital syphilis with respect to delivery time?
They are typically premature, with low birth weight.
May exhibit rhinitis, pneumonia, and failure to thrive 3-8 weeks post birth
For severe cases of congenital syphilis, what are some of the pathopneumonic exam findings?
- Hutchinson’s teeth - notched teeth
- Saddle nose - bend in nose
- Hard palate defect
- Short maxilla
- Protruding mandible
- Rhagades - linear scars on edge of mouth
- CN8 deafness
How does the VDRL / RPR test work?
It uses a cardiolipin to detect anti-cardiolipin antibodies in the patient’s serum, which can indicate the patient has syphilis. VDRL is quantitative and should fall after resolution of infection.
Works because:
Syphilis infection produces nonspecific antibodies that react with cardiolipin, a normally mitochondrial lipid which is produced in bacteria.
What are some sources of false positives for the VDRL test?
Other things which produce antibodies which react with cardiolipin. I.e:
V: Viral infection
D: Drugs
R: Rheumatic fever / heart disease
L: Lupus / Leprosy
Very sensitive for syphilis, but not specific
What is the Treponema-specific serologic diagnostic test?
Direct detection of antibody to T. palladium, as in fluorescence treponemal antibody absorption test - FTA-ABS
Specific but not sensitive. Also not affected by treatment (will not fall)
What is one really good test for seeing if T. pallidium is there?
Tp-PCR - treponema PCR
What is one STI commonly confused with syphilis and how can it be told apart?
Haemophilus ducreyi, an STI of developing countries
Produces a chancroid: soft-edged, and very painful
vs syphilis = chancre: hard, raised edge. not painful.
What is the most common curable STD?
Trichomonas vaginalis, with only 30% having symptoms
What is the morphology of Trichomonas? Where does it grow?
Flagellated protozoa. Highly motile with no cyst form, can survive on moist surfaces for 1-2 hours.
Inhabits vagina in women and urethra / prostate in men
Is it possible to get Trich non-sexually, and what does it eat?
Yes, but it’s rare
It eats lactobacillus normal flora
What is the major exam finding with Trich?
Strawberry cervix - colpitis macularis. Inflamed cervix and vagina, with punctate hemorrhagic spots
Are men or women more likely to be symptomatic in Trich?
Men are generally asymptomatic
Half of women exhibit symptoms in 5-28 days, with vaginal itching / burning, foamy / bad-smelling yellow-green discharge.
What is vaginitis vs vaginosis?
Vaginitis - inflammation of vagina caused by infection
Vaginosis - bacterial overgrowth due to altered balance of bacteria in the vagina, not considered an STI
What is the major cause of bacterial vaginosis?
Gardnerella vaginalis - a gram-variable coccobacillus. Often grows anaerobically in normal flora, but disruption can lead to a similar discharge as trich (frothy gray or yellow-green)
What is the most common fungal vaginosis? What can cause it?
Candida albicans - compromised cell-mediated immunity + pregnancy, diabetes, oral contraceptives use, and antibiotics
What is the consistency of fungal vaginosis in a yeast infection?
“cottage-cheese”, with accompanying burning / itching of genitals
who always do me a heppi
da memo
