14. Sexually Transmitted Infections Flashcards
3 nationally reportable STIs and their common traits
chlamydia （衣原体）, gonorrhea (淋病） & syphilis (梅毒)
- Treatable by antibiotics
- Many go undiagnosed leaving individual at risk of numerous adverse consequences
- Limited resources make it challenging to identify and treat STIs
Chlamydia: agent, U.S. epi
agent: Chlamydia trachomatis, an obligate intracellular bacterial agent
Most common notifiable disease in the U.S.
Most prevalent STI in the U.S.
1995 - Became nationally notifiable • 2000 – All 50 states and D.C. required reporting • 2000-2011 – expanded use of more sensitive diagnostic tests
Chlamydia in Females (symptoms, complications)
Most commonly infects the cervix
Up to 90% of cases are asymptomatic
Symptomatic cases: vaginal discharge, abdominal pain, pain/burning with urination
If untreated, 30% of women will develop pelvic inflammatory disease (PID)
Pregnancy complications: preterm delivery, transmission to baby during birth process (20-50%)
Chlamydia in Male (symptoms, complications)
Causes urethritis (inflammation of the urethra) 尿道感染
Up to 70% of cases are asymptomatic
Symptomatic cases: penile discharge, testicular (睾丸) pain, pain/burning with urination
Can cause rectal (直肠) infection in MSM
Increasing chlamydia rates may reflect
Increase in incidence
Increase in screening coverage
Use of more sensitive diagnostic tests
More complete reporting
Gonorrhea: agent, U.S. epi
Caused by Neisseria gonorrhoeae, a gram-negative diplococcus bacterial agent 双球菌
2nd most commonly reported notifiable disease in the United States
CDC approximates > 800,000 new infections annually
Gonorrhea in Females (symptoms, complications)
Most commonly infects the cervix
Up to 70% of cases are asymptomatic
Symptomatic cases: vaginal itching, vaginal discharge, occasionally intermenstrual bleeding
If untreated, 10-20% of women will develop pelvic inflammatory disease (PID)
Pregnancy complications: infection of amniotic fluid, preterm birth, low birth weight, spontaneous abortions, transmission to baby during birth process (30-50%)
Gonorrhea in Male (symptoms, complications)
Causes urethritis (inflammation of the urethra)
Clinic-based studies suggest that most are symptomatic
Common symptoms: penile discharge & pain with urination
Can cause rectal infection in MSM
Pelvic Inflammatory Disease (symptoms, complications)
Infection of the female reproductive organs: uterus, fallopian tubes, ovaries
Typically occurs when STI bacteria spread from the cervix
May be asymptomatic, or cause mild or severe symptoms
Many potential complications if left untreated
- Scar tissue
- Ectopic pregnancy (tubal pregnancy)
- Infertility
- Chronic pelvic pain
- Tubo-ovarian abscess 附件肿块
Neonatal Conjunctivitis (symptoms, agent, prevention)
symptoms:
- inflammation of the conjunctiva (thin clear tissue that lines the eye & eyelid)
- Infection may spread to other areas of the body. If untreated, can lead to blindness
- Occurs during the first 4 weeks of life
- Infants acquire infection while passing through the birth canal
Agent: Chlamydia is most common infectious agent
Prevention: State law requires most hospitals to administer antibiotic drops or ointment to help prevent neonatal conjunctivitis due to STIs
Testing for Chlamydia and Gonorrhea
Most widely used is the Nucleic Acid Amplification Test (NAAT)
- recommended for both screening and diagnostic testing
- Variety of specimens can be used
- Female – Vaginal & cervical swabs, urine
- Male – Urethral swabs, urine
- Very high sensitivity (well above 90%) and specificity (usually ≥99%)
- At home test kits have become available
Treatment for Chlamydia and Gonorrhea (goal)
Goals of Treatment
- Decrease transmission to others (sexual partners, infants)
- Prevent complications of infections
Treatment & Follow-up
- Antibiotics
- Chlamydia: One-time antibiotic tx by mouth (azithromycin)
- Gonorrhea: One-time antibiotic tx by IM injection (ceftriaxone) PLUS one-time antibiotic tx by mouth (azithromycin)
Treatment of sexual partner(s)
Avoid sexual activity for 7 days after treatment for self & partner (to avoid reinfection!)
Retesting: 3 months after treatment to evaluate possible reinfection
Recommend HIV testing
Syphilis: agent, U.S. epi
STI caused by spiral shaped bacteria Treponema pallidum
Associated with significant complications if left untreated
Can facilitate the transmission & acquisition of HIV
Untreated syphilis in pregnant woman can lead to infection in fetus in up to 80% of cases
Reporting of syphilis began in 1941
2000-2001: Lowest rate of reported cases since 1941
Rates have increased almost every year since then
Attributed to increase in cases in MSM
Syphilis: stage, symptoms
- Primary Syphilis
- 3 weeks after initial exposure
- Develop chancre (painless ulcer), highly infectious
- Heals in 2-3 weeks if left untreated
- Secondary Syphilis
- 2 – 8 weeks after chancre appears
- Whole body rash, including palms & soles
- Condylomata lata on genitals (highly infectious)
- Resolves in 2-10 weeks if untreated
- Tertiary Syphilis
- Rare, can be fatal, develops in a subset of untreated patients
- Can appear 10-30 years after initial infection
- Affect multiple organ systems: brain, nerves, heart, eyes, vessels, liver, bones, joints
- Symptoms based on organ system affected
Testing for Syphilis
Definitive test: Darkfield microscopy
Alternative tests: immunoassays
