Sexually Transmitted Infections Flashcards
What are sexually transmitted infections?
STI’s are infections transmitted primarily during sexual contact; commonly by any of the following routes of transmission:
- Oral-genital contact
- Vaginal intercourse
- Anal intercourse
- Anilingus
What are the common patterns of STI infections?
Vaginal / Urethral Discharge
Genital Lesions
Warts
**Pelvic Involvement Disorders (PID) **
Dermatological Conditions
Chacterise the microbe Neisseria gonorrhoeae
Neisseria gonorrhoeae is a **gram negative diplococci **
It adheres to columnar epithelial cells ( of which there are more of in younger women - may contribute to increased prevalence )
Have a **short incubation period of 2-7 **
Asymptomatic infection common in females (80%) but not males (urethritis) **(10%) **
There is increasing antibiotic resistance in Neisseria gonorrhoeae - largely due to the exchanging of genes beween respiratory microflora Neisseria with pathogenic STI Neisseria
What are the pathological consequences of a gonorrhoea infection?
If untreated, gonorrhoea can progress to result in:
Dissemination (0.5-3% of cases)
- **Arthritis **
- Disseminated maculopapular rashes
- Meningitis
- Endocarditis
-
Peri-hepatitis / Violin-string adhesions / Fitz Hugh Curtis Syndrome
- Organism capable of entering the abdominal cavity after ascending the fallopian tubes and creating adhesions of the liver ( a consequence of PID )
- Epididymitis
Pelvic Inflammatory Disease
- Tubal scarring
- Infertility (10-20%)
What is neonatal gonococcal opthalmia?
Neonatal gonococcal opthalmia is a gross purulent conjuctivitis
Is a aquired in the process of birth ( to a gonorrhoea infected mother) before becoming symptomatic in day 2-5 of life
Mild neonatal gonococcal opthalmia is indistinguishable from other causes of conjunctivitis
Treatment involves:
- IV cefotaxime (50mg/kg)
* No need for topical antibiotic treatment unlike other more common conjunctivitis - Irrigate eyes regularly
- Treat mother and sexual contacts
What diagnostic testing is involved in gonnorhoea diagnosis?
Diagnostic Specimens:
- Cervical Swab / Urethral Swabs
- Urine Sample
- Other as relevant: conjunctiva, pharynx, skin lesions, anal swab, blood specimens, synovial fluid
Culture media:
- Selective: Thayer-Martin Agar (colistin, vancomycin and nystatin)
- Non-selective : Chocolate blood agar in CO2
Nucleic acid amplification tests (NAAT)
- Combined Chlamydia and Neisseria detection from wither genital or first void urine samples
- Chlamydia co-infections ~50% of cases
How do you treat and prevent Gonnorrhoea?
Ceftriaxone (500mg) IM/IV + Azithromycin 1g oral (in case of chlamydia co-infection)
To prevent it:
- Barrier contraception
- Contact tracing
- Vaccine (in development)
Characterise the microbe **Chlamydia trachomatis **
**Chlamydia trachomatis **is an obligate intracellular parasite
The parasite *adheres to an invades columnar epithelium *
Different serotypes of the microbe cause different diseases:
D-K = genital infection ; L1-L3 = Lymphogranuloma Venereum (LGV) ; A-C = Trachoma
Discuss the life cycle of **chlamydia **
There are two forms of the chlamydia microbe:
Elementary Bodies: infectious, non-replicating and hardy
Reticulate Bodies: metabolically active and replicating
The life cycle consists of:
- Infectious elementary body attachment and entry to target columnar epithelial cell
- Formation of reticulate body
- Binary fission of reticulate body to replicate
- Reorganisation of reticulate bodies into elementary bodies
- Vast quantities of elementary bodies in cytoplasmic inclusion of host cell
- Rupture of host cell and release of infectious elementary body
Discuss the epidemiology and clinical signs of Chlamydia
Chlamydia is the most common STI
Causes cervicitis in females (although often asymptomatic) and urethritis in males
Male signs:
- Dysuria
- Meatal erythema
- Clear urethral discharge
- Testicular pain
- Prostatitis
Female signs:
- _Cervicitis / endometritis _
- Vaginal discharge
- Urethritis / Dysuria
- Irregular bleeding
- Pelvic pain and dysparenuia (painful intercourse)
- Pelvic inflammatory disease (acute + chronic)
What is lymphogranuloma venereum (LGV)?
** Lymphogranuloma venereum **is an **invasive lymphatic infection **caused by chlamydia
It generally results from chlamydia infecting or causing an ulcerative genital lesion before travelling via the lymphatics to cause suppurative inguinal lymphadenopathy
It is endemic in Africa, India, SE Asia and South America
Discuss Neonatal Chlamydia
Neonates can become infected with chlamydia by their positive mothers during passage through the birth canal.
50% of births to Chlamydia positive mothers result in neonatal Chlamydia
Presents as conjunctivitis (25%) or pneumonia (10%)
Must treat the child and the parents
What investigations are relevant to diagnosing Chlamydia
Cervical / urethral / anal swab
Urine
Nucleic Acid Detection
Culture is not routine
Note: test of cure is required post-procedure and during pregancy screening
How is Chlamydia treated?
Azithromycin (1g oral x 2 doses one week apart) or Doxycycline ( 100mg oral bidaily 10-14 days -not to be used in pregnant women because the tetrocyclins stain the teeth of developing foetus)
In **severe chylamydia PID = **500mg Azithromycin IV daily 14 days
- Must contact trace partners
- Must be doctor notified
- Test-of-cure = 4-6 weeks
- Advise retest in 3 months
- Repeated episode of chlamydia can cause scarring of the infected regions
Characterise the **Trichomonas Vaginalis **microbe in STIs
Trichomonas Vaginalis is a flagellated protozoon that transmitted sexually
It is frequently asymptomatic - but when symptomatic it causes a characterisitc Frothy green-yellow vaginal discharge
**It is a marker of high risk sexual activity **and is associated with:
- greater rates of HIV acquisition
- non-steady sexual partner
- marijuana use
- elevated rates in indigenous communites
It causes cervical erythema & friability, pruritis, dysuria and abdominal pain
Testing =
- High vaginal swab + culture
- Urine - PCR
- Can be seen on Pap smears
Treatment =
- Metronidazole (not well tolerated due to metallic taste in mouth)
- Tinidazole
- Note: resistance development is increasingly common
*
What organism is responsible for the STI Symphilus?
Syphilis is caused by the spirochete bacteria Treponema Pallidum
Describe the disease course of syphilis
Syphilis is caused by the spirochete bacteria Treponema Pallidum
This microbe is innoculated onto genital organs through physical sexual contact
Infections can be asymptomatic but produce large numbers of transmissible organisms through replication that can eventually overcome host defences and cause symptomatic pathology.
There are three stages of syphilis infections:
Primary:
- dermatological pathology of the genital area (warts, abcesses etc)
Secondary:
- generalised illness develops (fever, weight loss, sore throat)
- whole body rashes, papules and nodules and allopecia
Tertiary:
- occurs 1 to 46 years after the initial infection, with an average of 15 years
-
formation of gummas
- can occur in any organ but most commonly aorta and joints
Is the incidence of reported syphilis on the decrease in Victoria?
No
Syphilis cases are on the increase - most natably among young males
Discuss the pro’s and con’s of various serological tests for syphilis
There are two classes of serological tests:
Non-treponemal tests (VDRL & RPR):
- are non-specific tests for syphilis
- involves Ab directed against T. pallaum cellular lipids and lecithin
- Useful for monitoring treatment efficacy
- Significant amount of false positive results; therefore not used as a screening or diagnostic test
- connective tissue disorders. viral infections, IVDU and pregnancy can also cause positive results
**Treponemal tests **(EIA, TPHA):
- Is a specific test for T.Pallidum
- Positive earlier than other class
- Positive results for life following a T. Pallidum infection
- useful for preventing progression of syphilis from latent infections
- Immunoblotting and PCR
When is an STI test indicated?
Symptomatic patient investigation
Screening for asymptomatic infections
Pre-pregnancy
Antenatal screening
Blood + Organ donation
Contact tracing
Epidemiological surveillance
