22 Sexually transmitted infections Flashcards
Why are STIs cases increasing?
Estimated 500 000 new cases per year
Asymptomatic transmission Increasing density/ mobility of humans Change in human sexual practice Absence of vaccine Difficult to treat - resistant organisms
STI cases can occur with multiple infections. For example someone with syphilis, is more likely to ahve an additional STI
Which bacteria commonly cause STIs?
Chlamydia trachomatis
Haemophilus ducreyi (mainly tropical) - chancroid
Neisseria gonorrhoea
Treponema pallidum
What are treatments for these bacterial STIs?
Chlamydia trachomatis
- D-K serotypes cause urethritis
- L serotype - lymphogranuloma venereum
Haemophilus ducreyi (mainly tropical) - chancroid
Chlamydia trachomatis -
- azithromycin 1g single dose
- doxycycline 7 days
Haemophilus ducreyi - azithromycin, ceftriaxone
What are treatments for these bacterial STIs?
Neisseria gonorrhoea
Treponema pallidum
Neisseria gonorrhoea - ceftriaxone. Quinolone resistance common
Treponema pallidum - penicillin
Which viruses commonly cause STIs?
Papillomaviruses 6, 11, 16, 18 (warts/ cervical cancer)
HSV 1/2
HIV
Hepatitis B - transmitted sexually
What are treatments for these viral STIs?
Papillomaviruses 6, 11, 16, 18
HSV 1/2
Papillomaviruses - podophyllin, cryotherapy
HSV 1/2 - aciclovir, famciclovir
What are treatments for these fungal STIs?
Candida albicans - thrush
clotrimazole. fluconazole
Only one protozoa cause STIs.
What is treatment for Trichomonas vaginalis?
Often asymptomatic, can cause cancer
Metronidazole 2g single dose or
Metronidazole 400mg BD for 7 days
What are ectoparasite causes of STIs?
Sarcoptes sacbiei
Phthirus pubis
What are treatments for these ectoparasites?
Sarcoptes sacbiei
Phthirus pubis
Permethrin cream for both
How do STIs evade host defences?
- integrity of mucosal surface
- resist phagocytosis
- integrity of mucosal surface - have specific attachment mechanism e.g gonococcus/ chlamydia
- resist phagocytosis - induce little inflammation, or have capsule e.g treponema pallidum, gonococcus
How do STIs evade host defences?
- affect complement
- evade antibodies, especially IgA
- affect complement - C3d receptor on pathogen bins C3b/d and reduces phagocytosis e.g candida
- evade antibodies, especially IgA - produce IgA protease e.g gonococcus
How do STIs evade host defences?
- cell mediated immunity
- antigenetic variation allows re-infection with different strain e.g gonococcus/ chlamydia
What disease is caused by these spirochaetes ?
Treponema pallidum pallidum Treponema pallidum pertenue Treponema carateum Borrelia burgdorferi Borrelia recurrentis
Leptospira interrogans
Treponema pallidum pallidum - syphilis Treponema pallidum pertenue - yaws Treponema carateum - pinta Borrelia burgdorferi - lyme disease Borrelia recurrentis - relapsing fever
Leptospira interrogans - leptospirosis. Although this is a spiral organism, it is a leptospiraceae as opposed to spireochaetaceae
Syphilis enters the body through minute abrasions on skin or mucus membranes, and requires close contact. Organism does not survive outside body, and is sensitive to drying, heat, disinfectants.
Horizontal spread via sex
Vertical spread via transplancental
What is average incubation time?
What is length of latent period of syphilis?
3 weeks
3-30 years
What are stages of syphilis infection?
Primary infection - primary chancre - painless ulcer which heals spontaneously after 2 months. Lymphadenopathy. Teponemas multiply at site of infection/ lymph node
Secondary syphilis - flu like illness, myalgia, headache, fever, mucocutaenous rash. Resolves spontaneously
Latent syphilis - 3-30 years. Treponemas dormant in liver or spleen.
Tertiary syphilis - reawakening and multiplication of treponemas. Neurosyphilis, tabes dorsalis (demyelination of spinal cord), cardiovascular syphilis, heart failure. Gummas in skin, bone, testis
How does newborn present with congenital syphilis?
Intrauterine death
Congenital abnormalities - various
Silent infection - facial/ tooth deformities may only be seen by 2 years of age
T pallidum cannot be grown in vitro.
How is it diagnosed?
Dark field microscopy of exudate immediately after collection
Serology
Non-specific treponemal tests are
VDRL - veneral disease research laboratory
RPR - rapid plasma reagin test
How do they work and why are they non-specific?
Antigens are non-treponemal in origin
They are from extracts of cardiolipin from beef heart tissue, which allows detection of anti-lipid IgG/IgM formed in patient in response to lipoidal material released from cells damaged by infection (in addition to lipids on surface of T. Pallidum)
Non-specific syphilis tests are positive 1-2 weeks after primary chancre appears. Useful for initial screening test
Decline in positivity in tertitary syphilis or after treatment - can be used as vague indicator of treatment response.
What can cause false positive non-specific test? VDRL/ RPR
Acute febrile disease Collagen vascular disease Drug abuse Pregnancy Malaria Yaws/ Pinta Viral infection
Specific treponemal test use recombinant proteins/ treponemal antigens extracted from T. pallidum
What are examples of these?
Specific tests remain positive life-long. Therefore cannnot be used to assess treatment response
Enzyme immunoassay (ELISA) test. Checks for syphilis antibodies IgM/ IgG
FTA-ABS - fluorescnet treponemal antibody absorption. Non-pathogenic treponemes added to blood, to remove cross-reacting antibodies, before reacting with actual host T pallidum antigens
TP-PA - based on the agglutination of coloured particle carriers sensitized with T pallidum antigen
What can cause false positive specific treponemal tests?
AI disease- SLE DM Drug misuses Lyme disease Pregnancy Viral infections
Interpretation of spyhilis tests
Nontreponemal/Treponemal
\+ +
\+ –
– +
– –
Nontreponemal tests/ Treponemal tests
+ + Syphilis, yaws or pinta
+ – False positive – No syphilis
– + Primary or latent syphilis; previously treated or untreated syphilis; yaws or pinta
– – No syphilis; incubating syphilis
Babies born to infected mothers need to be tested. How to distinguish congenital infection, from passive transfer antibodies across planeta?
Test sypihlis IgM at birth, and 6 weeks age. Maternal antibodies will wane, and if still raised indicates cognenital syphilis
What is treatment for syphilis?
Penicillin - also treats unborn baby
Doxycycline - but can’t be used pregnancy
Screen for other STIs
Contact tracing
Gonorrhoea caused by neisseria gonorrhoea. Often asymptomatic, which facilitates its transmission.
How is it transmitted?
Rquires close contact, as very sensitive to drying.
Sexual
What unique characteristic help gonorrhoea evade host reponse?
Adhesive pili prevent being washed away. Can bind to epithelium of vagina, penis, rectum, oropharynx. Have constant/ variable regions (like immunoglobulins), so provides antigenic diversity
Capsule resists phagocytosis
IgA protease protects from host secretory antibodies
Invade non-ciliated epithelial cells, which allow bacteria to multiply in intracellular vacuoles. Vacuoles move down through cell and fuse with basement membrane, discharging content into connective tissues. Stimulates inflammatory process and damage
What symptoms does gonorrhoea cause?
Often asymptomatic - 50% women. Men more likely to be symptomatic
Dysuria
Urethral discharge
Vaginal discharge
Without diagnosis/ treatment - Pelvic inflammatory disease Infertility Opthalmia neonatorum Endocarditis Necrotic skin lesions - septic emboli Septic arthritis
How is gonorrhoea diagnosed?
Microscopy of exudate
Culture - resistance testing
What is treatment for gonorrhoea?
Ceftriaxone and azithromycin (this also treats chlamydia)
Resistance to penicillin/ fluorquinolones
What are the three difference chlamydia species, and what infections do they cause?
C trachomatis - trachoma, STI. Human natural host
C psitacci - pneumonia. Birds natural host
C pneumoniae - acute respiratory disease. Human natural host
Chlamydia trachomatis has three different groups, causing different diseases. What disease do these serotypes cause?
A, B, C
D-K
L1, L2, L3
A, B, C - trachoma
D-K - cervicitis, urethritis, conjunctivitis, pneumonia neonates
L1, L2, L3 - lymphogranuloma venereum
What is life cycle of chlamydia trachomatis?
Elementary body (EB) adapted for extracellular survival, binds to host receptor.
Endocytosis
Intracellular chlamydia differentiates intareticulate body, adapted for intracellular replication.
After replicaiton, some differentiate into EB, then released by cell to infect nearby cells
How is chlamydia diagnosed?
Direct fluorscent antibody test DFA - smear of specimen stained with fluorescein conjugated monoclonal antibodies, viewed by UV microscopy
Rapid molecular test
What is treatment of chlamydia infection?
Not susceptible to beta-lactams, which are used for gonorrhoea/syphilis. Which is why azithromycin is recommended when treating those conditions.
Azithromycin
Doxycycline
What are causes of inguinal lymphadenopathy?
Chancroid Donovanosis Gonorrhoea Lymphogranulonum venereum Syphilis
What causes lymphogranuloma venereum, and what is its geographical spread?
Chlamydia trachomatis L1, L2, L3
Africa/ Asia/ SA
Occasionally occurs in other continents
What clinical picture does LVG cause?
Primary ulcerating lesion at inguinal lymph nodes, which suppurates and discharge through skin
Can spread via lymphatics to cause systemic disease - fever, hepatitis, pnuemonitis, meningoencephalitis
Diagnosis of LVG
Treatment LVG
Cell culture
Immunofluorescence
Nucleic acid tests
Doxycycline
Erythromycin
Which bacteria causes chancroid?
What is clinical picture?
Haemophilus ducrei
Painful genital ulcers - as opposed to painless in syphilis
What is treatment of chancroid?
Azithromycin/ erythromycin
Ceftriaxone
Which bacteria causes donovanosis?
What is clinical picture?
Klebsiella granulomatis
Nodules on genitalia, which erode to form granulomatous ulcers that bleed on contact
How is donovanosis diagnosed?
What is treatment?
Smear examination for itnracellular donovan bodies in cytoplasm of mononuclear cells
Azithromycin
Doxycycline
Candida is normal commensal of vagina. At risk of infection if using oral contraceptivesm diabetes, antimicrobials, HIV.
How may it present if causing disease?
Irritant vaginitis
Cheesy vaginal discharge
Dysuria
How is candida diagnosed?
What is treatment?
Microscopy and culture
Topical - clotrimazole
Oral - fluconazole
Trichomonas vaginalis is protozoan parasite.
What is clinical picture?
Vaginitis with foul-smelling discharge
Men - often asymptomatic
How is trichomonas diagnosed?
Wet preparation of vaginal secretions
Nucleic acid detection tests (NAT) used if microscopy negative in suspected patients
What is treatment of trichomonas?
Metronidazole/ tinidazole
When there is significant increase in gardnerella vaginalis, changes to enviroment allow increase in obligate anaerobes such as bacterioides - causing bacterial vaginosis
What are clinical criteria for diagnosing bacterial vaginosis?
Excessive vaginal discharge
Fish-smelling discharge
Vaginal pH >4.5
Presence of clue cells - vaginal epithelial cells coated in bacteria give it a stippled appearance
What is treatment of bacterial vaginosis?
Metronidazole
HSV-2 is most common cause of genital herpes - usually transmitted sexually.
But HSV-1 being detected more frequently, although usually cause oropharyngeal infection, and cold sores
What is clinical picture?
Ulcers start as vesicles, which break down to form painful shallow ulcers
Local lymphadenopathy
Usually heals in 2 weeks. But virus can travel up sensory nerve endings to establish latent infection in dorsal root ganglion neurones. It can then reactivate - genital cold sores.
Aspeptic meningitis can occur
Spread from mother to infant at time of delivery can give rise to disseminated herpes or encephalitis
How is herpes diagnosed?
What is treatment?
HSV DNA from vesicle fluid or ulcer
Aciclovir
If recurrent - can take for 6-12 months, or take at start of symptom recurrence
HPV has over 120 different types.
Which types are associated with cervical cancer?
Which types are associated with genital warts?
16 + 18 + 31. highly infectious. 40% of females infected two years after starting sexual activity
6 + 11 cause genital warts
What is treatment of genital warts due to HPV?
What is treatment of cervical dysplasia due to HPV?
Podopyllin topically
Laser of loop excision
Which primarily GI infections, can be transmitted “opportunistically” as STI?
Particularly in HIV patient
CMV
HAV
HBV
Cryptosporidiosis
Giardia
Entamoeba histolytica
Shigella
Salmonella
Usually during oral-anal contact
What is treatment for pubic lice?
Permethrin cream
Malathion lotion
Scabies can affect genital region. What is treatment?
Permethrin cream
IVermectin if immunocompromised
What is differential diagnosis for vaginal discharge?
Candida Trichomonas Bacterial vaginosis Gardnerella Chlamydia Neisseria
Also consider foreign body, trauma, malignancy of cervix/ vagina, atrophic vaginitis
Who is targeed in HPV vaccination program?
12-13 year old females
Recently extended to MSM
Targets HPV 6/11/16/18
34 year old MSM presented with one dya history of painless ulcer on penis. Lesion firm and round. No rash, systemic symptoms or urethral discharge.
What is next test to perform?
Chlamydia NAAT Dark ground microscopy on swab from lesion Herpes simplex PCR Light microscopy from lesion RPR
Dark field microscopy - likely chancre from primary syphilis.
RPR may not detect antibody in early syphilis
HSV lesions likely to be painful, but important to sent swab for viral PCR
Chlamydia, particularly LGV serovars, can cause ulceration, but less likely
23 year old pregnant women presents 28 week gestation, with two day history of painful genital ulcers. No previous history of any similar lesions. Swab taken reveals HSV2 by PCR
What test is most useful to assess risk of transmission to baby?
HSV DNA load of lesion HSV DNA testing of blood HSV susceptibility test for aciclovir HSV antibody of her partner HSV antibody on her booking blood
HSV antibody on her booking blood
Greatest risk to baby if primary infection occurs to mother during late trimester. There will not be time for mother to develop antibodies, so baby will not receive enough passive maternal antibodies to resist infection.
Testing booking sample can help determine primary or secondary infection.
Mother should receive aciclovir therapy to suppress virus until delivery.
Obstetric team will inspect genital area for lesions at time of delivery. If present, will advise C-section
what are symptoms of congenital HSV2 infection?
Symptoms congenital -
- Localized skin infection–small, fluid-filled blisters on the skin and around the eyes and mouth that burst, crust over and heal
- Encephalitis–an inflammation of the brain, which can cause problems with brain and spinal cord function, including seizures
- Disseminated herpes infection–the most dangerous type of herpes infection. The herpes virus is spread throughout the body and can affect multiple organs, including the liver, brain, lungs and kidney.
Mycoplasma genitalium (MGen) is second most common cause of STI after chlamydia
What symptoms can it cause?
What are risks in pregnancy?
Often asymptomatic
Urethritis
PID
In pregnancy - risk transmission to baby linked to preterm birth and miscarriage?
How to diagnose mycoplasma genitalium?
Is not part of normal STI screen, despite being more common than gonorrhoea. If STI screen negative, and asymptomatic, then consider testing
- Vaginal swab
- First void urine sample
- If positive, should prompt investigation for other STI/ HIV and contact tracing
Not blood test for mycoplasma pneumoniae CFT
What is treatment for mycoplasma genitalium?
Doxycycline 100 mg twice daily for seven days
or
Azithromycin 1 g as a single dose, then 500 mg daily for two more days;
or
Moxifloxacin 400 mg daily for 10 days. This is currently reserved for cases known to be resistant to azithromycin. Resistance to moxifloxacin is already problematic in Asia.
Advise to refrain from sexual intercourse until finished treatment
Which STIs are associated with sero-negative arthrpathy?
Chlamydia - strongest association
Gonorrhoea
Mycoplasma genitalium
Shigella
