Sexually Transmitted Infections (STIs) Flashcards
What is an STI?
An infection spread by sexual contact
Those with sexual contact as the sole/predominant mode of transmission would cover chlamydia & gonorrhoea.
Those with other modes would include Hep A, B, C, and HIV
Not called STD because STIs are not always symptomatic.
What are some risk factors for STIs?
-Young age (especially <20yrs)
-Single
->2 partners in preceding 6/12
-Use of non-barrier contraception
-Residence in inner city
-Symptoms in partner
-Current STI & history of previous STIs
-Sexual orientation
-Chemsex
Summarise the main STIs and the pathogenic cause of each.
Bacterial:
-Chlamydia
-Gonorrhoea
-Syphilis
Viral:
-Genital herpes
-Genital warts
-HIV
Fungal:
-Candidiasis
Parasitic:
-Pediculosis Pubis
-Genital Scabies
What host defences does our body have and how do the microbes overcome them?
look at the slides
What is the causative organism in chlamydia and describe it?
Chlamydia trachomatis
It’s an obligate intracellular bacterium
Has extracellular (elementary body) and intracellular (reticulate body) forms
There are multiple serotypes of it, including A-K and L1, L2, & L3 (D-K are genital & L types are LGV)
Is chlamydia transmission common?
Yes, it’s the most common STI in the UK
Also congenital transmission is well-recognised, and that can also cause neonatal conjunctivitis in 30-50% of cases (and very rarely, you can get pneumonitis).
How does the chlamydia bacterium enter the body?
It binds to specific receptors and enters via parasite-specified endocytosis.
What are the signs and symptoms of chlamydia in females?
Symptoms:
-80% asymptomatic
-PV bleeding/purulent discharge/lower abdominal pain/dyspareunia/proctitis
Signs:
-Normal
-Cervicitis (discharge/contact bleeding)/adnexal tenderness
What are the signs and symptoms of chlamydia in males?
Symptoms:
-50% asymptomatic
-Urethral discharge/dysuria/testicular pain/proctitis
Signs:
-Normal
-Urethral discharge
What are some potential complications of chlamydia?
Female:
Ascending infection can lead to pelvic inflammatory disease (PID)
PID =endometritis/salpingitis/tubule damage/chronic pelvic pain
Increased risk of ectopic pregnancy (pregnancy outside the uterus) and infertility
Male:
Epididymitis
In either auto-inoculation may cause chlamydial conjunctivitis
How do you diagnose and treat chlamydia?
Diagnosis:
-Nucleic acid amplification testing (NAAT)
-High sensitivity and specificity for genital sites
-Also used for extra-genital sites (rectal/pharyngeal/ophthalmic)
Treatment:
-Azithromycin 1g STAT
-Doxycycline 100mg BD 7/7
What is the causative organism of gonorrhoea and describe it?
Neisseria gonorrhoea
Gram negative diplococci which are facultatively intracellular
By what method does the bacterium in gonorrhoea enter the body?
Site of entry = mucosal surfaces (vaginal / urethral / rectal)
Adhesive mechanism ensures it evades mechanical removal by secretions
Produces IgA protease to disable host secretory antibodies
Replicates in intracellular vacuoles which fuse with basement membrane releasing bacterium into connective tissue
Elicits host inflammatory response with resultant tissue damage
Can gonorrhoea be transmitted congenitally?
Yes and can result in neonatal conjunctivitis
What are the signs and symptoms of gonorrhoea in females?
Symptoms:
-70% asymptomatic
-Vaginal discharge
-Low abdominal or pelvic pain
Signs:
-Urethral discharge
-Cervicitis
-Cervical discharge
-Cervical excitation
What are the signs and symptoms of gonorrhoea in males?
Symptoms:
-85% with urethral infection develop symptoms in 10/7
-Commonly discharge or dysuria
-Rarely asymptomatic
Signs:
-Meatitis
-Urethral discharge
What are some extra-genital sites that can be affected by gonorrhoea?
-Conjunctivitis
-Pharyngitis
-Pharyngeal exudate
-Proctitis
-Rectal discharge
How do you diagnose and treat gonorrhoea?
Diagnosis:
-NAAT as per Chlamydia
-Due to resistance always perform culture and sensitivity
Treatment:
-Depends on local guidelines and resistance pattern
-Ceftriaxone 500mg IM STAT + –Azithromycin 1g PO STAT
What are some potential complications of gonorrhoea?
Female:
-Bartholinitis (inflammation of bartholin glands)
-Endometritis (Inflammation of endometrium)
-Salpingitis
-Peritonitis (inflammation of the peritoneum)
-Tubo-ovarian abscess
Male:
-Epididymitis
-Local abscess formation
Very rarely, it can disseminate further and cause septicaemia, arthritis, or skin lesions
What is the causative organism of syphilis and describe it?
Treponema pallidum
Motile spirochaete
How is syphilis transmitted?
Sexual contact
Can also be transmitted transplacentally (microbes from a pregnant woman’s bloodstream cross the placenta and enter the bloodstream of the fetus)
What are the stages of syphilis?
Primary, secondary, tertiary
Describe the features of primary syphilis.
10-90 days post-exposure
Develop papule at site of inoculation
Ulcerates and becomes painless, firm chancre
May go unnoticed (cervical/rectal ulcer)
Spontaneous resolution within 2-3 weeks
How do you treat syphilis?
Penicillin G, administered parenterally, is the preferred drug for treating persons in all stages of syphilis.
Dosage, and length of treatment depend on the stage and clinical manifestations of the disease.
Describe the features of secondary syphilis.
4-10 weeks
Constitutional symptoms (fever/sore throat/malaise/arthralgia)
Generalised lymphadenopathy
Generalised skin rashes (classically palms and soles)
Condylomata lata (warty, plaque-like lesions typically peri-anal region)
Superficial confluent ulceration of mucosal surfaces (‘snail track ulcers’)
Acute neurological signs (aseptic meningitis)
Without treatment, resolves after 3-12 weeks (gives false sense of security)
Describe the features of tertiary syphilis.
Years after inoculation
Gumma (granulomatous, ulcerating lesions) affecting skin typically at sites of trauma
Can affect bone and visceral organs
Cardiovascular manifestations (aorititis/aortic regurgitation)
Neurosyphilis also occurs (affecting nervous system)
How do you diagnose syphilis?
-Dark field microscopy (definitive diagnostic method)
Presumptive diagnosis of syphilis requires 2 tests:
-Treponemal specific
-Non-treponemal specific
What is the causative organism in genital herpes?
Herpes simplex virus (HSV) types 1 & 2 (both can infect mouth or genitals).
How is genital herpes transmitted?
-Close physical contact (sexual or oro-genital)
-Viral shedding by infected partner
-Sporadic (irregular), not necessarily associated with symptoms
What are the symptoms and signs of genital herpes?
-It’s variable
-You can get a severe primary episode within 2-12/7 of acquisition
-70-80% asymptomatic
What are potential complications of genital herpes?
Very rarely, you can get acute urinary retention/constipation /aseptic meningitis.
What can the first severe clinical episode (does NOT necessarily imply recent infection) of genital herpes include?
-Febrile illness (prodrome) 5-7 days
-Dysuria, urinary frequency
-Painful inguinal lymphadenopathy
-Tingling/neuropathic pain (genitals/buttocks/legs)
-Genital blisters, ulcers, fissures
-Untreated episode may last 3 weeks
What are some risk factors for genital herpes?
-Age (<20yrs)
-Severe 1st episode
-Occurs within 3 mths of 1° episode
-HSV type 2
-HIV or other immunodeficiency
What are the symptoms & signs of reactivated genital herpes?
-Recurrent episodes usually mild
-Neuropathic prodrome (tingling/burning)
-Erythema/blisters/fissures/ulcers
-Resolution within 3-4 days
How do you diagnose genital herpes?
Swab for HSV PCR (false negatives)
Do not delay treatment for results
Serology rarely performed
How do you treat primary genital herpes?
Usually settles within 5-7 days or beyond but new lesions
Aciclovir 200mg x5/day for 5-7 days
Analgesics/bathing in dilute saline solution/laxatives if required
How do you treat reactivated genital herpes or frequent/prolonged herpes?
Reactivation:
Analgesics/saline washes/petroleum jelly to lesions
Frequent/prolonged:
>6 episodes/yr or episodes last> 4 days at a time
Consider prophylactic therapy
What is the causative organism of genital warts and describe it?
Human papillomavirus (HPV)
-Over 80 types of which 30 associated with genital infection
-Most common 6, 11, 16, 18, 31 and 33
What is the incubation period for genital warts?
3-18mths (can be longer)
Frequently transmitted without presence of visible wart
How are genital warts transmitted?
-Close physical contact (skin to skin)
-Almost always genital for genital warts
-Auto-inoculation from other sites is rare
Where are genital warts commonly seen in males & females?
Female:
-Commonly in vulva/perianal region/cervix
-Less commonly in vagina/urethra
Male:
-Commonly penis/urethra/perianal region (regardless of sexual behaviour) /scrotum
What are the signs & symptoms of genital warts?
-Genital lumps (hard/soft, solitary/multiple)
-Bleeding (typically urethral)
-Itchiness
-Hyperpigmentation
How do you diagnose & treat genital warts?
Diagnosis:
-Clinical appearance
-Occasionally biopsy required
Treatment:
-Eradicate visible warts– NOT virus
-Podophyllotoxin cream for external warts
-Weekly cryotherapy
What are the complications of HPV?
12 HPV types, most high risk include: 16,18,31,45.
Linked to number of cancers
Strongest association with cervical cancer
What is the causative organism of HIV and describe it?
Human immunodeficiency virus
Member of lentovirus group of retrovirus family
Two types:
HIV-1 (most virulent)
HIV-2 (almost entirely West Africa)
What are the 3 major structural genes in HIV?
Gag- encodes nuclear proteins
Pol- encodes viral enzymes (reverse transcriptase, integrase, protease)
Env- encodes envelope glycoproteins
Describe the structural components of HIV and what they do.
look at the slides
What are the steps in HIV replication?
Viral replication:
- Complementary DNA (cDNA) strand produced from viral DNA by reverse transcriptase
- Second cDNA strand synthesised
- cDNA transported to cytoplasm
- Integrase cleaves cDNA and inserts into host genome
- Viral products transcribed by host cell
- Cleaved into proteins by HIV protease enzyme
- Assemble into new virus
- Virus buds from cell surface
What kind of immune responses do you get with HIV?
Humoral response:
B cells produce a ‘neutralising antibody’ against gp120 in all patients but this fails to clear the virus
Cytotoxic response:
Cytotoxic lymphocytes can control HIV replication in early infection but this is eventually overcome by progressive damage to the immune system
What is the natural history of HIV by primary infection (seroconversion)?
-60% develop symptoms of seroconversion (often mild)
-Usually 2-6 weeks after infection
-Diagnosis of primary is important
-May not be unwell again until late in infection
-Prevent onward transmission
-Treatment
What are some signs & symptoms of HIV infection?
-Fever
-Sore throat
-Malaise
-Arthralgia/myalgia
-Lymphadenopathy
-Oro-genital ulceration
-Rash
-Headache
-Diarrhoea
-Oral candida
Describe HIV classification:
Classified as A, B, or C
-lowest CD4 count determines the class
-Stay in that class even if CD4 levels begin to rise
Describe category C of HIV.
Much more unusual infections.
Describe categories A & B of HIV.
A:
-Persistent generalised lymphadenopathy
B:
-Candidiasis (oral)
-Herpes zoster involving min 2 episodes of more than one dermatome
-Oral hairy leukoplakia
What diagnosis and tests can you do to diagnose HIV?
- HIV antibody test:
-Standard test
-Can take up to 3mths to become positive - HIV p24 antigen (superseded by antibody test):
-Detects viral antigen rather than antibody - CD4 count (CD4 or helper T lymphocytes):
-Most useful indicator of current immune status
4.HIV load (viral load / HIV RNA):
-Current lower limit of detection <40 copies/ml (undetectable)
5.HIV genotype:
-Baseline as useful for choice of ART and then again after failure of ART
How can you treat HIV?
- Nucleoside Reverse Transcriptase Inhibitors:
-Mimic naturally occurring molecules
-Prevent attachment of next chain resulting in DNA breakage - Non-Nucleoside Reverse Transcriptase Inhibitors:
-Disparate group of drugs which fit into a molecular cleft, with reverse transcriptase which reduces catalytic activity - Protease Inhibitors:
-Inhibit the enzyme required for post-translational modification of viral gene products
4.Integrase Inhibitors:
-Block integration of HIV DNA into genome
- Co-receptor antagonists
What is the causative organism of genital candidiasis?
Candida albicans (80-90%)
Debatable as to whether its an STI or not
What is the risk of transmission of HIV post-exposure?
Risk of transmission= risk source of HIV x risk of exposure
When should you start HIV treatment?
The previous guidance was to start based on CD4 count <350 cells/microlitre but the current guidance is to start ART regardless of CD4 count.
What are the symptoms & signs of genital candidiasis?
Symptoms:
-Pruritis (itching)
-Discharge
-Burning sensation
Signs:
Female- erythema & vulval swelling; adherent white discharge
Male- erythema; discharge
What are some risk factors for genital candidiasis?
-Pregnancy
-Antibiotic therapy
-Diabetes mellitus
-Immunodeficiency (HIV/drugs/chemotherapy)
Is genital candidiasis an STI?
There is debate around the matter as to whether it is a pathogen at all or merely an overgrowth &
overdevelopment of the commensal organisms
The same argument is held in the oral cavity around oral candidiasis
How do you diagnose & treat genital candidiasis?
Diagnosis:
-Clinical
-Can be confirmed by microscopy and culture (+/- sensitivity)
Treatment:
-Topical- Clotrimazole 1% cream
-Systemic- Fluconazole 150mg STAT
What is the causative organism of pediculosis pubis (pubic lice)?
-Phythirus pubis
-This is distinct from other human lice
How is pediculosis pubis transmitted & what are the signs & symptoms?
-Transmitted by close bodily contact
-Symptoms & signs include itching
How do you diagnose & treat pediculosis pubis?
Diagnosis:
-Visualised on skin
-Nits (eggs) adhere tightly to pubic hair
-Highly characteristic under low-power microscope
Treatment:
-0.5% malathion
-1% permethrin
-Applied to entire body
-May require repeating after 1 week
What is the causative organism of genital scabies?
Mite- Sarcoptes scabiei
How is genital scabies transmitted?
Prolonged close contact (not isolated to sexual contact).
What are the symptoms & signs of genital scabies?
Symptoms:
Pruritis (worse at night)
Signs:
-Itchy, red papules (occasionally vesicles and pustules)
Can occur anywhere on skin (rarely face): web of fingers and toes; palms and soles; wrists and axilla; male genitalia; around nipples and umbilicus
Excoriations and 2° bacterial infections
How do you diagnose and treat genital scabies?
Diagnosis:
-Skin scraping
Treatment:
-0.5% malathion
-1% permethrin
-Applied to entire body
-May require repeating after 1 week
Pruritis often persists for up to 4 weeks post-treatment
What is important to consider when taking sexual history?
-Privacy
-Permission
-Do not make assumptions
-Use right terminology
How do you take a patient’s sexual history?
- History
- Presenting complaint
- History of presenting complaint:
-Male (discharge/sores/ulcers/dysuria/testicular pain/ED)
-Female (discharge/itching/pelvic pain/PV bleeding/dysuria/sores/ulcers/dyspareunia) - Partners:
-Sexually active/last sexual intercourse/contraception (barrier)/type of sex/regular or casual partner/no. of partners in last 3mths/same sex/overseas
What is the relevance of STDs to a dental practitioner?
Oral presentation- mainly HIV and syphilis diagnoses in unaware patients.
