STIs Flashcards
What does Molluscum contagiosum cause?
Viral skin infection (DNA pox virus) —> causes firm, smooth, umbilicated papules (central depression on small swelling of skin) ~2-5mm in diameter
?sexually transmitted (occurs in children therefore is primarily non-sexually transmitted)
Children = trunk/extremities Adults = lower abdomen, inner thighs, genitals
What are the groups at risk of STIs?
- young people
- certain ethnicities (affects type of STI): white & Asian = genital warts and Black & Mixed = genital warts & gonorrhoea
- low socio-economic status groups
- age at 1st intercourse, no. of partners, sexual orientation (particularly MSM - syphilis & gonorrhoea), unsafe sexual activity
- females aged 15-25yrs have high incidence of chlamydia
Give some reasons for the increased incidence of STIs.
- increased transmission due to changes in sexual/social behaviour e.g. post-war, 60s & oral contraceptive pill, HIV epidemic and increased density/mobility of populations
- increased GUM attendance (reduced stigma)
- greater public/medical/national awareness e.g. chlamydia screening campaign
- improved diagnostic methods of screening programmes
What are some factors contributing to the medical burden of STIs?
- acute & chronic/relapsing infections
- stigma: impacts on diagnosis & tracing sexual contacts
- consequences: PID, infertility, reproductive tract cancers, disseminated infections, transmission to foetus/neonate
Outline the general management of STIs.
Treatment preferably single dose (reduces resistance)
Co-infections are common therefore screen for other STIs & consider empiric treatment
Contact tracing
Sexual health education, advice on contraception, detailed instruction on practice & need for safer sex
Contrast sexually transmitted infections and sexually transmitted diseases.
Sexually transmitted infection (STI) = any infection transmitted through sexual activity
- sexual activity is the principal mode of transmission but does not have to be exclusive e.g. blood-borne viruses
- includes asymptomatic & symptomatic cases
Sexually transmitted disease = infectious disease transmitted via sexual activity
- only includes symptomatic cases
note: it is possible for intestinal pathogens to be sexually transmitted, particularly in MSM e.g. Salmonella, Shigella, Giardia, Entamoeba
(gastrointestinal opportunistic infections)
note: non-specific genital infections include: HIV new diagnoses, scabies, trichomoniasis, chancroid, pediculosis pubis, Molluscum contagiosum
Outline the types of HPV. How is it diagnosed, treated, and screened for?
DNA virus, 100+ types
Most common viral STI (~4% of young adults)
HPV 6 & 11:
- cause cutaneous, mucosal, & anogenital warts
- benign and painless (verrucous epithelial/mucosal outgrowths)
- warts can present on penis, vulva, vagina, urethra, cervix, perianal skin
HPV 16 & 18 = oncogenic types associated with cervical cancer (70%+ - most common cancer in women aged 15-34yrs) & anogenital cancer
Diagnosis = biopsy + genome analysis, hybrid capture
Treatment:
- none; sponataneously resolves (70% in 1yr, 90% in 2yrs)
- persistent = topical podophyllin, cryotherapy, intralesional interferon, imiquimocl, surgery
Screening: cervical pap smear cytology & cervical swab for HPV hybrid capture
—> abnormal result —> colposcopy (look at cervix using microscope with bright light) with acetowhite test (stains abnormal areas white - acetowhite lesions)
Vaccine: offered to girls aged 12-13yrs (ideally before sexual activity has started); 2 doses, 99% effective in preventing HPV 16 & 18 - related cervical abnormalities (in those not already affected)
- Cervarix (HPV 16 & 18 - oncogenic types only) = used initially in the UK
- Gordasil (HPV 6, 11, 16, 18 - oncogenic & non-oncogenic types) = used from 2011 onwards
Outline the presentation of chlamydia infection. How is it diagnosed, treated, and screened for?
Chlamydia trachomatis (differentiate from chlamydia-related respiratory infections) = non-specific genital chlamydial infections (serotypes D-K)
note: often asymptomatic
Males: urethritis, epididymitis, prostatitis, proctitis +/- discharge
Females: urethritis, cervicitis, salpingitis, perihepatitis (causes RUQ pain referred to shoulder tip due to inflammation of liver capsule/diaphragm —> Fitz-Hugh-Curtis syndrome) +/- discharge
+ ocular inoculation-conjunctivitis
+ neonatal infections = inclusion conjunctivitis, pneumonia, opthalmia neonatorum (any conjunctivitis in the first 28 days after birth)
Diagnosis: nucleic acid amplification test (NAAT) - does not have to be symptomatic & can test for N. gonorrhoeae at same time
- endocervical & urethral swabs (female)
- 1st void urine (male & female)
- (conjunctival swabs)
Treatment: doxycycline or azithromycin
(erythromycin in children)
Screening: 50% of all cases detected via screening programme (targets sexually active under 25yrs)
- necessary due to causing PID, ectopic pregnancy, fertility problems
Outline the types of herpes virus. How is it diagnosed and treated?
Herpes simplex virus:
- cold sores (HSV1)
- genital herpes (HSV2)
- herpetic Whitlow = on terminal phalanx of fingers (very painful; 60% HSV1)
PRIMARY:
- extensive painful genital ulceration
- dysuria
- inguinal lymphadenopathy
- fever
RECURRENT: latent infection in dorsal root ganglia
- asymptomatic —> moderate
- risk of transmission during pregnancy (affects decision of delivery method)
Diagnosis: PCR of vesicle fluid/ulcer base
Treatment:
- aciclovir
- prophylaxis might be required for freq. recurrences
- barrier contraception to reduce risk of transmission
Outline the features of gonorrhoea infection. How is it diagnosed and treated?
Neisseria gonorrhoeae = Gram-ve intracellular diplococcus
Males: urethritis, epididymitis, prostatitis, proctitis, pharyngitis +/- discharge (depends on sexual practices)
Females: asymptomatic, endocervicitis, urethritis, PID (may lead to infertility)
+ disseminated gonococcal infection (particularly in young females) —–> bacteraemia, skin lesions, joint lesions
Diagnosis:
- swab from urethra, cervix, (+ throat, rectum)
- urine (NAAT)
note: Gram stain can be done on pus (fairly reliable) or on a normally sterile site (more specific identification needed & special media required)
Treatment: IM ceftriaxone + azithromycin (test/treat for chlamydia, prevents emergence of cephalosporin-resistant strains)
Outline the features of syphilis infection. How is it diagnosed and treated?
Treponema pallidum = spirochete
Most cases MSM and commercial sex workers
PRIMARY: indurated, painless ulcer (chancre)
SECONDARY (6-8wks later): chancre disappears, fever, rash, lymphadenopathy, mucosal lesions
LATENT: asymptomatic (years)
TERTIARY:
- neurosyphilis (tabes dorsalis/syphilitic myelopathy = slow demyelination of nerves in dorsal columns of spinal cord, chronic meningoencephalitis —> cerebral atrophy —> general paresis/paralytic dementia)
- cardiovascular syphilis (myocarditis, coronary stenosis, aortic aneurysm, aortitis, aortic insufficiency)
- gummas (soft, non-cancerous growth which causes local destruction)
CONGENITAL
Diagnosis: cannot be grown!
- dark-field microscopy
- serology: initial screening with EIA antibody test, positive result leads to rapid plasma reagin titre (non-specific; cross-reaching antigen) & TP particle agglutination (specific)
Treatment: penicillin + refer to GUM/infectious diseases
Give some examples of less common tropical STIs which can cause inguinal lymphadenopathy.
Lymphogranuloma venereum =
- C. trachomatis L1, L2, L3
- usually MSM
- rapidly healing papule —> inguinal bubo
Chancroid =
- Haemophilus ducreyi
- painful genital ulcer (differentiates from chancre)
Granuloma inguinale =
- Klebsiella granulomatis
- genital nodules —> ulcers
What is trichomonas vaginalis? How is it diagnosed and treated?
Trichomonas vaginalis = flagellated protozoan —> trichomonas vaginitis
Predominantly sexually transmitted
S&S:
- thin, frothy, offensive discharge
- irritation
- dysuria
- vaginal inflammation
Diagnosis = vaginal wet preparation +/- culture enhancement
Treatment = metronidazole (anaerobes & some protozoa)
What is vulvovaginal candidiasis? How is it diagnosed and treated?
Thrush = Candida albicans + other Candida spp.
- sexually transmitted, nappy rash, opportunistic
- risk factors: antibiotics, oral contraceptive pill, pregnancy, obesity, steroids, diabetes
S&S: profuse, white, itchy, curd-like discharge
Diagnosis: high vaginal smear +/- culture
Treatment:
- topical azoles
- nystatin
- oral fluconazole
What are the most common causes of vaginal discharge?
Trichomonas vaginalis
Vulvovaginal candidiasis
Bacterial vaginosis
note: as treatment is the same, often little point in specific investigations
What is bacterial vaginosis? How is it diagnosed and treated?
Overgrowth of anaerobes, mycoplasmas (perturbed normal flora)
- has effects in pregnancy
S&S: scant but offensive fishy discharge
Diagnosis:
- vaginal pH > 5
- KOH whiff test (add KOH to sample —> amine smell)
- HVS Gram stained smear showing absence of pus cells, reduced no. of lactobacilli, and presence of “clue cells” (epithelial cells studded with Gram variable coccobacilli)
Treatment: metronidazole
What is scabies? How does it present?
Sarcoptes scabiei (mite)
Contagious skin infection; present all over body but can affect genitalia and be spread sexually.
S&S:
- itching
- rashes (hands, feet, wrists, elbows, back, buttocks, external genitalia)
What is pubic lice? What is crabs?
Pubic lice = Pediculosis pubis
Crabs = Phthirus pubis
Only affects pubic hair, distinct from other human body lice
What are some of the consequences of uterine tube infection?
Infertility due to scarring & damage
Increased risk of ectopic pregnancy
Both caused by adhesions preventing ova from entering the uterus
What are the differential diagnoses for painful genital ulcers?
Herpes simplex virus (usually HSV2)
Haemophilus ducreyi (tropical STI —> chancroid)
Klebsiella granulomatis (tropical STI —> granuloma inguinale)
Treponema pallidum (syphilis, but lesions rarely multiple)
Behcet’s syndrome or erythema multiforme
