Sexually Transmitted Infections & Related Conditions — Key Points

General Principles

• STIs are often asymptomatic but can still be transmitted and cause serious future complications.
• They disproportionately affect younger people, though increasingly identified in older adults where diagnosis is often missed.
• One STI found = screen for all others (coexistence is common).
• Modern testing uses multiplex NAATs (nucleic acid amplification tests) — highly sensitive, can detect multiple infections from a single swab/urine sample, including self-taken samples.
• Point-of-care tests exist for HIV and others but have suboptimal sensitivity/specificity.
• Confidentiality and partner notification are critical — partners require simultaneous testing and treatment.
• Always consider safeguarding: screen for sexual exploitation, coercion, domestic abuse, especially in those under 16.

Taking a Sexual History

• Reason for attendance and symptoms
• Past/current STI history including HIV status
• Sexual partners in the last 3 months, gender, country of origin, condom use, symptoms
• Any forced sex, violence, abuse, or coercion
• For under 16s: age of partner, whether they attend school, family support, safeguarding assessment
• Capacity assessment is mandatory for under 16s without parental consent

Caring for Transgender & Non-Binary Individuals

• Use preferred pronouns and name
• Establish current anatomy, hormone use, and type of sexual activity to guide testing
• Offer appropriate contraception, STI screening, HPV vaccination, HIV prevention, and cervical screening based on anatomy

Infective Causes of Vaginal Discharge

Bacterial Vaginosis (BV)

• Not classified as an STI, but associated with sexual activity
• Caused by depletion of lactobacilli → pH rises >4.5; overgrowth of Gardnerella vaginalis and anaerobes
• Diagnosis (Amsel criteria): homogeneous discharge + high pH + clue cells on microscopy + fishy odour with 10% KOH
• Complications: PID, post-hysterectomy cuff cellulitis, preterm birth, miscarriage
• Treatment: oral or intravaginal metronidazole or clindamycin (treat if symptomatic or pre-surgery); partners do NOT need treatment
• Avoid vaginal douching

Vulvovaginal Candidiasis

• Caused by Candida albicans (most common)
• Not an STI — partners without symptoms do not need treatment
• More frequent/persistent in diabetes, immunocompromise, pregnancy
• Diagnosis: microscopy and culture (swab)
• Treatment: topical intravaginal pessaries or oral imidazoles; topical vulval antifungals for symptomatic relief

Trichomoniasis

• Caused by flagellate protozoan Trichomonas vaginalis — is an STI
• Often causes vaginal discharge ± signs of vulvovaginitis; asymptomatic colonisation in up to 50%
• Associated with preterm birth, low birth weight, maternal postpartum sepsis
• Gold standard diagnosis: NAAT (vulvovaginal swab); also culture or wet mount (lower sensitivity)
• Treatment: systemic metronidazole — simultaneous treatment of current sexual partners required

Cervicitis

Gonorrhoea (Neisseria gonorrhoeae)

• Endocervical infection asymptomatic in up to 50%
• Symptoms: altered vaginal discharge, lower abdominal pain (~25%)
• Rectal infection via anal sex; pharyngeal infection via oral sex (nearly always asymptomatic)
• Ascending infection → PID; rarely → disseminated gonococcal infection (purpuric non-blanching rash + monoarticular arthritis)
• Neonatal conjunctivitis if mother infected at delivery
• Diagnosis: NAAT (vulvovaginal swab); culture required if tested positive before treatment (surveillance for antimicrobial resistance)
• ⚠️ Widespread antimicrobial resistance — requires surveillance
• Treatment: parenteral third-generation cephalosporin (first-line)

Chlamydia (Chlamydia trachomatis)

• Most common bacterial STI; often asymptomatic but causes subclinical PID and complications
• Symptoms: altered vaginal discharge, intermenstrual/post-coital bleeding, abdominal pain; cervicitis may be present
• Can cause reactive monoarthritis (more common in men); neonatal conjunctivitis
• Diagnosis: NAAT (vulvovaginal swab, self-taken)
• Treatment:
  • Non-pregnant: doxycycline
  • Pregnant: azithromycin + test of cure
  • Partner treatment simultaneously required

Mycoplasma genitalium

• Causes cervicitis, endometritis, PID
• Test with vulvovaginal swabs including macrolide resistance testing where possible
• Treatment: doxycycline → azithromycin → moxifloxacin (escalating regimen based on resistance)

Pelvic Inflammatory Disease (PID)

• Ascending infection from endocervix to upper reproductive tract
• Caused by chlamydia, M. genitalium, gonorrhoea, or normal vaginal flora
• Diagnosis is clinical: bilateral lower abdominal pain, dyspareunia, altered vaginal discharge, intermenstrual/post-coital bleeding + cervical motion tenderness + cervicitis
• Always exclude pregnancy; test for all STIs
• Start empirical treatment immediately — delay increases risk of complications
• Complications: subfertility, ectopic pregnancy, chronic pelvic pain, Fitz-Hugh–Curtis syndrome (perihepatitis with "violin string" perihepatic adhesions → right upper quadrant pain)
• IUD: consider removal if not responding to treatment (weigh against pregnancy risk if recent unprotected sex)
• Treatment: 2-week course — macrolide or tetracycline + metronidazole + initial parenteral third-generation cephalosporin
• Partners require simultaneous screening and empirical treatment

Viral STIs

Genital Herpes (HSV)

• Caused by HSV-1 (also orolabial) and HSV-2 — both cause genital herpes
• Latency in sensory ganglia → reactivation with or without symptoms; asymptomatic shedding is a key transmission route
• Recurrence higher with HSV-2; decreases in frequency over time
• Symptoms: genital pain, dysuria, vesicular ulcers
• Pregnancy risks:
  • Primary infection in third trimester → neonatal infection rate up to 41%
  • Recurrent infection at delivery → neonatal herpes risk <3% (maternal IgG crosses placenta)
  • Primary herpes in third trimester → elective pre-labour caesarean section
  • Proven recurrent lesions → vaginal birth may be anticipated
• Treatment: aciclovir (safe and effective; episodic or suppressive regimens)

Genital Warts & HPV

• Warts: benign epithelial tumours caused by HPV types 6 and 11 (~90% of genital warts)
• Oncogenic types 16 and 18 cause ~70% of cervical cancer + other HPV-related cancers (oropharyngeal, penile, anal, vaginal, vulval)
• Most genital HPV infections are subclinical
• HPV vaccination available — highly effective for prevention
• Diagnosis of warts: clinical examination
• Treatment options (optional for benign warts):
  • Ablative: liquid nitrogen, surgical techniques
  • Topical patient-applied: podophyllotoxin or imiquimod
  • In pregnancy: ablative therapies only
• Rarely, large warts obstruct birth canal → caesarean section needed
• Very rarely: neonatal respiratory papillomatosis (caesarean benefit unproven)

Syphilis (Treponema pallidum)

• Transmitted by direct contact with infective lesions or transplacental passage
• Multisystem disease — frequently misdiagnosed as it mimics many conditions
• Untreated: relapse/remit with late complications appearing years later

Stages of Acquired Syphilis:

• Infectivity declines with time; penicillin-based regimens are curative (reinfection possible)
• Resurgence in gay/bisexual MSM and in pregnant women in recent decades

Congenital Syphilis:

• Screen all pregnant women — riskiest period is infection just before or during pregnancy
• "Negative now" message — women screened early should re-screen if at risk later
• Early congenital features (within 2 years): rash, haemorrhagic rhinitis ("bloody snuffles"), lymphadenopathy/hepatosplenomegaly, skeletal abnormalities, condylomata lata, pseudoparalysis, non-immune hydrops, glomerulonephritis, haemolysis
• Late congenital "stigmata": Hutchinson's incisors, mulberry molars, interstitial keratitis, Clutton joints, saddle nose, sensorineural deafness, frontal bossing, intellectual disability

Diagnosis:

• Serology: treponemal test (EIA) → confirm with second treponemal test + non-treponemal titre
• Can be negative in very early disease → repeat 4–6 weeks later if suspected
• Serological tests usually positive for life even after curative treatment

HIV

Natural History & Epidemiology

• Acute viral illness → chronic depletion of CD4+ T-lymphocytes → AIDS-defining illnesses
• AIDS-defining illnesses include: invasive cervical cancer, PCP, CMV disease, Mycobacterium tuberculosis, recurrent bacterial infections, CNS lymphoma, Kaposi's sarcoma, and many others
• Cervical pre-cancer is an HIV indicator condition (prevalence of undiagnosed HIV >0.1%)
• Disproportionately affects: sub-Saharan Africans, gay/bisexual MSM, intravenous drug users
• HAART has transformed outcomes — new diagnoses falling globally (>30% worldwide)

Testing

• Recommended for all with AIDS-defining/HIV indicator conditions
• Routine screening in high-prevalence populations (UK: areas >0.2% prevalence, ages 15–59)
• All pregnant women must be screened

Gynaecological Complications

• HIV+ women have higher risk of persistent oncogenic HPV, higher CIN/HSIL incidence → annual cervical screening recommended
• Higher risk of all anogenital HPV-related malignancies, at younger ages

HIV in Pregnancy — Management

1. Confirm HIV status in all pregnant women
2. Effective HAART → achieve undetectable viral load (VL)
3. Most vertical transmission occurs during birth or breastfeeding; intrauterine infection unusual (increased risk with amniocentesis)
4. Pre-labour caesarean section if VL is detectable
5. Avoid: prolonged rupture of membranes, fetal scalp electrodes, procedures that breach infant's skin
6. Breastfeeding: formula feeding preferred if safe; if breastfeeding chosen (with good VL control):
   • Exclusive breast milk, rapid weaning, no mixed feeding
   • Do not feed from breast with mastitis or cracked nipples
   • Monthly VL monitoring for mother and infant
7. With optimal management, vertical transmission rates are extremely low

Contraception

• Many antiretrovirals interact with hormonal contraceptives (reduced efficacy) — check the University of Liverpool HIV Drug Interactions tool
• Non-hormonal contraception (condoms, IUDs) appropriate in most cases

Preconception

• For sero-discordant couples: undetectable VL eliminates sexual transmission
• Screen and treat coexistent STIs
• Fertility treatment is appropriate within regulatory frameworks

Recommended Guidelines & Resources

• BASHH guidelines (British Association for Sexual Health and HIV)
• BHIVA guidelines (British HIV Association)
• CDC STI treatment guidelines
• University of Liverpool HIV Drug Interactions