Sexually Tract Infections (STIs)

STI Differentials

STI Tips

Male Urethritis

Disease Diagnosis Treatment Follow-Up
Gonorrhea Urine NAAT Ceftriaxone 250mg IM x1 + Azithromycin 1g PO x1
Substitute gemifloxacin 320mg PO x1 or gentamicin 240mg IM x1 if cephalosporins contraindicated
Abstain from sexual contact x7 days
Repeat test in 3-4mo
Test prior partners within past 60 days
Chlamydia Azithromycin 1g PO x1
Doxycycline 100mg PO BID x7 days
Erythromycin 500mg PO QID x7 days
Levofloxacin 500mg PO daily x7 days
Ofloxacin 300mg PO BID x7 days
Mycoplasma Difficult to diagnosis
Suspect if persistent/recurrent urethritis
Azithromycin 1g PO
If fails, moxifloxacin 400mg daily x7-14 days
Abstain from sex until symptoms resolve and treatment completed
test prior partners within past 60 days

Genital Ulcers

Disease # Ulcers Painful? Lymphadenopathy? Diagnosis Treatment
Treponema pallidum
Single No Regional Nontreponemal (sensitive): VDRL, RPR
Treponemal (specific): FTA-ABS, EIAs
Benzathine penicillin G 2.4 million U IM x1
Doxycycline 100mg PO BID x14 days
Tetracycline 500mg PO QID x14 days
Other treatments for tertiary syphilis
Multiple Yes Painful bilateral Cell culture + PCR (swab ulcer base) Acyclovir 400mg PO TID x7-10 days
Acyclovir 200mg PO x5 x7-10 days
Valacyclovir 1g PO BID x7-10 days
Famciclovir 250mg PO TID x7-10 days
Other regimens for recurrent episodes
Haemophilus ducreyi
Multiple, raw Yes Unilateral and painful (50%)
may become fluctuant and rupture
1+ painful genital ulcers + typical chancroid appearance + negative syphilis and HSV tests Azithromycin 1g PO x1
Ceftriaxone 250mg IM x1
Ciprofloxacin 500mg PO BID x3 days
Erythromycin 500mg PO TID x7 days
Granuloma inguinale
Klebsiella granulomatosis
Multiple, friable No None Send-out test Azithromycin 1g PO qWeek
500mg PO qDay x3 weeks
Consider biopsy if no resolution
Lymphgranuloma Venereum
C. trachomatis serovars L1-3
Single No Painful and unilateral NAAT available Doxycycline 100mg PO BID x21 days
Erythromycin 500mg PO QID x21 days
Molluscum contagiosum
Multiple No No Based on clinical picture Observation
Avoid auto-inoculation
Local therapies

MPox (from Lee 2023)




  • Candidal vaginitis risk factors: pregnancy, immunocompromised, DM, contraceptives, recent antibiotic use
  • Candidiasis management: fluconazole 150mg PO x1 or topical therapies x7-14d, refer to gynecology if recurrent vaginitis or other complicating factors
  • Bacterial vaginosis: most common cause of discharge, increased risk with new/multiple sexual partners, gold standard diagnosis with Gram stain (but can use Amsel criteria, see below), culture not recommended
  • Amsel criteria (need 3 of 4): homogenous white discharge covering vaginal walls, clue cells on microscopic examination, pH > 4.5, positive whiff test
  • Differential

    Diagnosis Discharge pH Microscopy Symptoms Treatment Treat partner?
    Normal discharge White, thick, smooth ≤ 4.5 Lactobacilli - - -
    Candidiasis (C. albicans) White, thick, curdlike Mycelia Itching, dysuria Topical therapies
    Fluconazole 150mg PO x1
    Persistent/recurrent infections may require alternate treatments for non-C. albicans
    Only if balanitis present
    Trichomoniasis Frothy, purulent ≥ 4.5 Trichomonads, WBC Vulvar erythema/edema Metronidazole 2g PO x1 (5% resistance rate)
    Tinidazole 2g PO x1
    Bacterial vaginosis Thin, white Absent lactobacilli, clue cells, amine odor Increased discharge, odor Metronidazole 500mg PO BID x7 days
    Metronidazole gel 0.75% intravaginally daily x5 days
    Clindamycin 2% cream intravaginally QHS x7 days

    HPV and HIV

    Human papillomavirus(HPV)

    Human immunodeficiency virus