Treatment of UTI Co-infection with STI
When a urinary tract infection (UTI) occurs alongside a suspected sexually transmitted infection (STI), you must treat both conditions simultaneously with appropriate antimicrobial coverage for both uropathogens and sexually transmitted organisms.
Key Clinical Approach
Initial Diagnostic Strategy
- Obtain both urine culture AND nucleic acid amplification testing (NAAT) for gonorrhea and chlamydia before initiating treatment 1
- Perform urinalysis to document pyuria, but recognize that pyuria occurs in 37% of STI cases, with 74% having sterile pyuria (negative urine cultures despite white blood cells) 2
- Do not rely on abnormal urinalysis findings alone - they have only 41% positive predictive value for true UTI in the setting of STI 3
- Gram stain of urethral discharge can provide preliminary diagnosis of gonococcal urethritis 1
Critical Pitfall to Avoid
Overdiagnosis of UTI and underdiagnosis of STI is extremely common - studies show 48% of women diagnosed with UTI in emergency departments actually had negative urine cultures, while 37% of women with confirmed STIs were not treated for their STI because they were misdiagnosed with UTI instead 3. This leads to unnecessary antibiotic exposure and missed STI treatment.
Treatment Regimen for Co-infection
For Confirmed or Suspected STI Component
Treat empirically for both gonorrhea and chlamydia 1:
Alternative regimens if first-line agents cannot be used 1:
- Levofloxacin 500 mg orally once daily for 7 days
- Ofloxacin 300 mg orally twice daily for 7 days
- Erythromycin base 500 mg orally four times daily for 7 days
For UTI Component
The treatment depends on whether this is uncomplicated or complicated UTI:
Uncomplicated UTI (otherwise healthy, non-pregnant females)
First-line options 5:
- Nitrofurantoin for 5 days
- Fosfomycin tromethamine 3 g single dose
Second-line options 5:
- Fluoroquinolones (ciprofloxacin or levofloxacin) - only if local resistance <10% 1
- Amoxicillin-clavulanate
Complicated UTI (males, anatomic abnormalities, immunosuppression, healthcare-associated)
For patients requiring hospitalization or with systemic symptoms 1:
- Amoxicillin plus aminoglycoside (strong recommendation)
- Second-generation cephalosporin plus aminoglycoside (strong recommendation)
- Intravenous third-generation cephalosporin (strong recommendation)
Treatment duration: 7-14 days (14 days for men when prostatitis cannot be excluded) 1
Specific Considerations
When to Treat Empirically Without Waiting for Culture Results
- High-risk patients unlikely to return for follow-up should receive empiric treatment for both gonorrhea and chlamydia 1
- Severe urethritis warrants immediate empiric treatment 1
- Mild symptoms allow delaying treatment until NAAT results are available 1
Fluoroquinolone Restrictions
Do not use fluoroquinolones empirically 1:
- In patients from urology departments
- When patients have used fluoroquinolones in the last 6 months
- When local resistance rates exceed 10%
This is critical because fluoroquinolones are needed for both UTI and STI treatment, but resistance patterns and antimicrobial stewardship principles limit their use 6.
Partner Management
All sexual partners within the preceding 60 days must be evaluated and treated 1. Patient confidentiality must be maintained while ensuring partners receive appropriate treatment 1.
Follow-up Requirements
- Patients should abstain from sexual intercourse until 7 days after therapy initiation and symptoms have resolved 1
- All patients diagnosed with new STI should receive testing for other STDs, including syphilis and HIV 1
- Retest for gonorrhea and chlamydia 4-6 weeks after completing therapy 1
Managing Complicating Factors
Address any underlying urological abnormality - this is mandatory for successful treatment of complicated UTI 1. Common complicating factors include obstruction, foreign bodies, incomplete voiding, vesicoureteral reflux, recent instrumentation, diabetes, and immunosuppression 1.