What is the treatment for a 22-year-old female with fever, nausea, and vomiting, diagnosed with a urinary tract infection (UTI) caused by Viridans streptococcus, with greater than 100,000 colony-forming units per milliliter (CFU/mL) on urine culture?

Treatment of Viridans Streptococcus UTI in a 22-Year-Old Female

This patient requires empiric treatment with amoxicillin or ampicillin as first-line therapy, given that Viridans streptococci are typically susceptible to penicillins, and this represents a complicated UTI requiring systemic antibiotic therapy for 7-10 days.

Clinical Context and Classification

This presentation represents a complicated UTI rather than simple cystitis, based on:

• Systemic symptoms (fever, nausea, vomiting) suggesting upper tract involvement or systemic infection 1
• High colony count (>100,000 CFU/mL) of an atypical organism 1
• Viridans streptococci are uncommon urinary pathogens and their presence warrants investigation for underlying urological abnormalities 2

The presence of fever with nausea and vomiting indicates this is not simple cystitis but likely represents pyelonephritis or complicated lower UTI requiring more aggressive management 1.

Recommended Antibiotic Regimen

Primary treatment options:

• Amoxicillin 500 mg PO/IV every 8 hours for 7-10 days 1
• High-dose ampicillin 18-30 g IV daily in divided doses (if severe presentation or hospitalized) 1
• Penicillin G (alternative if amoxicillin unavailable)

Rationale: Viridans streptococci are gram-positive organisms that are typically highly susceptible to penicillins 3. While the laboratory notes susceptibility testing is not routinely performed, these organisms generally retain excellent susceptibility to beta-lactam antibiotics 4.

Treatment Duration and Route

• Duration: 7-10 days minimum given systemic symptoms 1, 4
• Route: Given fever and gastrointestinal symptoms (nausea/vomiting), consider starting with IV therapy until symptoms improve, then transition to oral 1
• For outpatient management with mild symptoms, oral amoxicillin is acceptable if the patient can tolerate oral intake 1

Critical Management Considerations

This case requires urological investigation because:

• UTIs caused by atypical organisms like Viridans streptococci are frequently associated with underlying renal-urological abnormalities (70% of cases in literature review) 2
• The presence of non-E. coli organisms, particularly gram-positive cocci, should prompt evaluation for structural abnormalities 1, 5
• Obtain renal and bladder ultrasound to evaluate for hydronephrosis, stones, anatomical abnormalities, or other predisposing factors 1

Imaging should be performed:

• After clinical improvement and completion of antibiotic therapy (3-6 weeks post-treatment) 4
• Earlier imaging (within 72 hours) if patient fails to improve or worsens clinically 1

Common Pitfalls to Avoid

Do not dismiss this as simple cystitis despite the patient's young age—the combination of systemic symptoms and atypical organism mandates treatment as complicated UTI 5.

Do not use nitrofurantoin or fosfomycin as these agents:

• Are only appropriate for uncomplicated lower UTI 1
• Have insufficient tissue penetration for upper tract or complicated infections 1
• Are not reliably active against streptococcal species 1

Do not use fluoroquinolones or cephalosporins as first-line when penicillins are the preferred agents for streptococcal infections and have superior efficacy 1, 4.

Follow-Up Requirements

• Urine culture should be repeated if symptoms do not resolve within 48-72 hours of appropriate therapy 1
• Clinical follow-up at completion of therapy to ensure symptom resolution 1
• Post-treatment imaging studies are mandatory given the atypical organism 2
• Consider evaluation for immunocompromise or diabetes if no structural abnormality is found, as these increase risk for atypical UTI pathogens 1, 5