What antibiotic should be given to a patient with a urinary tract infection caused by Group D Streptococcus, with 10,000-25,000 colony forming units per mL in the urine culture?

Antibiotic Treatment for Group D Streptococcus (Non-Enterococcus) UTI

For this patient with Group D Streptococcus (not Enterococcus) urinary tract infection, treat with amoxicillin 500 mg orally every 8 hours for 7-14 days, as this organism is typically highly susceptible to penicillins and the colony count (10,000-25,000 CFU/mL) represents a true infection in a female patient.

Understanding the Organism

Group D Streptococcus (non-Enterococcus) includes organisms like Streptococcus bovis and Streptococcus equinus, which are distinct from enterococci and have different antibiotic susceptibility patterns. 1

• These organisms are typically highly susceptible to penicillin G (MIC ≤0.1 μg/mL) 1
• Unlike enterococci, they do not require combination therapy with aminoglycosides 1
• They respond well to standard beta-lactam antibiotics 1

Classification as Complicated vs. Uncomplicated UTI

Since this is a female patient, the UTI should be classified based on the presence of other complicating factors, not gender alone. 1, 2

• Male gender is a complicating factor, but female gender alone does not make a UTI complicated 1
• The colony count of 10,000-25,000 CFU/mL is significant in symptomatic patients 1
• Assess for other complicating factors: obstruction, foreign body, incomplete voiding, recent instrumentation, immunosuppression, or indwelling catheter 1

First-Line Treatment Recommendations

Oral amoxicillin is the preferred first-line agent for Group D Streptococcus UTI:

• Amoxicillin 500 mg orally every 8 hours is specifically recommended for uncomplicated urinary tract infections due to susceptible streptococci 1
• Alternative: Ampicillin 200-300 mg/kg/day IV divided every 4-6 hours (up to 12 g daily) if parenteral therapy is needed 1
• Duration: 7-14 days depending on clinical response and presence of complicating factors 1

Alternative Oral Options

If the patient has a penicillin allergy or intolerance:

• Cephalexin 500 mg orally every 6 hours for 7-14 days (first-generation cephalosporin with excellent activity against Group D Streptococcus) 1
• Cefuroxime 500 mg orally every 12 hours for 7-14 days (second-generation cephalosporin) 1
• Avoid fluoroquinolones as first-line therapy due to antimicrobial stewardship concerns and unnecessary broad-spectrum coverage 3, 4

Parenteral Options (If Needed)

For patients requiring hospitalization or unable to tolerate oral therapy:

• Penicillin G 200,000-300,000 U/kg/day IV divided every 4 hours (up to 12-24 million U daily) 1
• Ceftriaxone 1-2 g IV once daily is a convenient alternative for outpatient parenteral therapy 1
• Ampicillin 1-2 g IV every 6 hours is equally effective 1

When NOT to Use Certain Antibiotics

Avoid the following for this specific organism:

• Do NOT add gentamicin or other aminoglycosides - combination therapy is not needed for Group D Streptococcus (unlike enterococci) 1
• Vancomycin should only be used if the patient has a severe beta-lactam allergy, as it is less effective than penicillins for this organism 1
• Linezolid is not indicated - this is reserved for vancomycin-resistant enterococci, not Group D Streptococcus 1, 5

Treatment Duration Considerations

Duration should be based on clinical factors:

• 7 days minimum for uncomplicated UTI in females without complicating factors 1
• 10-14 days if any complicating factors are present (diabetes, immunosuppression, recurrent UTI, incomplete voiding) 1
• Shorter courses (5 days) are NOT appropriate for Group D Streptococcus UTI, as these organisms may require longer treatment than typical E. coli cystitis 1

Important Clinical Pitfalls

Common mistakes to avoid:

• Do not dismiss the low colony count (10,000-25,000 CFU/mL) - this is significant in symptomatic patients and with proper collection technique 1
• Do not confuse Group D Streptococcus with Enterococcus - the culture specifically states "not Enterococcus," so combination therapy is unnecessary 1
• Do not use empiric broad-spectrum antibiotics (carbapenems, ceftazidime-avibactam) for this highly susceptible organism 1
• Consider gastrointestinal evaluation - Group D Streptococcus (especially S. bovis) bacteremia has been associated with colonic pathology, though this association is less clear for UTI 1

Monitoring and Follow-Up

Clinical response should be assessed:

• Symptoms should improve within 48-72 hours of appropriate therapy 1
• If no improvement, consider repeat urine culture to assess for resistance or alternative diagnosis 1
• Follow-up urine culture is not routinely needed if symptoms resolve completely 1