What is the recommended treatment for a pregnant patient with 10,000-25,000 colony-forming units (CFU) of Staphylococcus saprophyticus in urine?

Treatment of Staphylococcus saprophyticus Bacteriuria in Pregnancy

Pregnant women with Staphylococcus saprophyticus bacteriuria should be treated with a 4-7 day course of nitrofurantoin 100 mg twice daily or an appropriate beta-lactam antibiotic, regardless of symptom status. 1

Background and Rationale

Asymptomatic bacteriuria (ASB) in pregnancy occurs in 2-7% of pregnant women and requires treatment to prevent adverse outcomes. The 2019 Infectious Diseases Society of America (IDSA) guidelines strongly recommend screening for and treating ASB in pregnancy due to the risk of progression to pyelonephritis, preterm labor, and low birth weight. 1

While the colony count of 10,000-25,000 CFU/mL may be considered low for some urinary pathogens, S. saprophyticus is known to cause urinary tract infections even at lower colony counts than the traditional threshold of 100,000 CFU/mL. 2 Therefore, this finding should be considered clinically significant in a pregnant patient.

Treatment Algorithm

1. Confirm the diagnosis:

   • S. saprophyticus is a common uropathogen, particularly in young women
   • Colony counts of 10,000-25,000 CFU/mL are significant for this organism 2

2. First-line treatment options:

   • Nitrofurantoin 100 mg orally twice daily for 4-7 days 1, 3
   • Ampicillin 500 mg orally four times daily for 4-7 days 4
   • Cephalexin 500 mg orally four times daily for 4-7 days 4

3. Duration of therapy:

   • A 4-7 day course is recommended over shorter durations 1
   • A randomized controlled trial demonstrated that a 7-day regimen of nitrofurantoin was significantly more effective than a 1-day regimen (86.2% vs 75.7% cure rate) 3

4. Follow-up:

   • Obtain a test-of-cure urine culture 1-2 weeks after completing treatment
   • No recommendation exists for or against repeat screening during pregnancy following treatment 1

Antimicrobial Susceptibility Considerations

S. saprophyticus is typically susceptible to:

• Ampicillin
• Cephalexin
• Nitrofurantoin
• Trimethoprim-sulfamethoxazole (avoid in late pregnancy)

It is characteristically resistant to nalidixic acid and novobiocin. 4

Important Clinical Considerations

• Do not use single-dose therapy: Evidence shows that single-dose treatment is significantly less effective than standard 7-day regimens for ASB in pregnancy 3

• Avoid prophylactic antibiotics: After successful treatment, antimicrobial agents should not be used for prophylaxis during pregnancy 1

• Treatment is necessary even without symptoms: The 2019 IDSA guidelines strongly recommend treating ASB in pregnancy regardless of symptom status, as it reduces the risk of pyelonephritis from 20-35% to 1-4% 1

• Preferred agents in pregnancy: Nitrofurantoin and β-lactam antibiotics (ampicillin or cephalexin) are preferred due to their established safety profile in pregnancy 1

By following these evidence-based recommendations, you can effectively treat S. saprophyticus bacteriuria in pregnancy and reduce the risk of complications such as pyelonephritis, preterm birth, and low birth weight.