What is the recommended treatment for a pregnant woman in her second trimester with a urine culture positive for Acinetobacter baumannii (50,000-99,000 Colony-Forming Units per Milliliter (CFU/mL))?

Treatment of Acinetobacter baumannii Urinary Tract Infection in Pregnancy

For a pregnant woman in her second trimester with a urine culture showing Acinetobacter baumannii (50,000-99,000 CFU/mL), ampicillin-sulbactam is the recommended first-line treatment due to its intrinsic activity against A. baumannii and better safety profile compared to other options.

Treatment Selection Algorithm

First-line therapy:

• For isolates susceptible to sulbactam (MIC ≤4 mg/L), use ampicillin-sulbactam as the preferred treatment due to its better safety profile compared to polymyxins 1, 2
• Administer ampicillin-sulbactam as a 4-hour infusion of 3g sulbactam every 8 hours (9-12g/day total) for optimal efficacy 1, 2

Alternative options (if sulbactam resistance):

• For carbapenem-susceptible isolates in areas with low resistance rates, carbapenems (imipenem, meropenem, doripenem) can be used 3, 4
• For isolates resistant to both sulbactam and carbapenems, colistin may be necessary, though it carries higher risk of nephrotoxicity 2

Rationale for Treatment Selection

• Sulbactam has intrinsic activity against A. baumannii and can be effective at MIC ≤4 mg/L 3
• Clinical studies comparing sulbactam and colistin have shown comparable clinical and microbiological response rates 2
• Nephrotoxicity rates are significantly higher with colistin (33%) compared to sulbactam (15.3%), making sulbactam safer, especially during pregnancy 2
• High-dose sulbactam therapy (9-12 g/day divided into 3 daily doses) is recommended for severe infections 3, 2

Important Considerations During Pregnancy

• Ampicillin-sulbactam has established safety in pregnancy, making it preferable to newer agents with limited pregnancy data 5
• The FDA-approved indication for ampicillin-sulbactam includes treatment of infections due to susceptible strains of Acinetobacter 5
• Avoid unnecessary antibiotics, as Acinetobacter infections are often opportunistic in nature 6

Treatment Duration

• For uncomplicated UTIs, treatment can generally be completed in 7 days 1
• For complicated UTIs or those with systemic symptoms, extend treatment to 14 days 1
• Monitor clinical response and resolution of symptoms to guide treatment duration 1

Monitoring Recommendations

• Obtain follow-up urine cultures after completion of therapy to confirm eradication 2
• Monitor renal function during treatment, especially if colistin becomes necessary 2
• Assess for clinical improvement within 48-72 hours of initiating therapy 1

Common Pitfalls to Avoid

• Underdosing sulbactam may lead to treatment failure; ensure adequate dosing of 9-12g/day for severe infections 2
• Not considering local resistance patterns when selecting therapy 3, 4
• Using ertapenem, which lacks activity against A. baumannii, unlike other carbapenems 4
• Failing to remove or replace urinary catheters when present, as they are risk factors for developing A. baumannii infections 1

Combination Therapy Considerations

• There are insufficient data to recommend combination therapy over monotherapy for directed treatment of A. baumannii infections 3
• For clinical failures or infections with isolates having MICs at the upper limit of susceptibility, combination therapy may be considered 2
• The routine combination of colistin plus rifampin is not recommended due to lack of proven benefit 3