A 43-year-old primigravid woman at 10 weeks' gestation comes to the physician for a prenatal visit

A 43-year-old primigravid woman at 10 weeks’ gestation comes to the physician for a prenatal visit. She is feeling well except for some occasional nausea. She has had no bleeding from the vagina, abdominal pain, dysuria, frequency, or urgency. She has asthma for which she occasionally uses an inhaler. Examination is normal for a woman at 10 weeks gestation. Urine dipstick is positive for nitrites and leukocyte esterase and a urine culture shows 50,000 colony forming units per milliliter of Escherichia coli. Which of the following is the most appropriate next step in management?

A. Wait to see if symptoms develop
B. Resend another urine culture
C. Obtain a renal ultrasound
D. Treat with oral antibiotics
E. Admit for intravenous antibiotics

Explanation: The correct answer is D. Asymptomatic bacteriuria is present in 2 to 9% of pregnant women. An association between asymptomatic bacteriuria and preterm delivery/low birth weight has been demonstrated. Therefore, all pregnant women should be screened for asymptomatic bacteriuria early in the pregnancy, and women who demonstrate bacteriuria (defined as a clean-catch, midstream urine specimen with 25,000 to 100,000 colony forming units per milliliter of a single organism) should be treated. E. Coli is the organism that is isolated in roughly 80% of cases while other gram-negative organisms (e.g., Klebsiella, Enterobacter, and Proteus species) and gram-positive cocci (e.g. enterococci and group B streptococci) are responsible for the remainder. Antibiotic sensitivities are often available at the time of diagnosis of the asymptomatic bacteriuria, which will allow for correct choice of medications. A 3-day course of antibiotics may be given. Possible choices include trimethoprim-sulfamethoxazole, nitrofurantoin, and cephalexin. Ampicillin and amoxicillin can also be used, but up to 1/3 of E. Coli isolates will be resistant to these drugs. Therefore, these drugs should be chosen only if the organism is sensitive. 10 days after completing the medication, the patient should have a follow-up urine culture as a test-of-cure. Waiting to see if symptoms develop (choice A) is not appropriate. Bacteriuria, even without symptoms, has been shown to be associated with preterm labor and low birth weight. Asymptomatic bacteriuria should, therefore, be treated. Resending another urine culture (choice B) would not be the most appropriate next step. This patient already has demonstrable bacteriuria and treatment should be instituted. Admitting for intravenous antibiotics (choice E) or obtaining a renal ultrasound (choice C) would not be necessary. This patient has asymptomatic bacteriuria and not pyelonephritis; therefore, a 3-day course of oral antibiotics followed by a repeat culture 10 days later is all that is necessary.