Routine prenatal care in the United States includes screening for asymptomatic bacteriuria (ASB), which occurs in 2 to 7 percent of pregnant women and can cause urinary tract infection and pyelonephritis. We present the case of a pregnant woman affected by multidrug resistant Klebsiella induced ASB during her prenatal screen, which was untreated due to a repeat urine culture showing mixed flora; subsequently, the patient's postpartum course was complicated by pyelonephritis and perinephric abscess, concluding in a radical nephrectomy. Current recommendations are to treat ASB after two consecutive voided urine cultures showing the same bacterial strain in quantitative counts of =/> 10(5) colony forming units (cfu)/mL or a single-catheterized specimen with quantitative count of =/> 10(2) cfu/mL. For women with ASB in their prenatal screen or other high risk factors, consideration should be given to testing urine cultures every trimester until the completion of pregnancy to prevent the complications of persistent bacteriuria.