The only study that looked at newborn outcomes found no difference in birth weights or premature births between the screened and unscreened cohorts.
No study examined this question in nonpregnant women or men.
What are the harms of such screening?
A single study of 372 pregnant women described potential prenatal and perinatal harms associated with screening and treatment. It found a slight increase in congenital abnormalities in the screened cohort (1.6%), compared with those who were not screened (1.1%). However, those who were not screened were presumably not prescribed antibiotics.
Does treatment of screening-detected asymptomatic bacteriuria improve health outcomes?
Twelve trials of pregnant women (2,377) addressed this issue. All but two were conducted in the 1960s and 1970s. Treatment varied widely; sulfonamides were the most common, including the now discarded sulfamethazine and sulfadimethoxine. Dosages and duration of treatment also were considerably higher and longer than current practice.
In all but one study, there were higher rates of pyelonephritis in the control group. A pooled risk analysis indicated that treatment reduced the risk of pyelonephritis by nearly 80% (relative risk, 0.24).
Seven studies found higher rates of low birth weight in infants born to mothers who were treated, but two studies reported a significant reduction in the risk of low birth weight.
Among the six trials that examined perinatal mortality, none found significant associations with treatment.
Five studies examined treatment in nonpregnant women with screening-detected asymptomatic bacteriuria, and one included men as well. Of the four that reported the rate of symptomatic infection or pyelonephritis, none found a significant difference between treatment and control groups. The single study that included men also found no significant difference between treatment and control groups.
Among the three studies that focused on older adults, there also were no significant between-group differences in outcomes.
What harms are associated with treatment of screening-detected asymptomatic bacteriuria?
Seven studies comprised pregnant women. Five reported congenital malformations in the intervention and control groups. Overall, there were very few cases of malformations, with more – although not significantly more – in the control groups.
Evidence related to other infant and maternal harms was “sparsely and inconsistently reported,” Dr. Henderson and coauthors noted, “and there was a lack of evidence on long-term neonatal outcomes after antibiotic treatment of asymptomatic bacteriuria in pregnancy.”
Two studies listed maternal adverse events associated with different treatments including vaginitis and diarrhea with ampicillin and rashes and nausea with nalidixic acid.
In terms of nonpregnant women and men, four studies reported adverse events. None occurred with nitrofurantoin or trimethoprim treatment; however, one study that included daily treatment with ofloxacin noted that 6% withdrew because of adverse events – vertigo and gastrointestinal symptoms.
Treatments didn’t affect hematocrit, bilirubin, serum urea, or nitrogen, although some studies found a slight reduction in serum creatinine.
Although there’s a need for additional research into this question, the new recommendations provide a good reason to further reduce unnecessary antibiotic exposure,, wrote in a second commentary.
These updated recommendations “contribute to the evolution of management of asymptomatic bacteriuria in healthy women,” wrote Dr. Nicolle of the University of Manitoba, Winnipeg. “However, questions remain about the risks and benefits of universal screening for and treatment of asymptomatic bacteriuria in pregnant women in the context of current clinical practice. The effects of changes in fetal-maternal care, of low- compared with high-risk pregnancies, and of health care access need to be understood. In the short term, application of current diagnostic recommendations for identification of persistent symptomatic bacteriuria with a second urine culture may provide an immediate opportunity to limit unnecessary antimicrobial use for some pregnant women.”
No conflicts of interest were reported by the USPSTF authors, nor by Dr. Leis, Dr. Soong, or Dr. Nicolle. The USPSTF report was funded by the Agency for Healthcare Research and Quality.
SOURCES: U.S. Preventive Services Task Force. ; Henderson JT et al. ; Leis JA and Soong C. JAMA. 2019. ; Nicolle LE.