(719) Serial urine cultures to assess for Group B Strep in pregnancy

To determine if Group B Streptococcus (GBS) presence in the urine fluctuates on a weekly basis in the third trimester of pregnancy.

Study Design: This was a longitudinal, observational, cohort study. Pregnant patients who required weekly visits from 32 weeks gestation onward were recruited. Weekly urine samples were obtained using Peezy midstream urine collection devices, designed to minimize post-urethral contamination. The research lab cultured each urine sample using the standard or expanded quantitative urine culture techniques (SUC or EQUC). The clinical microbiology lab analyzed rectovaginal swabs obtained by routine clinical practice.

Results: Table 1 shows the characteristics of the 24 patients who provided ³1 urine sample during the timeframe. Cohort patients had mean age of 30.5 and mean BMI of 39.7; 62.5% had gestational or pre-gestational diabetes. One GBS-negative patient had a spontaneous preterm delivery. Figure 1 shows the longitudinal culture results. Four patients had GBS detected in ³1 by SUC. One (patient #U) had GBS detected by EQUC. One patient (patient #J) grew GBS by SUC every week, except week 36, typically the timepoint for routine rectovaginal GBS swab. That patient did not have a clinical GBS swab performed, as GBS bacteriuria had been detected in the first trimester. Four patients with positive GBS by clinical rectovaginal swab did not have GBS colonies present in any research urine cultures.

Conclusion: Our data suggest that urinary GBS presence may fluctuate on a week-to-week basis. This could indicate that screening at a single time point does not fully capture all patients with GBS colonization. The current Obstetrics practice assumes that urine is sterile at baseline and that GBS bacteriuria at any point indicates colonization. Yet, recent data in the Urology and Urogynecology fields have revealed evidence of a resident urinary microbiome in asymptomatic individuals. This points to the importance of characterizing the urinary microbiome in pregnancy and the temporal pattern of urinary GBS presence.