CC BY-NC-ND 4.0 · AJP Rep 2024; 14(01): e80-e84
DOI: 10.1055/s-0044-1779031
Original Article

Urinary Tract Infection and Progression to Pyelonephritis: Group B Streptococcus versus E. coli

1   Department of Pediatrics, Johns Hopkins University, Baltimore, Maryland
2   Department of OBGYN, University of Utah, Salt Lake City, Utah
3   Department of Urology, University of Michigan, Ann Arbor, Michigan
Kristin E. Weaver
4   Department of Obstetrics and Gynecology, Duke University, Durham, North Carolina
R. Phillips Heine
5   Department of Obstetrics and Gynecology, Atrium Health Wake Forest, Winston-Salem, North Carolina
6   Department of Obstetrics and Gynecology, Yale University, New Haven, Connecticut
Sarah K. Dotters-Katz
4   Department of Obstetrics and Gynecology, Duke University, Durham, North Carolina
› Author Affiliations
Funding None.


Objective Group B Streptococcus (GBS) colonization of the lower urinary tract in pregnancy is associated with severe infections such as chorioamnionitis, endometritis, and pyelonephritis. The objective of this study was to compare rates of progression to pyelonephritis between GBS and Escherichia coli lower urinary tract infections (LUTIs), as well as compare infectious and obstetric morbidity secondary to these pathogens.

Study Design Retrospective cohort of pregnant women with LUTIs (asymptomatic bacteria or acute cystitis [AC]) from a single health system between July 2013 and May 2019. Demographic, infectious, antepartum, and intrapartum data were abstracted from medical records of women with GBS or E. coli LUTI. The primary outcome was progression to pyelonephritis. Secondary outcomes included pyelonephritis-related anemia, sepsis, pyelonephritis length of stay (LOS), median gestational age (GA) at delivery, preterm delivery, and low birth weight (LBW). Logistic regression was used to calculate the adjusted odds of the primary outcome.

Results Of 729 pregnant women with urinary colonization, 433 were culture positive for one of the aforementioned bacteria, with 189 (43.6%) having GBS and 244 (56.4%) having E. coli. Women with E. coli were more likely to be younger, use tobacco, have a history of AC, and have a history of preterm birth. Rates of progression to pyelonephritis were markedly higher with E. coli (15.6%) than with GBS (1.1%; p < 0.001). Median LOS for pyelonephritis and pyelonephritis-related morbidities did not differ. Median GA at delivery, preterm delivery, and LBW rates also did not differ. In adjusted analysis, controlling for history of AC, insurance status, tobacco use, prior preterm birth, primary infection type, and maternal age, women with GBS LUTI had markedly decreased odds of developing pyelonephritis in pregnancy compared with those with E. coli (adjusted odds ratio: 0.04, 95% confidence interval: 0.01–0.28).

ConclusionEscherichia coli infections progress to pyelonephritis in pregnancy at markedly higher rates than GBS, although obstetric outcomes are similar.


This work was presented as a poster presentation at the Society for Maternal-Fetal Medicine's 40th Annual Pregnancy meeting in February 2020 in Dallas, TX.

Supplementary Material

Publication History

Received: 14 June 2020

Accepted: 22 October 2023

Article published online:
18 February 2024

© 2024. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (

Thieme Medical Publishers, Inc.
333 Seventh Avenue, 18th Floor, New York, NY 10001, USA

  • References

  • 1 Abou Heidar NF, Degheili JA, Yacoubian AA, Khauli RB. Management of urinary tract infection in women: a practical approach for everyday practice. Urol Ann 2019; 11 (04) 339-346
  • 2 Foxman B. Epidemiology of urinary tract infections: incidence, morbidity, and economic costs. Am J Med 2002; 113 (Suppl 1A): 5S-13S
  • 3 Kalinderi K, Delkos D, Kalinderis M, Athanasiadis A, Kalogiannidis I. Urinary tract infection during pregnancy: current concepts on a common multifaceted problem. J Obstet Gynaecol 2018; 38 (04) 448-453
  • 4 Nicolle LE. Asymptomatic bacteriuria and bacterial interference. Microbiol Spectr 2015 ;3(05)
  • 5 Allen VM, Yudin MH. No. 276-management of group B streptococcal bacteriuria in pregnancy. J Obstet Gynaecol Can 2018; 40 (02) e181-e186
  • 6 Olsen IE, Groveman SA, Lawson ML, Clark RH, Zemel BS. New intrauterine growth curves based on United States data. Pediatrics 2010; 125 (02) e214-e224
  • 7 ACOG Practice Bulletin No. 95: anemia in pregnancy. Obstet Gynecol 2008; 112 (01) 201-207
  • 8 Hill JB, Sheffield JS, McIntire DD, Wendel Jr GD. Acute pyelonephritis in pregnancy. Obstet Gynecol 2005; 105 (01) 18-23
  • 9 Rosett HA, Krischak MK, Sachdeva S. et al. Lower urinary pathogens: do more pathogenic bacteria increase the risk of pyelonephritis?. Am J Perinatol 2022; 39 (05) 473-478
  • 10 Dotters-Katz SK, Heine RP, Grotegut CA. Medical and infectious complications associated with pyelonephritis among pregnant women at delivery. Infect Dis Obstet Gynecol 2013; 124102
  • 11 Muller AE, Oostvogel PM, Steegers EA, Dörr PJ. Morbidity related to maternal group B streptococcal infections. Acta Obstet Gynecol Scand 2006; 85 (09) 1027-1037