Abstract
Objective Outside of pregnancy, urinary pathogens such as Proteus and Klebsiella are considered more pathogenic than E. coli. During pregnancy, the implications of lower urinary tract infection (LUTI) with
more pathogenic bacteria are unclear. Thus, we sought to compare the risk of progression
from LUTI to pyelonephritis among women infected with these more pathogenic urinary
bacteria to those infected with E. coli.
Study Design Retrospective cohort of pregnant women with LUTI at single tertiary center from July
2013 to May 2019. Pathogenic infections (PI) were defined as asymptomatic bacteriuria
or acute cystitis urinary cultures positive for Proteus, Klebsiella, Enterobacter, Citrobacter, Acinetobacter, Staphylococcus, or Raoultella species. Demographic, infectious, antepartum, and postpartum data abstracted. Pregnant
women with PI compared with those with E. coli. Primary outcome was progression to pyelonephritis. Secondary outcomes included pyelonephritis
length of stay (LOS) >6 days, preterm birth (PTB), low birthweight (LBW), and measures
of pyelonephritis-related morbidity.
Results Of 686 pregnant women with LUTIs, 313 had urine culture growing out either PI or
E. coli, with 59 (12%) growing PI and 254 (54%) growing E. coli. Women with PI were more likely to be African American, have chronic hypertension,
and have history of preeclampsia. The primary species causing PI were Klebsiella (n = 29) and Proteus (n = 11). PI were not more likely to progress to pyelonephritis than E. coli LUTIs (10.9 vs. 14.5%; p = 0.67). Median LOS for pyelonephritis and other measures of pyelonephritis-related
morbidity did not differ nor did PTB or LBW rates. After controlling for race, body
mass index, history of preeclampsia, and history of pyelonephritis, PI were not associated
with increased odds of progression to pyelonephritis (adjusted odds ratio: 0.69, 95%
confidence interval: 0.27–1.80).
Conclusion Bacteria traditionally considered to be more pathogenic outside of pregnancy do not
progress to pyelonephritis at higher rates than E. coli in pregnancy, and are associated with similar pyelonephritis-related morbidity. Larger
studies are needed to confirm these findings.
Key Points
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Little is known about impact of uropathogen on progression to pyelonephritis and obstetric
outcomes.
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Rates of progression to pyelonephritis from UTI did not vary by uropathogen.
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Pyelonephritis-related morbidities and preterm birth rates were also similar among
uropathogens.
Keywords
pregnancy - pyelonephritis - anemia - sepsis - urinary tract infection - uropathogens
