Urinary microbes and postoperative urinary tract infection risk in urogynecologic surgical patients

Women have a 20% risk of developing a urinary tract infection (UTI) following urogynecologic surgery. This study assessed the association of postoperative UTI with bacteria in preoperative samples of catheterized urine.

Immediately before surgery, vaginal swabs, perineal swabs, and catheterized urine samples were collected, and the V4 region of the 16S ribosomal RNA (rRNA) gene was sequenced. The cohort was dichotomized in two ways: (1) standard day-of-surgery urine culture result (positive/negative), and (2) occurrence of postoperative UTI (positive/negative). Characteristics of bladder, vaginal, and perineal microbiomes were assessed to identify factors associated with postoperative UTI.

Eighty-seven percent of the 104 surgical patients with pelvic organ prolapse/urinary incontinence (POP/UI) were white; mean age was 57 years. The most common genus was Lactobacillus, with a mean relative abundance of 39.91% in catheterized urine, 53.88% in vaginal swabs, and 30.28% in perineal swabs. Two distinct clusters, based on dispersion of catheterized urine (i.e., bladder) microbiomes, had highly significant (p < 2.2-16) differences in age, microbes, and postoperative UTI risk. Postoperative UTI was most frequently associated with the bladder microbiome; microbes in adjacent pelvic floor niches also contributed to UTI risk. UTI risk was associated with depletion of Lactobacillus iners and enrichment of a diverse mixture of uropathogens.

Postoperative UTI risk appears to be associated with preoperative bladder microbiome composition, where an abundance of L. iners appears to protect against postoperative UTI.