Urinary microbiota of women with recurrent urinary tract infection: collection and culture methods

Abstract

Introduction and hypothesis: Many clinicians utilize standard culture of voided urine to guide treatment for women with recurrent urinary tract infections (RUTI). However, despite antibiotic treatment, symptoms may persist and events frequently recur. The cyclic nature and ineffective treatment of RUTI suggest that underlying uropathogens pass undetected because of the preferential growth of Escherichia coli. Expanded quantitative urine culture (EQUC) detects more clinically relevant microbes. The objective of this study was to assess how urine collection and culture methods influence microbial detection in RUTI patients.

Methods: This cross-sectional study enrolled symptomatic adult women with an established RUTI diagnosis. Participants contributed both midstream voided and catheterized urine specimens for culture via both standard urine culture (SUC) and EQUC. Presence and abundance of microbiota were compared between culture and collection methods.

Results: Forty-three symptomatic women participants (mean age 67 years) contributed specimens. Compared to SUC, EQUC detected more unique bacterial species and consistently detected more uropathogens from catheterized and voided urine specimens. For both collection methods, the most commonly detected uropathogens by EQUC were E. coli (catheterized: n = 8, voided: n = 12) and E. faecalis (catheterized: n = 7, voided: n = 17). Compared to catheterized urine samples assessed by EQUC, SUC often missed uropathogens, and culture of voided urines by either method yielded high false-positive rates.

Conclusions: In women with symptomatic RUTI, SUC and assessment of voided urines have clinically relevant limitations in uropathogen detection. These results suggest that, in this population, catheterized specimens analyzed via EQUC provide clinically relevant information for appropriate diagnosis.

Keywords: Enhanced urine culture; Recurrent urinary tract infection; Urinary microbiome; Urinary pathogen detection; Urine collection.

Figure 1.. Comparison of total microbiota detected by urine collection and culture method.

A) Rarefaction curve demonstrating the cumulative number of unique species detected (Y-axis) per participant (X-axis). Results are shown for catheterized (solid lines) and voided (dashed lines) urine samples cultured via SUC (black) and EQUC (gray). B) Cumulative microbiota profiles of all catheterized (N=43) and voided (N=42) urine samples cultured via SUC and EQUC. Total abundance (cumulative CFU/mL, Y-axis) of each genus detected is displayed for each urine collection and culture method.