Evidence of Uncultivated Bacteria in the Adult Female Bladder

TLDR

Urine is traditionally regarded as sterile when standard cultures fail to grow pathogens. The study aimed to determine whether adult female bladders harbor bacteria undetectable by routine culture and to recommend optimal urine collection methods. Participants without urinary tract infection provided voided, transurethral, and suprapubic urine samples, which were examined by culture, microscopy, and 16S rRNA sequencing. Uncultivated bacteria were frequently detected in all sample types, with similar communities across collection methods, indicating that some women’s bladders contain such bacteria, though their viability and clinical relevance remain uncertain.

Abstract

ABSTRACT Clinical urine specimens are usually considered to be sterile when they do not yield uropathogens using standard clinical cultivation procedures. Our aim was to test if the adult female bladder might contain bacteria that are not identified by these routine procedures. An additional aim was to identify and recommend the appropriate urine collection method for the study of bacterial communities in the female bladder. Consenting participants who were free of known urinary tract infection provided urine samples by voided, transurethral, and/or suprapubic collection methods. The presence of bacteria in these samples was assessed by bacterial culture, light microscopy, and 16S rRNA gene sequencing. Bacteria that are not or cannot be routinely cultivated (hereinafter called uncultivated bacteria) were common in voided urine, urine collected by transurethral catheter (TUC), and urine collected by suprapubic aspirate (SPA), regardless of whether the subjects had urinary symptoms. Voided urine samples contained mixtures of urinary and genital tract bacteria. Communities identified in parallel urine samples collected by TUC and SPA were similar. Uncultivated bacteria are clearly present in the bladders of some women. It remains unclear if these bacteria are viable and/or if their presence is relevant to idiopathic urinary tract conditions.