The Clinical Urine Culture: Enhanced Techniques Improve Detection of Clinically Relevant Microorganisms

Abstract

Enhanced Quantitative Urine Culture (EQUC) detects live microorganisms in the vast majority of urine specimens reported as “no growth” by the Standard Urine Culture protocol. Here, we evaluated an expanded set of EQUC conditions (Expanded Spectrum EQUC) to identify an optimal version that provides a more complete description of uropathogens in women experiencing urinary tract infection (UTI)-like symptoms. 150 adult urogynecology patient-participants were characterized using a self-completed validated UTI Symptoms Assessment (UTISA) questionnaire and asked: “Do you feel you have a UTI?” Women responding negatively were recruited in the No-UTI cohort, while women responding affirmatively were recruited into the UTI cohort; this latter cohort was reassessed with the UTISA questionnaire 3-7 days later. Baseline catheterized urine samples were plated using both Standard Urine Culture and Expanded Spectrum EQUC protocols: Standard Urine Culture inoculated 1uL onto 2 agars incubated aerobically; Expanded Spectrum EQUC inoculated three different volumes of urine onto 7 combinations of agars and environments. Compared to Expanded Spectrum EQUC, Standard Urine Culture missed 67% of uropathogens overall and 50% in participants with severe urinary symptoms. 36% of participants with missed uropathogens reported no symptom resolution after treatment by Standard Urine Culture results. Optimal detection of uropathogens could be achieved using the following: 100μL of urine plated onto Blood (BAP), Colistin Naladixic Acid (CNA), and MacConkey agars in 5% CO₂ for 48 hours. This Streamlined EQUC protocol achieved 84% uropathogen detection relative to 33% detection by Standard Urine Culture. The Streamlined EQUC protocol improves detection of uropathogens that are likely relevant for symptomatic women, giving clinicians the opportunity to receive additional information not currently reported using Standard Urine Culture techniques.