A hospital’s surveillance validation process uncovered a hidden threat to antimicrobial stewardship: contaminated urine cultures leading to unnecessary antibiotic prescriptions. This prompted a collaborative effort to improve specimen integrity and reduce inappropriate antimicrobial use through targeted diagnostic stewardship.
Infection preventionists are well-versed in monitoring blood culture contamination rates, but should urine cultures receive the same scrutiny? That was the unexpected question facing one facility in early 2024, after implementing a new electronic medical record (EMR) system and infection prevention surveillance platform.
During routine surveillance validation, the infection prevention (IP) team noted a troubling trend: a high volume of contaminated urine cultures originating from the emergency department (ED). This discovery launched a deeper investigation into 2 critical questions: Should urine culture contamination be monitored more formally? And could improving diagnostic accuracy support antimicrobial stewardship efforts?
Between January and June 2024, the IP team collaborated with pharmacy and ED clinicians to conduct a retrospective chart review of 238 contaminated urine culture cases. They assessed the presence of National Healthcare Safety Network (NHSN)-recognized urinary tract infection (UTI) symptoms and whether antimicrobials were prescribed despite specimen contamination.
The findings were eye-opening. Sixty-seven percent of patients with contaminated urine specimens were treated with antibiotics, even though no alternative infection source was documented. Of particular concern, 59% of patients without any NHSN-defined UTI symptoms were prescribed antibiotics—amounting to at least 61 patients over 6 months potentially receiving unnecessary antimicrobial therapy based on invalid test results. The duration of therapy ranged from 1 to 14 days.
These results highlighted an underrecognized intersection between diagnostic and antimicrobial stewardship. In response, the team plans to establish routine monitoring of urine culture contamination rates, improve collection protocols in the ED, and launch educational campaigns emphasizing proper testing indications and interpretation.
By addressing the root cause, specimen integrity, this initiative aims to curb antibiotic overuse and enhance diagnostic precision. The case underscores how infection preventionists can expand their scope to include diagnostic stewardship, creating new opportunities for collaboration and improved patient safety across care settings.
The information was presented as a poster at the Association of Professionals in Infection Control and Epidemiology Conference and Expo, held in Phoenix, Arizona, from June 16 to 18, 2025, by Andrea Lynn Cromer, MPH, RN, CIC, CPH, from Truvian Healthcare System, San Diego, California.
Coauthors were Amy Carroll, BSN, RN, CIC; Lee Connor, MD; Deborah Langshaw, PharmD; Melissa Morgan, PharmD; and Ruben Garz, MLS(ASCP), all of whom are from Hamilton Medical Center, Dalton, Georgia.
