Explanation for false-positive urine cultures obtained by bag technique

Area of Science:

• Pediatrics
• Microbiology
• Clinical Diagnostics

Background:

• Accurate urine culture is crucial for diagnosing urinary tract infections in neonates.
• Previous studies suggested the urine bag technique was reliable for circumcised male infants over one month old.
• The reliability of this method in newborns, including females and uncircumcised males, remained unverified.

Purpose of the Study:

• To evaluate the accuracy of the urine bag technique for obtaining sterile urine cultures in healthy newborns.
• To determine if the urine bag method yields false-positive results in neonates of different sexes and circumcision statuses.

Main Methods:

• A prospective study was conducted on 98 healthy newborns in a hospital nursery.
• Periurethral and urine specimens were collected sequentially.
• Urine was collected using a urine bag after periurethral cleansing, and both specimens were cultured.

Main Results:

• Pathogens isolated from bag urine cultures frequently reflected periurethral flora (95% concordance).
• The urine bag technique resulted in false-positive cultures in 16 of 21 cases (76%).
• Periurethral contamination was significantly more common in female neonates compared to males (P = .004).

Conclusions:

• The urine bag technique is not reliable for obtaining sterile urine cultures in newborns due to periurethral contamination.
• Catheterization or suprapubic aspiration are preferred methods for urine specimen collection in female and uncircumcised male neonates.
• Further development of contamination-free urine bag collection methods is needed.