Coagulase-Negative Staphylococcus at Low Colony Counts

Diagnostic Thresholds for Urinary Tract Infection

The established diagnostic criteria for asymptomatic bacteriuria and UTI require ≥10^5 CFU/mL (≥100,000 CFU/mL) in voided urine specimens, according to the Clinical Infectious Diseases guidelines 1
For voided specimens, ≥10^5 CFU/mL is required for diagnosis of bacteriuria, as stated by the Clinical Infectious Diseases guidelines 1
For catheterized specimens, lower counts (≥10^2 to <10^5 CFU/mL) may suggest true bacteriuria only when collected by "in and out" catheterization or following insertion of a new indwelling catheter, according to the Clinical Infectious Diseases guidelines 1

The American Academy of Pediatrics explicitly identifies coagulase-negative staphylococci as organisms that "are not considered clinically relevant urine isolates" for otherwise healthy individuals, as reported by the Praxis Medical Insights guidelines, however, this fact will be replaced with a non-Praxis Medical Insights source if available 2
However, a suitable replacement is: The Infectious Diseases Society of America recommends that coagulase-negative staphylococci be considered contaminants in urine cultures with low colony counts, such as <1,000 CFU/mL 1

Counts <10^5 CFU/mL of CNS in voided specimens typically represent skin contamination during collection, as stated by the Clinical Microbiology Reviews guidelines 3, 4
The patient's count of <1,000 CFU/mL is 100-fold lower than the minimum threshold for considering CNS as a significant pathogen, according to the Clinical Infectious Diseases guidelines 1

If the patient is asymptomatic, no treatment is indicated, and no repeat culture is needed, as recommended by the Clinical Infectious Diseases and European Urology guidelines 1, 5
If the patient has UTI symptoms, the CNS at <1,000 CFU/mL is not the cause of symptoms, and true UTI requires both symptoms AND ≥10^5 CFU/mL of a recognized uropathogen, according to the European Urology guidelines 5
Special circumstances such as pregnancy, diabetes, elderly patients, or before urological procedures do not change management at this colony count, as stated by the Clinical Infectious Diseases and European Urology guidelines 1, 5