Coagulase-Negative Staphylococcus at <1,000 CFU/mL: Clinical Significance
A coagulase-negative staphylococcus (CNS) urine colony count of less than 1,000 CFU/mL is not a cause for concern and should not be treated, as this falls far below the diagnostic threshold for urinary tract infection and most likely represents contamination or benign colonization. 1, 2
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. 1 Your colony count of <1,000 CFU/mL is two orders of magnitude below this threshold, making it clinically insignificant in the vast majority of cases.
Key diagnostic principles:
- For voided specimens: ≥10^5 CFU/mL is required for diagnosis of bacteriuria 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 1
- Your count of <1,000 CFU/mL: Does not meet criteria for significant bacteriuria by any collection method 1
Clinical Significance of Coagulase-Negative Staphylococci
The American Academy of Pediatrics explicitly identifies coagulase-negative staphylococci as organisms that "are not considered clinically relevant urine isolates" for otherwise healthy individuals. 2 This designation applies even when colony counts are higher than yours.
When CNS may be pathogenic (none apply to your scenario):
- Complicated UTI with indwelling catheters: CNS can cause infection in patients with chronic catheterization, but typically at counts ≥10^5 CFU/mL 3, 4
- Acute cystitis in young women: Staphylococcus saprophyticus specifically can cause symptomatic cystitis, but requires colony counts ≥10^5 CFU/mL and presence of symptoms 5, 4
- Nosocomial infections: CNS are important pathogens in immunocompromised patients with foreign bodies, but again require higher colony counts 6
Why Your Result is Not Concerning
Colony count interpretation:
- Counts <10^5 CFU/mL of CNS in voided specimens typically represent skin contamination during collection 1
- Even in complicated UTI, CNS requires counts ≥10^5 CFU/mL to be considered significant 3
- Your count of <1,000 CFU/mL is 100-fold lower than the minimum threshold 1
Common pitfall to avoid: Do not treat asymptomatic bacteriuria or low colony counts, as this may be harmful by selecting for antimicrobial resistance and potentially eradicating protective commensal flora. 1, 2
Clinical Management Algorithm
If the patient is asymptomatic:
If the patient has UTI symptoms (dysuria, urgency, frequency):
- The CNS at <1,000 CFU/mL is not the cause of symptoms 2
- Look for alternative diagnoses or consider repeat culture if symptoms persist 7
- True UTI requires both symptoms AND ≥10^5 CFU/mL of a recognized uropathogen 2, 7
Special circumstances that do NOT change management at this colony count: