Management of Staphylococcus epidermidis in Urine Culture
In most clinical scenarios, S. epidermidis isolated from urine should NOT be treated, as it typically represents either contamination or asymptomatic bacteriuria, both of which do not warrant antimicrobial therapy. 1
Key Clinical Decision Points
When NOT to Treat (Most Common Scenario)
Do not treat asymptomatic bacteriuria with S. epidermidis. The 2019 IDSA guideline explicitly recommends against treating asymptomatic bacteriuria in most populations, as treatment promotes antimicrobial resistance without clinical benefit. 1
Do not treat single positive cultures when contamination is likely. The Hospital Infection Control Practices Advisory Committee specifically discourages vancomycin treatment "in response to a single blood culture positive for coagulase-negative staphylococcus, if other blood cultures taken during the same time frame are negative (i.e., if contamination of the blood culture is likely)." 1 This principle extends to urine cultures, where S. epidermidis is a common skin contaminant. 2, 3
Avoid overtreatment based on laboratory findings alone. A 2017 meta-analysis found that 45% of asymptomatic bacteriuria cases are inappropriately treated, with female sex, pyuria, positive nitrites, and gram-negative organisms (though S. epidermidis is gram-positive) increasing odds of unnecessary treatment. 4
Exceptions: When Treatment IS Indicated
Treat S. epidermidis urinary tract infections ONLY when:
Patient has clear urinary symptoms (dysuria, frequency, urgency, suprapubic pain, fever with flank pain suggesting pyelonephritis) AND positive culture. 1
Structural urinary abnormalities are present, particularly:
Patient is undergoing endoscopic urologic procedures with anticipated mucosal trauma. 1
Patient is pregnant (one of the few populations where asymptomatic bacteriuria requires treatment). 1
Treatment Approach When Indicated
Antibiotic Selection
Check methicillin susceptibility first. Approximately 40% of S. epidermidis isolates demonstrate methicillin resistance, and cross-resistance with cephalosporins occurs. 2, 3
For methicillin-susceptible strains: Use penicillinase-resistant penicillins or first-generation cephalosporins. 3
For methicillin-resistant strains: Vancomycin is the drug of choice. 2, 3 For serious infections (e.g., pyelonephritis with bacteremia), consider vancomycin combined with rifampin or gentamicin. 3
Ciprofloxacin is FDA-approved for UTIs caused by methicillin-susceptible S. epidermidis, though susceptibility testing should guide therapy. 7
Special Considerations for Device-Related Infections
Device removal is often necessary. S. epidermidis produces extracellular slime forming biofilms on indwelling devices, requiring 100-1000 times higher antibiotic concentrations to eradicate compared to planktonic bacteria. 8
Antibiotics alone frequently fail when the organism is protected within biofilm on catheters or other devices. 8, 3
Common Pitfalls to Avoid
Do not reflexively treat positive urine cultures without symptoms. This is the most common error and drives antimicrobial resistance. 1, 4
Do not assume contamination in immunocompromised patients. S. epidermidis has emerged as a significant pathogen in granulocytopenic patients (particularly those with <100 cells/μL), where it warrants appropriate therapy. 2
Do not use vancomycin for routine prophylaxis of catheter-associated infections or for treating presumed infections when cultures are negative. 1
In pediatric populations, recognize that while S. epidermidis can cause true UTIs in children with anatomic abnormalities, it should not be treated as a first-line pathogen without clear clinical indication. 1, 6
Ensure proper specimen collection technique to minimize contamination, as S. epidermidis is normal skin flora. 1