Should I treat Staphylococcus (Staph) in a urine culture, especially in symptomatic patients or those with underlying medical conditions?

Treatment of Staphylococcus in Urine Culture

Treatment depends critically on whether the patient is symptomatic and the specific Staphylococcus species isolated—treat symptomatic infections and asymptomatic bacteriuria only in specific high-risk scenarios (pregnancy, pre-urologic procedures), but do not routinely treat asymptomatic Staph bacteriuria in most patients.

Key Decision Points

Distinguish Between Species and Clinical Context

• Staphylococcus saprophyticus is the second most common cause of acute UTI in young women (after E. coli) and typically causes symptomatic cystitis requiring treatment 1
• Staphylococcus aureus bacteriuria is less common (0.2-4% of positive cultures) and may represent contamination, colonization, true UTI, or bacteremic seeding from another site 2
• The IDSA guidelines strongly recommend against treating asymptomatic bacteriuria in most populations, including those with indwelling catheters, spinal cord injury, and non-pregnant patients 3

When to Treat: Symptomatic Patients

For symptomatic UTI with Staph species isolated:

• Treat all patients with dysuria, frequency, urgency, or systemic symptoms (fever, flank pain) when Staph is isolated in significant counts 4
• S. saprophyticus commonly presents with symptomatic cystitis in young women (mean age 32.7 years), particularly during spring and autumn months 5
• S. aureus bacteriuria with symptoms occurred in 33% of cases in one cohort, warranting treatment 6

Antibiotic selection for symptomatic S. saprophyticus:

• Trimethoprim-sulfamethoxazole is an excellent first-line option (94% susceptibility) 5
• Fluoroquinolones show 99% susceptibility 5
• Avoid relying on oral beta-lactams—45% of S. saprophyticus isolates are oxacillin-resistant 5

Antibiotic selection for symptomatic S. aureus:

• Trimethoprim-sulfamethoxazole shows 91% susceptibility and may be effective 4
• Consider vancomycin, teicoplanin, or linezolid for MRSA (24% of community isolates) 4
• Ciprofloxacin is FDA-approved for UTI caused by methicillin-susceptible S. epidermidis and S. saprophyticus 7

When to Treat: Asymptomatic Bacteriuria

Treat asymptomatic Staph bacteriuria ONLY in these scenarios:

• Pregnancy: This is the one exception where asymptomatic bacteriuria must always be treated due to 20-30 fold increased risk of pyelonephritis 3, 8
• Before urologic procedures breaching the mucosa: Single-dose antimicrobial prophylaxis is recommended 3
• Do NOT treat in patients with indwelling catheters, spinal cord injury, elderly patients, or those with functional impairment 3

Special Consideration: S. aureus Bacteriuria and Bacteremia Risk

S. aureus bacteriuria warrants heightened vigilance:

• 13% of patients with S. aureus bacteriuria had concurrent bacteremia at initial isolation 6
• 58% had persistent bacteriuria lasting median 4.3 months, and 16% developed subsequent staphylococcal infections (including 8 bacteremic episodes) up to 12 months later 6
• Blood cultures should be considered in higher-risk patients: those with urological instrumentation, diabetes, urinary catheterization, or systemic symptoms 2, 6

However, routine blood cultures are not supported for well, asymptomatic patients with S. aureus bacteriuria 2

Practical Algorithm

1. Identify the species: S. saprophyticus vs S. aureus
2. Assess symptoms: Dysuria, frequency, urgency, fever, flank pain?
   • If symptomatic: Treat with appropriate antibiotics based on susceptibilities
   • If asymptomatic: Proceed to step 3
3. Check for high-risk conditions:
   • Pregnant? → Treat
   • Upcoming urologic procedure? → Treat with single-dose prophylaxis
   • Otherwise healthy outpatient? → Do NOT treat 3
4. For S. aureus specifically: Consider blood cultures if patient has urological instrumentation, diabetes, catheterization, or any systemic signs 2, 6

Common Pitfalls to Avoid

• Do not treat asymptomatic bacteriuria in catheterized patients—this promotes antimicrobial resistance without clinical benefit 3
• Do not assume all coagulase-negative Staph is contamination—S. saprophyticus is a true pathogen in young women 1
• Do not ignore S. aureus bacteriuria in high-risk patients—it can be a harbinger of invasive infection, particularly in those with urological abnormalities or instrumentation 6
• Do not rely on beta-lactams for S. saprophyticus—nearly half are oxacillin-resistant 5
• Do not perform routine post-treatment cultures if symptoms resolve—focus on clinical response rather than laboratory confirmation 9