What is the treatment for a urine culture showing >100,000 Colony-Forming Units (CFU) of Staphylococcus coagulase-negative in an elderly male?

Treatment for Coagulase-Negative Staphylococcus in Elderly Male Urine Culture

In elderly males with >100,000 CFU of coagulase-negative staphylococcus in urine culture but without urinary symptoms, antimicrobial treatment is strongly recommended against as this represents asymptomatic bacteriuria (ASB), not a urinary tract infection requiring treatment. 1

Diagnostic Assessment

Before considering treatment, determine if this represents true infection or asymptomatic bacteriuria:

• Symptomatic UTI signs to assess for:

  • Presence of specific urinary symptoms: dysuria, frequency, urgency, incontinence
  • Systemic symptoms: fever, rigors, altered mental status
  • Costovertebral angle tenderness 2

• Important distinction:

  • Asymptomatic bacteriuria (ASB): bacteria in urine without symptoms
  • True UTI: bacteria in urine WITH symptoms

Treatment Algorithm

1. If NO urinary symptoms or systemic signs of infection:

   • Do NOT treat with antibiotics
   • Coagulase-negative staphylococcus in urine without symptoms represents ASB
   • The Infectious Diseases Society of America strongly recommends against treating ASB in elderly patients 1

2. If clear UTI symptoms are present:

   • Obtain urine and blood cultures before starting antibiotics
   • Consider empiric treatment with:
     • Cefpodoxime 200mg twice daily (adjust for renal function)
     • OR Amoxicillin-clavulanate 875mg twice daily 2

3. If sepsis is suspected (fever, altered mental status, hypotension):

   • Start broad-spectrum antibiotics within 1 hour
   • Initiate fluid resuscitation (30ml/kg within 3 hours)
   • Monitor closely for response 2

Rationale for Non-Treatment of ASB

The recommendation against treating ASB in elderly males is based on:

1. Harm outweighs benefit:

   • High certainty for harm from antibiotics
   • Low certainty of any benefit from treatment 1

2. Specific harms of treatment:

   • Increased risk of antibiotic-associated diarrhea including C. difficile infection
   • Promotion of antimicrobial resistance
   • Adverse drug reactions 1

3. Lack of evidence for benefit:

   • No improvement in mental status, falls, or other outcomes
   • No reduction in risk of sepsis, death, or hospitalizations 1

Special Considerations

• Delirium without other symptoms: Current evidence does not suggest a causal relationship between bacteriuria and changes in mental status or falls in the elderly 1

• Indwelling catheters: Coagulase-negative staphylococci are often associated with catheter-related infections. If the patient has an indwelling catheter, consider catheter removal or replacement before deciding on antibiotic therapy 3

• Antibiotic selection if treatment is warranted: Coagulase-negative staphylococci have become increasingly resistant to multiple antibiotics. If treatment is necessary due to symptomatic infection, antibiotic selection should be guided by susceptibility testing 4, 5

Common Pitfalls to Avoid

1. Overtreatment: The most common error is treating ASB as if it were a UTI, leading to unnecessary antibiotic use and associated harms

2. Misattribution of symptoms: Avoid attributing non-specific symptoms like altered mental status or falls to bacteriuria without other UTI symptoms 1

3. Failure to distinguish colonization from infection: Coagulase-negative staphylococci are often skin contaminants or colonizers rather than true pathogens, especially in catheterized patients 4

4. Ignoring antibiotic resistance: If treatment is necessary, be aware that coagulase-negative staphylococci often show resistance to multiple antibiotics, with Staphylococcus haemolyticus having particularly high resistance rates 5

Remember that distinguishing between ASB and UTI in older adults can be challenging, but implementing a systematic approach to diagnosis using standard criteria is essential to avoid inappropriate antibiotic use 6.