Management of Asymptomatic MRSA Bacteriuria
Asymptomatic bacteriuria with MRSA at >100,000 CFU/mL should not be treated with antibiotics. 1
Definition and Diagnosis
- Asymptomatic bacteriuria (ASB) is defined as the presence of bacteria in the urine without symptoms of urinary tract infection 1
- For women, ASB is diagnosed when two consecutive urine specimens show ≥10^5 CFU/mL of the same bacterial strain 1, 2
- For men, a single clean-catch voided specimen with ≥10^5 CFU/mL is sufficient for diagnosis 1, 2
- The presence of pyuria with asymptomatic bacteriuria is not an indication for antimicrobial treatment 1
Evidence Against Treatment of Asymptomatic MRSA Bacteriuria
- The European Association of Urology (2024) strongly recommends against screening for or treating asymptomatic bacteriuria in patients without risk factors, including those with recurrent UTIs 1
- The Infectious Diseases Society of America (IDSA) guidelines clearly state that treatment of asymptomatic bacteriuria may be harmful 1
- A systematic review found that inappropriate treatment of asymptomatic bacteriuria occurs in approximately 45% of cases, contributing to antimicrobial resistance 3
- Studies show that isolation of gram-negative pathogens, pyuria, nitrite positivity, and female sex incorrectly increase the likelihood of receiving unnecessary treatment 3
Special Populations Where Treatment Is Indicated
- Pregnant women with asymptomatic bacteriuria should be treated to prevent complications 1, 2
- Patients undergoing urological procedures with expected mucosal bleeding should be screened and treated for asymptomatic bacteriuria 1
- Antimicrobial treatment may be considered for asymptomatic women with catheter-acquired bacteriuria that persists 48 hours after catheter removal 1
Specific Considerations for MRSA Bacteriuria
- MRSA bacteriuria is more common in patients with urological abnormalities, long-term care, male sex, older age, and comorbidities 4
- In a study of MRSA bacteriuria, only 1 out of 11 patients was clinically symptomatic, suggesting most cases represent colonization rather than infection 5
- Asymptomatic MRSA bacteriuria may clear spontaneously without treatment 5
Potential Harms of Unnecessary Treatment
- Treatment of asymptomatic bacteriuria promotes antimicrobial resistance 3
- Unnecessary antimicrobial use results in adverse drug events and increased healthcare costs 3
- Treating asymptomatic bacteriuria may eliminate protective bacterial strains that prevent colonization with more pathogenic organisms 1
Monitoring Recommendations
- Routine urine cultures are not recommended for asymptomatic patients 6
- Routine dipstick testing should not be used to screen for asymptomatic bacteriuria 1
- Pyuria is common in catheterized patients and has no predictive value in differentiating symptomatic UTI from asymptomatic bacteriuria 1
In conclusion, current evidence strongly supports not treating asymptomatic MRSA bacteriuria at >100,000 CFU/mL unless the patient is pregnant or undergoing urological procedures with mucosal bleeding. Treatment of asymptomatic bacteriuria contributes to antimicrobial resistance without providing clinical benefit.