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Featured Clinical Topic: Asymptomatic Bacteriuria

23 May 2018 2:02 PM | MSHP Office (Administrator)

Author: Sundus Awan, PharmD: UMKC School of Pharmacy Class of 2018 
Preceptor: Dominick Salvatore, PharmD, BCPS: UMKC School of Pharmacy at MU

In January 2018, the Center for Disease Control (CDC) released a statement on urinary tract infections (UTI’s) to help distinguish the type of infection. According to the CDC, UTI’s are the fourth most common type of healthcare-associated infection, making up more than 12% of the infections reported by acute care hospitals.1 The most common microorganisms associated with UTI’s are Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and other Enterococcus species.2

The Infectious Disease Society of America (IDSA) defines asymptomatic bacteriuria as an isolation of a specified amount of bacteria in an adequate urine sample obtained from a person who does not display signs or symptoms of a UTI. 3 The specified quantitative criteria is at least 100,000 colony-forming units per mL (cfu/ml) of urine in a voided midstream clean-catch specimen and at least 100 cfu/ml of urine from a catheterized specimen.3 The CDC provides a beneficial flow chart which can assist providers in determining the type of urinary tract infection a patient possesses.1

Asymptomatic bacteriuria occurs more commonly in women than in men, with a strong association to sexual activity in younger women. It is rare to find in young men, but the prevalence in men increases after the age of 60 years. Patients with comorbid conditions, such as diabetes, were found to have a higher prevalence of asymptomatic bacteriuria. Patients with short-term indwelling catheters were found to acquire bacteriuria at a rate of 2-7% per day.3

The treatment of asymptomatic bacteriuria is dependent on the patient population. Premenopausal, non-pregnant women with asymptomatic bacteriuria typically clear their bacteriuria spontaneously.4 The IDSA states that women with asymptomatic bacteriuria are more likely to have subsequent episodes. However, the treatment of asymptomatic bacteriuria does not prevent or decrease the frequency of future episodes. Because of this, the IDSA does not recommend screening for, or treating, asymptomatic bacteriuria in this patient population.4 Similarly, the IDSA does not recommend screening for, or treating, asymptomatic bacteriuria in women with diabetes, older patients, patients with spinal cord injuries, or patients with indwelling urethral catheters.4

Patients who should be screened and treated for asymptomatic bacteriuria are women who are pregnant and patients who are undergoing urologic procedures.3 Pregnant women who have asymptomatic bacteriuria are more likely to deliver premature or low birthweight infants and have an increased risk of developing pyelonephritis.4 It has been shown that antimicrobial therapy for asymptomatic bacteriuria in pregnant patients can improve fetal outcomes.4 The IDSA recommends treatment for pregnant women who have asymptomatic bacteriuria with three to seven days of appropriate antimicrobial therapy, such as nitrofurantoin.3,4

The CDC states that most healthcare associated UTI’s occur due to urologic instrumentation.1 Patients undergoing urologic procedures, especially transurethral resection of the prostate, should be screened and treated for asymptomatic bacteriuria.3 Ideally, antibiotic therapy should be initiated either the night before or immediately before the procedure to prevent bacteremia and sepsis.3 Additionally, the antimicrobial therapy should not be continued beyond the procedure, unless an indwelling catheter remains after the procedure.3 For patients who are immunocompromised, such as transplant patients, IDSA currently does not make a recommendation for the screening or treatment of asymptomatic bacteriuria, due to the need for further research.3

In a study done at a community teaching hospital, the overtreatment of asymptomatic bacteriuria in hospitalized patients was assessed to determine the total costs of inappropriate treatment and if the implementation of an educational intervention program was effective in reducing the overtreatment of asymptomatic bacteriuria. The study had three phases: a retrospective pre-intervention phase, the implementation of an educational intervention program, and a prospective post-intervention phase. The educational intervention included a seminar in which six clinical vignettes were presented and guideline recommendations were discussed. It also included pocket cards emphasizing the IDSA guidelines on diagnosis and treatment of asymptomatic bacteriuria. Lastly, the intervention included a letter sent to the hospital attending physicians emphasizing the IDSA guidelines and the importance of minimizing inappropriate treatment of asymptomatic bacteriuria.5

During the pre-intervention phase, 47% of patients were inappropriately treated for asymptomatic bacteriuria with a total cost of overtreatment being $1200. In the post-intervention analysis, 15% of patients were inappropriately treated for asymptomatic bacteriuria with a total cost of overtreatment being $600. There was a significant decrease in the proportion of inappropriately treated patients (p=0.036) between the pre- and post-intervention phases. Of note, it was also found that there were fewer urine specimens collected in the post-intervention phase (p < 0.001).5 These findings support the implementation of an educational program aimed at reducing the overtreatment of asymptomatic bacteriuria.

In summary, if a non-pregnant patient does not show any signs or symptoms of a UTI, but microbial organisms are present in at least two adequate urine samples, the patient would be classified as having asymptomatic bacteriuria.  Pharmacologic treatment is not indicated, in order to prevent the recurrence of subsequent episodes and the development of antimicrobial resistance. However, if symptoms are present, then the patient should be treated according to the IDSA guidelines on treatment of symptomatic UTI’s. Implementation of education programs in hospitals and health-systems may be a beneficial way to reduce the overtreatment of asymptomatic bacteriuria.

References:

  1. Center for Disease Control. Urinary tract infection--catheter-associated urinary tract infection and non-catheter-associated urinary tract infection and other urinary system infection events. Jan 2018.
  2. Sievert DM, Ricks P, Edwards JR, et al. Antimicrobial-resistant pathogens associated with healthcare-associated infections: summary of data reported to the National Healthcare Safety Network at the Centers for Disease Control and Prevention, 2009-2010. Infect Control Hosp Epidemiol 2013; 34(1): 1-14.
  3. Nicolle LE, Bradley S, Colgan R, Rice JC, et al. Infectious Disease Society of America guidelines for the diagnosis and treatment of asymptomatic bacteriuria in adults. Clin Infect Dis 2005; 40:643-654.
  4. Colgan R, Nicolle LE, McGlone A, and Hooton TM. Asymptomatic bacteriuria in adults. Am Fam Phys 2006; 74(6): 985-990.
  5. Chowdhury F, Sarkar K, Branche A, Kim J, et al. Preventing the inappropriate treatment of asymptomatic bacteriuria at a community teaching hospital. J of Comm Hosp Internal Med Pers 2012; 2: 1-6.


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