Improving the Culture of Culturing: Critical Asset to Antimicrobial Stewardship

To the Editor—We read with interest the study by Mullin et al ¹ to reduce catheter-associated urinary tract infections (CAUTIs) in intensive care units (ICUs). The authors focused on optimizing the use of urine cultures and urinary catheter care. The effort led to a reduction in urine culturing in adult ICUs of 41%–80% and more than one-third in the National Healthcare Safety Network (NHSN) defined CAUTI between 2013 and 2014, without much change in device utilization. Compliance with appropriate testing was not reported. These findings highlight 2 important issues: (1) the link between the NHSN surveillance definition and culturing practices and (2) the importance of appropriate testing for CAUTI as a pillar for antimicrobial stewardship.

Nationally, the NHSN CAUTI definition has been used to evaluate quality initiatives to reduce urinary catheter infectious harm, and these definitions have been linked to financial penalties for underperforming hospitals. However, the reliance of this definition on fever and a positive urine culture makes it susceptible to changes in culturing practices. ² The artificial improvements in NHSN-defined events based on reductions in culturing do not necessarily equate to preventing clinical CAUTIs. They may even provide a false sense of success in combatting CAUTI in ICUs where we have seen little movement. ³ Other measures such as device utilization are not susceptible to testing practices and may better reflect care. ²

Asymptomatic bacteriuria is common among catheterized patients. ⁴ Orders for obtaining urine cultures are influenced by the clinician’s “practice culture.” Practices that utilize “screening cultures on admission,” “standing orders,” or “reflex” urine cultures based on urinalysis results may lead to inappropriate diagnoses and/or antimicrobial use. In addition, clinicians often order urine cultures in catheterized patients based on pyuria, urine odor, color, or turbidity, actions that are discouraged by the Infectious Diseases Society of America guidelines. ⁵ Such actions also increase utilization of additional resources (eg, testing, antibiotics, consultations) and adversely expose patients to unnecessary testing and treatments. ⁶ More importantly, inappropriately obtained urine cultures may lead to the wrong diagnosis. Ensuring that frontline physicians and nurses are aware of the indications for testing as well as the risks associated with inappropriate testing are good first steps to improving care (Table 1). ⁷

TABLE 1 When to Obtain or Not Obtain a Urine Culture in a Patient With an Indwelling Urinary Catheter

We suggest a 2-pronged approach to reducing unnecessary urine cultures in catheterized patients. First, we recommend the establishment of an optimized process for obtaining urinalyses and urine cultures. A thorough review of pathways, order sets, policies, and institutional guidelines is needed to ensure best-practice integration. Such a review must include any orders or testing processes embedded into the electronic medical records. For example, pathways or order sets geared toward specific conditions (eg, pneumonia or congestive heart failure) should avoid incorporating tests such as urine cultures to help curb unnecessary use. Moreover, preoperative urine cultures should be avoided in asymptomatic patients that are not undergoing urologic procedures. Testing in populations with a high prevalence of asymptomatic bacteriuria (eg, the elderly or those with urinary catheters) often results in identifying colonized patients, placing them at risk to be exposed to antibiotics unnecessarily. Reflex cultures in catheterized patients based on abnormal urinalysis results (with no consensus on what constitutes abnormal urinalysis to trigger a culture) are frequently used as a convenience to avoid submitting a second urine sample for culture. However, urinalyses are often performed without clinical suspicion of urinary infection, and discovery of pyuria may lead to unnecessary cultures. Pyuria is a common occurrence in patients with urinary catheters and has a low positive predictive value for bacteriuria. ⁸ Urine cultures based on urinalysis results should only be pursued in symptomatic patients and when CAUTI is suspected in a sepsis workup with no obvious sources. ⁹ Reflex urine cultures, without clinical assessment, may undermine antimicrobial stewardship efforts. The solution is to integrate only established best practices into the work flow, underscoring “no testing without clinical evaluation.”

Second, clinician engagement is of paramount importance in changing a culture of inappropriate testing. Physicians and nurses should be educated on best practices, and clinical leaders should be role models to their peers. ⁷ Culturing stewardship needs to be viewed as a necessity by all stakeholders, and the benefits should be relayed in a language that resonates with the different teams. ¹⁰ For example, “PAN” culturing is frequently used without understanding that certain sites are colonized and that the value of the cultures depend on the suspected site of infection. Infectious diseases specialists and infection preventionists often focus on the risk of Clostridium difficile infection and multidrug resistance. We must also highlight the risk of misdiagnosis, which may better capture the attention of other stakeholders such as hospitalists and intensivists. Antimicrobial stewardship teams should also consider incorporating testing stewardship in their efforts to achieve the correct diagnosis, the optimal antimicrobial choice, and the appropriate duration of antimicrobial use. Short of establishing benchmarks for culturing stewardship to gauge success, periodic audits of urine culture use are necessary to identify trends and provide feedback on performance.

In summary, “improving the culture of culturing” should be viewed as an integral component of antimicrobial stewardship. Such an approach is likely to encourage clinicians to use their clinical judgment in their patient evaluations and to move from a reflexive process to a more reflective one, leading to better care.