What information is available regarding screening and treating asymptomatic bacteriuria prior to select nonurologic surgeries?
Asymptomatic bacteriuria (ASB) is defined as the presence of bacteria in the urine at a quantity of ≥105 colony-forming units (CFU)/mL or ≥108 CFU/L with no signs or symptoms of a urinary tract infection and without regards to pyuria.1 Asymptomatic bacteriuria is common among healthy women and people with urologic conditions. Studies have shown that ASB is not associated with adverse outcomes in most populations, and it can be difficult to achieve and maintain a sterile urine sample in these patients. In 2005, the Infectious Diseases Society of America (IDSA) published a practice guideline for the management ASB. This guideline recommended against screening for and treating ASB in most cases, with the exception of during pregnancy and prior to invasive urologic procedures.
In patients undergoing nonurologic surgery, preoperative ASB has been linked to adverse outcomes post-surgery, including surgical site infection and urinary tract infection.1 This has become a particular concern for surgeries involving implantation of foreign materials, such as orthopedic joint replacements, vascular surgeries, and cardiac valve replacements, due to the potential for hematogenous spread from the bladder to the surgical site. Due to a general lack of strong evidence on this topic, screening for and treating ASB preoperatively has become common practice over the past 30 years in these elective, nonurologic surgeries. Since the publication of the 2005 IDSA guideline, several studies have examined the value of managing ASB preoperatively. In 2019, the IDSA published an update to the 2005 ASB guideline, which makes recommendations on screening and treatment for specific patient populations, including patients undergoing elective nonurologic surgery. Of note, the guideline provides separate recommendations for patients undergoing kidney transplant, which is outside of the scope of this FAQ.
The updated 2019 IDSA guideline on ASB recommends against screening for or treating ASB in patients undergoing elective nonurologic surgery.1 This is a strong recommendation, based on low-quality evidence. The evidence included in the guideline consists of 3 studies that did not show a benefit with treatment of ASB.2-4 These are outlined in the Table. All studies examine patients undergoing orthopedic surgeries, while 1 study also includes patients with cardiac valve and vascular surgeries. In general, no study found a significant reduction in surgical site infection with treatment of ASB, with one study even showing a statistically significantly higher amount of infections with antibacterial treatment. This study was composed of 96% male patients, which may not be reflective of the typical population affected by ASB. The choice of antibacterial in all studies was generally chosen by the provider or guided by culture isolates. Additionally, the number of surgical site infections that occurred in each study was low; therefore, studies may not have been powered to detect a difference.
|Table. Overview of evidence supporting 2019 IDSA guideline recommendations. 2-4|
|Study/design||Patients||SSI (ASB vs. non-ASB, respectively)*||SSI (ASB treated vs. non-treated, respectively)*||Notes|
|Cordero-Ampuero et al 20132|
Procedure: THA (n=228; 8 with ASB; 3 treated), and HA (n=243; 38 with ASB; 23 treated)
|THA: no infections reported |
HA: 6 vs. 6 patients (bacteria from all wound isolates differed from urine culture)
|Not reported||Abx regimen: Culture specific; all patients also received cefazolin x 48 hours
62% of population female
|Drekonja et al 20133|
Cohort, SC, retrospective
|N=1688 (n=54 with ASB; 16 treated)|
Procedure: Cardiothoracic, orthopedic, and vascular surgery
|20% vs. 16% (p=0.56)||45% vs. 14%; (p=0.03)||Abx regimen: per provider
4% of population female
|Sousa et al 20144|
Cohort, MC, retrospective
|N=2497 (n=303 with ASB; 154 treated)|
Procedure: TKA, THA
|4.3% vs. 1.4% (OR, 3.23; 95% CI 1.67 to 6.27; p=0.001)||3.9% vs. 4.7% (OR, 0.82; 95% CI, 0.27 to 2.51; p=0.78)||Abx regimen: per provider
63% of population female
|* Endpoint evaluated at 3 months (Cordero-Amuero et al), 30 days (Drekonja et al), or 1 year (Sousa et al)
Abbreviations: Abx=antibiotic; ASB=asymptomatic bacteriuria; CI=confidence interval; HA=hemiarthroplasty; IDSA=Infectious Diseases Society of America; MC=multicenter; OR=odds ratio; RCT=randomized controlled trial; SC=single center; SSI=surgical site infection; THA=total hip arthroplasty; TKA=total knee arthroplasty
Following the publication of the updated IDSA ASB guideline, several meta-analyses and studies have been published evaluating the effect of treating ASB prior to surgery. In general, recent evidence aligns with the current IDSA recommendations. This includes 2 meta-analyses related to joint arthroplasty, 1 meta-analysis in cardiovascular surgery, and 1 national cohort study in U.S. veterans undergoing a variety of implantation surgeries.
Gómez-Ochoa and colleagues and Wang and colleagues each published a meta-analysis exclusive to joint arthroplasty following the guideline update.5,6 The meta-analysis by Gómez-Ochoa and colleagues includes 4 studies comparing surgical site infection in ASB patients with or without treatment.5 Out of the 4 studies included, 2 of the studies are referenced by the ASB guideline (Sousa et al 2014 and Cordero-Ampuero et al 2013), while 2 studies are not included in the guideline. In a pooled analysis of the included studies, there was not a significant difference in surgical site infection between ASB patients treated with antibacterial therapy versus not-treated (1.67% [8/477] vs. 1.11% [14/1261], respectively; odds ratio [OR], 0.82; 95% confidence interval [CI], 0.33 to 2.04). The meta-analysis by Wang and colleagues included 3 studies, all of which were unique from the guidelines and the meta-analysis by Gomez-Ochoa and colleagues.6 A pooled meta-analysis of these studies also found no significant difference between treating and not-treating patients with ASB (3.76% [7/184] vs. 4.55% [8/176], respectively; risk ratio [RR], 0.89; 95% CI 0.36 to 2.20).
Gómez-Ochoa and colleagues also published a meta-analysis examining the treatment of ASB prior to cardiovascular surgery, which included 3 studies not included in the 2019 ASB guideline.7 The meta-analysis failed to show a benefit in treatment compared to no treatment for reducing surgical site infection (12.9% [15/116] vs. 8.2% [82/1000], respectively; OR, 1.38; 95% CI, 0.56 to 3.38).
Finally, the recent multicenter, retrospective, cohort study in U.S. veterans was published by Gallegos Salazar and colleagues.8 This cohort study included 68,265 veterans that underwent cardiac, orthopedic, or vascular surgery requiring implant of foreign materials. Most patients were male (96.2%), and the average age was 64.6 years. A total of 617 patients had ASB, of which 485 received antibacterial treatment active against the isolated pathogen. There was no statistically significant difference between patients that received treatment for ASB and patients receiving no treatment (2.5% vs. 2.3%, respectively; OR, 1.01; 95% CI, 0.28 to 3.65; p=0.99). A subgroup analysis of patients undergoing cardiac surgery showed a trend towards more surgical site infections in patients receiving treatment compared to those not receiving treatment; however, the difference was still not statistically significant (3.3% vs. 2.4%, respectively; OR, 1.71; 95% CI, 0.17 to 16.34).
Evidence examining the benefit of treating ASB is generally low quality, and most available studies are retrospective and have a low event rate. Because of the lack of evidence, treating ASB preoperatively has become common practice. However, the 2019 IDSA ASB guideline recommends against screening and treatment of ASB in patients undergoing elective nonurologic procedures. Although ASB has been linked to an increase in surgical site infections, literature does not show a significant decrease in surgical site infections when ASB is treated preoperatively. The IDSA recommendation is based primarily on studies examining orthopedic, vascular, and cardiac surgical populations, and more recent meta-analyses and studies have aligned with these recommendations.
- Nicolle LE, Gupta K, Bradley SF, et al. Clinical practice guideline for the management of asymptomatic bacteriuria: 2019 update by the Infectious Diseases Society of America. Clin Infect Dis. 2019;68(10):e83-e110. doi: 10.1093/cid/ciy1121
- Cordero Ampuero J, Gonzalez-Fernandez E, Martinez-Velez D, Esteban J. Are antibiotics necessary in hip arthroplasty with asymptomatic bacteriuria? Seeding risk with/without treatment. Clin Orthop Relat Res. 2013;471(12):3822-3829. doi: 10.1007/s11999-013-2868-z
- Drekonja DM, Zarmbinski B, Johnson JR. Preoperative urine cultures at a veterans affairs medical center. JAMA Intern Med. 2013;173(1):71-72. Doi: 10.1001/2013.jamainternmed.834
- Sousa R, Munoz-Mahamud E, Quayle J, et al. Is asymptomatic bacteriuria a risk factor for prosthetic joint infection? Clin Infect Dis. 2014;59(1):41-47. Doi: 10.1093/cid/ciu235
- Wang C, Yin D, Shi W, Huang W, Zuo D, Lu Q. Current evidence does not support systematic antibiotherapy prior to joint arthroplasty in patients with asymptomatic bacteriuria-a meta analysis. Int Orthop. 2018;42(3):479-485. doi: 10.1007/s00264-018-3765-6
- Gómez-Ochoa SA, Espín-Chico BB. Lack of benefit on treating asymptomatic bacteriuria prior to cardiovascular surgery: a systematic review and meta-analysis. Braz J Cardiovasc Surg. 2018;33(6):641-643. doi: 10.21470/1678-9741-2018-0276
Amanda Gerberich, PharmD, BCPS
Clinical Assistant Professor, Drug Information Specialist
University of Illinois at Chicago College of Pharmacy
The information presented is current as August 17, 2020. This information is intended as an educational piece and should not be used as the sole source for clinical decision-making.