Asymptomatic bacteriuria (ASB) is common, especially in older women. Unfortunately, it is also commonly inappropriately treated with antimicrobial agents. Such unnecessary antimicrobial use can be associated with several untoward effects: selection of resistant pathogens, adverse effects such as Clostridioides difficile infection (CDI), increased health care costs, and disruption of normal microbiome (which in the case of the gastrointestinal tract can adversely affect metabolism, digestion, and immunity). The IDSA has published updated guidelines on the management of ASB, which reiterates that routine screening and treatment, with few exceptions, are not recommended.1
The following are selected, highlighted recommendations from this new guideline. Comments by the authors of this review are in italics.
Recommendations: Treating Nonpregnant and Pregnant Women
- In healthy premenopausal, nonpregnant women or healthy postmenopausal women, we recommend against screening for or treating ASB (strong recommendation, moderate-quality evidence).
- In pregnant women, we recommend screening for and treating ASB (strong recommendation, moderate-quality evidence).
- In pregnant women with ASB, we suggest 4 to 7 days of antimicrobial treatment rather than a shorter duration (weak recommendation, low-quality evidence).
There is no evidence that screening and treating nonpregnant women provide benefit. This includes older women and diabetic women. In fact, studies suggest that treating ASB actually is harmful, as it often leads to infection with more pathogenic, more resistant pathogens, which become associated with symptomatic infection.2In this sense, ASB may play a protective role in preventing symptomatic urinary tract infection (UTI) since ASB can effectively interfere with establishment of more virulent, more resistant organisms. In addition, one Cochrane review demonstrated higher rates of adverse events in patients receiving antimicrobial therapy for ASB versus those receiving no therapy.3
On the other hand, current recommendations are to treat pregnant woman with ASB because they are more likely to develop symptomatic infection. Also, some studies have reported an association of ASB with low-birth-weight babies and premature labor. Of interest, however, the guideline does refer to a recent study from the Netherlands, which suggests that nontreatment of ASB is reasonable and safe4; however, the guideline authors felt that further studies were required to substantiate this approach.
Recommendations: Treating Older Patients With Cognitive Impairment or Who Experience a Fall
- In older patients with functional and/or cognitive impairment with bacteriuria and delirium (acute mental status change, confusion) and without local genitourinary symptoms or other systemic signs of infection (eg, fever or hemodynamic instability), we recommend assessment for other causes and careful observation rather than antimicrobial treatment (strong recommendation, very low-quality evidence).
- In older patients with functional and/or cognitive impairment with bacteriuria and without local genitourinary symptoms or other systemic signs of infection (fever, hemodynamic instability) who experience a fall, we recommend assessment for other causes and careful observation rather than antimicrobial treatment of bacteriuria (strong recommendation, very low-quality evidence).
- As indicated by the guideline authors, this recommendation places a high value on avoiding adverse outcomes of antimicrobial therapy such as CDI, increased antimicrobial resistance, or adverse drug effects, in the absence of evidence that such treatment is beneficial for this vulnerable population. Any connection between asymptomatic bacteriuria and mental status changes in older persons is more coincidental than causative.
- The diagnosis of UTI should be made upon the patient presentation and symptomatology (vs urine studies alone), which may prove to be a challenge in older adults who present with nonspecific symptoms such as confusion or those unable to clearly communicate symptoms.5Asymptomatic bacteriuria is especially prevalent in older adults; thus, it is imperative to perform a thorough assessment for other causes of altered mentation or falls before ordering urine studies and antimicrobial therapy. In patients unable to clearly communicate symptoms, physical assessment may prove useful (eg, suprapubic tenderness) in addition to communication with primary caretakers (if applicable) on symptomology and patient's medical history (eg, medication changes, urination habits). Aside from infection, several other conditions may contribute to delirium in older patients, including dehydration, medications, hypoxia, uncontrolled pain, stroke, and environmental changes.6Evaluation for and correction of alternate causes of delirium should be performed in asymptomatic patients to avoid collateral damage of antimicrobials, including adverse effects and increased bacterial resistance, as treatment of ASB may prove more harmful than beneficial. In addition, attributing nonspecific symptoms to bacteriuria without further evaluation for alternative causes may cause delay in diagnosis and treatment of the actual acute issue. One study demonstrated that hospitalized patients with dementia who were treated for ASB had poorer functional outcomes in comparison with ASB patients without delirium who did not receive treatment. Furthermore, although not statistically significant, patients with delirium treated for ASB were more likely to develop CDI versus those who did not receive treatment.7The guidelines place emphasis on the fact that there is insufficient evidence to suggest a causal relationship between bacteriuria and nonspecific presentations (such as change in mental status or falls) in the absence of classic localizing UTI symptoms; thus, treatment in this patient population is nonbeneficial and may even cause harm.1
Recommendations: Treating Patients With Indwelling Urethral Catheter
- In patients with a short-term indwelling urethral catheter (<30 days), we recommend against screening for or treating ASB (strong recommendation, low-quality evidence).
- In patients with long-term indwelling catheters, we recommend against screening for or treating ASB (strong recommendation, low-quality evidence).
It is estimated that bacteriuria occurs at a rate of 3% to 5% per day of catheter placement.1 In patients with short-term catheters, bacteriuria and the subsequent development of symptomatic UTI are infrequent.8 This may be attributed to bacterial suppression via antimicrobials used for alternative indications or catheter removal before bacteriuria formation.1 The longer the duration of urinary catheter retention, the more likely biofilm formation along the catheter is to occur, which will invariably lead to bacteriuria. Studies have demonstrated lack of benefit in treating ASB in catheterized patients.9–11 In addition, treatment of ASB may lead to undesired effects of unnecessary antimicrobials as previously discussed. Thus, urine cultures in catheterized patients should not be obtained in asymptomatic patients or those with nonspecific symptoms such as fatigue or altered mental status.
Recommendations: Treating Patients Undergoing Surgery
- In patients undergoing elective nonurologic surgery, we recommend against screening for or treating ASB (strong recommendation, low-quality evidence).
We find that it has been common practice in many institutions to routinely obtain preoperative urinalysis and urine culture before a nonurological surgical procedures (frequently before prosthetic joint surgery). This guideline recommends against this practice. Several observational studies have found that screening and treating for ASB preoperatively did not reduce postoperative infection rates. Treating ASB in such instances often delays surgery, in addition to the other potential harmful effects of unnecessary antibiotics.
- In patients who will undergo endoscopic urologic procedures associated with mucosal trauma, we recommend screening for and treating ASB before surgery (strong recommendation).
As indicated in the guideline, the risk for infectious complications in face of ASB is high for procedures during which there is breaking open the mucosal lining (eg, transurethral surgery of the prostate or the bladder, ureteroscopy including lithotripsy, percutaneous stone surgery).1 Urological procedures that do not penetrate the mucosal lining (eg, uncomplicated catheter removal/exchange, diagnostic cystoscopy, cystoscopy including removing of internal ureteric stents) are considered low risk for infectious complications. Of importance, the guideline recommends that a single dose of preoperative antimicrobial for patients with ASB is likely sufficient and associated with fewer adverse events than if longer duration is used.
The message from the ASB guideline is clear. There is strong evidence against the use of antimicrobial therapy for the great majority of patients with ASB. Clinicians and patients should be counseled to avoid unnecessary antimicrobial by refraining from ordering a urinalysis and/or culture in patients without genitourinary symptoms with the exceptions of pregnant women and patients undergoing urologic surgery. Because unnecessary antimicrobial therapy can be harmful to patients, avoidance of antimicrobials in this sense can be consider a patient safety issue and a primary principle of antimicrobial stewardship.
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