Urinary Tract Infection

Asymptomatic bacteriuria. Asymptomatic bacteriuria is defined as ≥10⁵ bacteria/ml in midstream urine on two confirmatory urine cultures in the absence of urinary tract symptoms (Sobel and Kaye). Clinically the distinction between symptomatic UTI and asymptomatic bacteriuria is often difficult. Asymptomatic bacteriuria in older adults is almost always associated with white cells (pus) in the urine (pyuria), making finding the pyuria nonspecific (i.e., it does not distinguish bacteriuria from infection) (Nicolle, 1992). The high frequency of chronic genitourinary symptoms, such as incontinence, and frequency and urgency of urination, experienced by institutionalized older adults makes the interpretation of a positive urine culture difficult. In other words, it is difficult to know whether the symptoms are those of infection or whether they relate to other diseases of the urinary tract, or even are simply changes associated with aging.

The significance of asymptomatic bacteriuria, and therefore its management, is controversial. Studies performed in both community-dwelling and institutionalized older men and women have failed to demonstrate benefit from identification and treatment of asymptomatic bacteriuria (Sobel and Kaye). In several studies, treatment failed to reduce subsequent symptomatic infections, antimicrobial therapy was associated with adverse side effects, and prolonged eradication of bacteriuria was usually not observed. No differences in mortality have been observed between treated and untreated patients (Baldassare and Kaye; Nicolle, 1992). The use of frequent courses of antibiotics in this population, in an attempt to maintain sterile urine, provokes the emergence of resistant organisms and leads to early recurrence (Nicolle, 1993). For these reasons it is currently recommended that asymptomatic bacteriuria not be treated routinely. However, the incidence of post-procedure bacteremia (bacteria in the blood) following procedures involving trauma to the urogenital mucosa is very high in the presence of infected urine (Cafferkey et al.). Therefore, the need for an invasive genitourinary procedure is a clear indication for eradication of asymptomatic bacteriuria in both community-dwelling and institutionalized older adults.

Symptomatic UTIs. The presentation of UTI in ambulatory older adults without indwelling catheters is generally similar to that described for younger adults. In patients with cystitis, irritative lower urinary tract symptoms including pain with urination, frequent and urgent urination, and suprapubic discomfort usually predominate. The presentation of UTI typically includes flank pain and tenderness, and fever. However, frail older adults unable to communicate their symptoms may present with confusion, falls, immobility, deterioration of urinary continence, mental status changes, or reduced appetite. These individuals may lack the ability to mount a febrile response and may even be hypothermic (Baldassare and Kaye). Moreover, not all patients with pyelonephritis report either lower or upper urinary tract symptoms and often may be mistakenly diagnosed with intestinal obstruction, pneumonia, diverticulitis, or ureteral stones. In spite of the potential for atypical presentation of UTI in older adults, UTI rarely causes nonspecific deterioration without fever or localizing genitourinary symptoms (Nicolle, 1992). Individuals with long-term indwelling urinary catheters and UTI may present with suprapubic pain, discomfort or catheter obstruction (Brier).

Symptomatic UTI in older adults should be treated. The choice of antimicrobial agent should be based upon efficacy, adverse drug effects, cost, and emergence of resistance. Initial therapy should be directed by endemic institutional pathogens and anticipated susceptibilities. Trimethoprim-sulfamethoxazole, nitrofurantoin, norfloxacin, and amoxicillin-clavulanate are suitable initial choices with prompt adjustment of therapy based on culture results.

Duration of therapy is not well studied. Many older women with lower UTI will be cured with a three-day course of antibiotics (Baldassare and Kaye; Nicolle, 1992). However, many authorities recommend a seven-day course of therapy for presumed lower UTI in older women (Baldassare and Kaye; Brier). There is no role for short-course therapy of UTI in men. Men presenting with lower UTI symptoms should receive an initial fourteen-day course of therapy (Baldassare and Kaye; Brier). Recurrent UTI in older men frequently represents prostatic infection and should be treated with six to twelve weeks of therapy (Baldassare and Kaye; Blair).

Both men and women presenting with fever and upper urinary tract symptoms should receive a fourteen-day course of therapy (Baldassare and Kaye). Older adults with acute pyelonephritis who appear to be seriously ill or who have structural abnormalities such as stones should be hospitalized for aggressive treatment. Debilitated older patients with UTI are more likely to have bacteria in the blood. Initial antibiotic therapy traditionally includes intravenous ampicillin and gentamicin, but reasonable single-agent alternatives include amoxicillin-sulbactam, ciprofloxacin, and aztreonam. Because elderly patients are more prone to ototoxicity and nephrotoxicity from aminoglycosides, if this agent is used, appropriate alternative agents should be initiated when culture and sensitivity data becomes available, in order to minimize toxicity. A switch to oral antibiotics to complete the fourteen-day course can be made in three to five days when the patient is fever free and improving clinically. Follow-up cultures should be done.

Catheter-associated infections. Older adults remain at high risk of infection as long as they are catheterized. Treating asymptomatic bacteriuria in catheterized individuals is generally not recommended. Symptomatic bacteriuria as manifested by fever and suprapubic pain or discomfort should be treated with systemic antimicrobial agents, which should be selected on the basis of documented prior efficacy, susceptibility, and patient tolerance. Recommended oral agents include trimethoprimsulfamethoxazole and quinolones. If the patient requires intravenous (injection) therapy, ampicillin with an aminoglycoside antibiotic is generally recommended. In order to limit the emergence of resistant organisms and yeast, the duration of therapy is limited to five to seven days. The benefit of routine catheter replacement with initiation of therapy for UTI has not been studied and is currently not recommended (Nicolle, 1994).

Long-term suppressive therapy. Long-term suppressive therapy may be considered in older women with recurrent urinary tract infections (Nicolle, 1992). The antibiotic chosen should be well absorbed, excreted in urine, and inexpensive. It should not alter intestinal flora, should have few side effects, and should have a low incidence of development of resistance. Once-daily trimethoprim-sulfamethoxazole, nitrofurantoin, or norfloxacin are potential options. In older women with recurrent UTI, low-dose oral or intravaginal estrogen has been shown to reduce the frequency of symptomatic infection by restoring intravaginal pH and normal vaginal flora (Nicolle, 1992). Estrogen therapy may be of benefit as an adjunct to antimicrobial therapy in this population. Daily ingestion of cranberry juice has been shown to decrease the occurrence of bacteriuria and pyuria in older women, possibly by decreasing adherence of E Coli to uroepithelium, and may also be a useful adjunct to antibiotics in women with recurrent UTI (Avorn et al.).