Is antimicrobial prophylaxis of urinary tract infections cost effective?

Computer-assisted decision support for the diagnosis and treatment of infectious diseases in intensive care units

Diagnosing nosocomial infections in critically ill patients admitted to intensive care units (ICUs) is a challenge because signs and symptoms are usually non-specific for a particular infection. In addition, the choice of treatment, or the decision not to treat, can be difficult. Models and computer-based decision-support systems have been developed to assist ICU physicians in the management of infectious diseases. We discuss the historical development, possibilities, and limitations of various computer-based decision-support models for infectious diseases, with special emphasis on Bayesian approaches. Although Bayesian decision-support systems are potentially useful for medical decision making in infectious disease management, clinical experience with them is limited and prospective evaluation is needed to determine whether their use can improve the quality of patient care.

Predicting fraction dose absorbed in humans using a macroscopic mass balance approach

A theoretical approach for estimating fraction dose absorbed in humans has been developed based on a macroscopic mass balance that incorporates membrane permeability and solubility considerations. The macroscopic mass balance approach (MMBA) is a flow model approach that utilizes fundamental mass transfer theory for estimating the extent of absorption for passively as well as nonpassively absorbed drugs. The mass balance on a tube with steady input and a wall flux of Jw = PwCb results in the following expression for fraction dose absorbed, F: [formula; see text] where the absorption number, An = L/R.Pw/(vz), L and R are the intestinal length and radius, Pw is the unbiased drug wall permeability, (vz) is the axial fluid velocity, C*b = Cb/Co and is the dimensionless bulk or lumen drug concentration, Cb and Co are the bulk and initial drug concentrations, respectively, and z* is the fractional intestinal length and is equal to z/L. Three theoretical cases are considered: (I) Co less than or equal to S, Cm less than or equal to S, (II) Co greater than S, Cm less than or equal to S, and (III) Co greater than S, Cm greater than S, where S is the drug solubility and Cm is the outlet drug concentration. Solving the general steady-state mass balance result for fraction dose absorbed using the mixing tank (MT) and complete radial mixing (CRM) models results in the expressions for the fraction dose absorbed in humans. Two previously published empirical correlations for estimating fraction dose absorbed in humans are discussed and shown to follow as special cases of this theoretical approach. The MMBA is also applied to amoxicillin, a commonly prescribed orally absorbed beta-lactam antibiotic for several doses. The parameters used in the correlation were determined from in situ or in vitro experiments along with a calculated system scaling parameter. The fraction dose absorbed calculated using the MMBA is compared to human amoxicillin pharmacokinetic results from the literature with initial doses approximated to be both above and below its solubility. The results of the MMBA correlation are discussed with respect to the nonpassive absorption mechanism and solubility limitation of amoxicillin. The MMBA is shown to be a fundamental, theoretically based model for estimating fraction dose absorbed in humans from in situ and in vitro parameters from which previously published empirical correlations follow as special cases.

Prognosis in pyelonephritis: promise or progress?

Prognosis in pyelonephritis, or upper urinary tract infection, is provided. This infection is not responsible for progressive renal disease in young or elderly patients but accounts for frequent febrile episodes in women of all ages and men after the age of 50. Vigorous local immune response develops with the infection, which never succeeds in eradicating bacteria but does limit the infection and provides a diagnostic test: the antibody-coated bacteria test. Emphasis is placed on the need for a localization test for upper tract infection because studies based exclusively on clinical criteria are invalid. Appropriate therapy for mildly ill patients is given with recommendations of combination therapy for severely ill persons. Long-term follow-up is critical because most patients with recurrent infections can be given preventive therapy without subjecting them to needless urologic evaluation.

Utility of urine cultures in the emergency department

Urinary tract infection (UTI) is a common problem treated by emergency physicians. A midstream urine sample remains the most frequent method of culture collection. Although midstream urine culture growing more than 10(5) colony-forming units per milliliter (cfu/mL) has been considered diagnostic of UTI, high false-positive and false-negative rates as well as a lack of precision have been associated with this method of collection. Alternative methods of establishing the diagnosis of UTI have excellent sensitivity and may be utilized at the time of patient presentation. These include the detection of leukocyte esterase activity in urine and the presence of one or more bacteria on microscopic examination of an unspun urine sample. Women of child-bearing age represent the vast majority of patients seen with UTI. Uncomplicated infection of the urinary tract has a generally benign course in these patients, and is rarely associated with long-term complications. In addition, these patients are infected with a predictable spectrum of uropathogens that respond to the commonly used antibiotics. It appears that urine cultures provide little additional information in this patient population. Urine cultures should be obtained in patients at high risk for pyelonephritis or bacteremia/urosepsis, as well as in those expected to have uncommon or resistant organisms.

Acute cystitis: a prospective study of laboratory tests and duration of therapy

The efficacy of single-dose therapy with trimethoprim-sulfamethoxazole (TMP-SMZ) and the cost-effectiveness of routine urinalyses and cultures were studied in a prospective randomized trial of 200 women who presented with symptoms of acute lower urinary tract infection. Without the physician's knowledge of the results of urinalysis or culture, the patients were randomly assigned to receive either a single dose or a 10-day multiple-dose course of TMP-SMZ and were followed up for 6 months. Of the 136 patients with positive urine cultures, 68 received single-dose therapy with TMP-SMZ--10 of whom had relapses--and 68 received multiple-dose therapy with TMP-SMZ--only 2 of whom had relapses (P less than 0.02). Fifteen patients in each treatment group experienced reinfection. Side effects of rash and vaginitis were more common in patients who received multiple-dose therapy, but they were mild and well tolerated. Of the 51 patients with urethral syndrome, 48 became asymptomatic after therapy. None of the following tests predicted treatment outcome: pretreatment urinalysis, urine culture or susceptibility testing, antibody-coated bacteria testing, or routine follow-up urinalyses or urine cultures. Empiric therapy with TMP-SMZ in selected women with symptoms of acute uncomplicated urinary tract infection seems practical, safe, and cost-efficient. Considerable savings can be achieved by reserving urinalyses and urine cultures for patients with persistent or recurrent symptoms. Higher cure rates can be expected in patients who receive a standard 10-day course of therapy with TMP-SMZ compared with those who receive single-dose therapy with TMP-SMZ.

Prevention of urinary tract infections

Potential candidates for measures designed to prevent urinary tract infections include (1) women (or girls) with frequent exogenous reinfections; (2) pregnant women; (3) hospitalized patients with short-term indwelling catheters; (4) men with chronic bacterial prostatitis; (5) patients with neurogenic bladders being managed with either intermittent catheterization or chronic indwelling catheters; and (6) men undergoing urologic surgery. Patients in the first three categories represent the vast majority of men and women with preventable urinary tract infections. On the basis of our current understanding of the pathogenesis of urinary infections in women, potential preventive measures can be envisioned. To date, the most successful methods in susceptible women include continuous low-dose antimicrobial prophylaxis or postintercourse antibiotic prophylaxis. In controlled clinical trials, the efficacy of low-dose trimethoprim-sulfamethoxazole, trimethoprim, or nitrofurantoin has repeatedly been demonstrated, and the cost effectiveness of this approach has also been established. An alternative strategy, intermittent, self-administered, single-dose antimicrobial therapy, may be useful in selected circumstances. Screening of high-risk patients for asymptomatic infections has largely been abandoned except in pregnant women in whom this practice remains an important preventive measure. Exciting newer approaches to prevention based on studies clarifying the fimbrial structures mediating bacterial adherence to receptors on uroepithelial cells include the use of receptor analogs and immunoprophylaxis, but these approaches are not yet of demonstrated clinical efficacy.

Urinary tract infection in women. New perspectives on office management

Symptomatic urinary tract infection is a common complaint in women. A convenient classification of such infection is bacterial pyelonephritis, bacterial cystitis, and "urethral syndrome," on the basis of symptoms and urine culture colony count. Pyelonephritis can be treated in the office if the patient is not toxic, follow-up is possible, and the patient can tolerate oral medication. Treatment commonly is given over a period of two to six weeks. Single-dose therapy is now the preferred treatment for bacterial cystitis, and several agents are effective. When an infectious agent can be identified in urethral syndrome, antibiotic therapy is useful. Patients in whom an agent cannot be identified may be found to have interstitial cystitis. Recurrence can be a matter of relapse but usually results from reinfection. The causes of relapse usually can be approached surgically, while reinfection must be treated with behavior modification and prolonged antibiotic prophylaxis.

Single-dose amoxicillin therapy with follow-up urine culture. Effective initial management for acute uncomplicated urinary tract infections

To learn whether a single dose of amoxicillin is safe, effective therapy for acute uncomplicated urinary tract infections, 388 symptomatic nonpregnant women were randomly grouped to receive oral amoxicillin, either as a single 3 g dose of 250 mg three times a day for two weeks. Patients had quantitative as well as dip-slide cultures of urine and tests for antibody-coated bacteria in urine. Follow-up urine cultures were obtained one week after completion of treatment. Results of antimicrobial susceptibility and antibody-coated bacterial tests did not alter the randomized therapy. Among 162 patients with bacteriologically confirmed infections, cure rates were 60.6 percent (43 of 71) for single-dose versus 73.6 percent (67 of 91) for two-week treatment (p = 0.07). Although more antibody-coated bacteria-negative patients (89.6 percent; 26 of 29) were cured overall, a substantial proportion of antibody-coated bacteria-positive patients were also cured by both single-dose (59.3 percent; 32 of 54) and 14-day therapy (64.6 percent; 42 of 65). There were fewer adverse effects in the single-dose treatment group. We conclude that a single 3 g dose of amoxicillin, with follow-up urine culture, provides safe and effective management for acute uncomplicated urinary tract infections in nonpregnant women.

Clinical management of urinary tract infection

The clinical management of urinary tract infection has changed considerably over the last two decades due to the recognition of several important factors: All urinary tract infections are not the same; in particular, deep tissue infection of the kidney and/or prostate requires a very different form of clinical management than does superficial mucosal infection of the bladder. Consistent with these differences, it is now clear that conventional 7-14 day treatment courses are not ideal for most forms of urinary tract infections; deep tissue infection requires more intensive therapy and superficial mucosal infection needs less intensive therapy. In particular, single dose antimicrobial therapy has been a major advance in the management of the most common form of urinary tract infection--acute uncomplicated urinary tract infection of the adult female; such therapy is safe, effective, inexpensive, and the response provides useful clinical information. The recognition of the etiology of the acute urethral syndrome in most patients (true bacteriuria or Chlamydia trachomatis infection) had led to an effective therapeutic approach to this problem. A logical approach to the problem of recurrent urinary tract infection has emerged that is both cost-effective and clinically effective. Finally, a clearer picture of those populations that would benefit most from anatomical study of the urinary tract has been developed. With these advances, this most common of bacterial infections affecting man throughout his lifespan has become much easier to control.

Urinary tract antiseptics

The urinary tract antiseptics discussed herein have specific advantages and disadvantages. All share a pharmacokinetic fate that makes them effective in treating acute, uncomplicated symptomatic bladder bacteriuria. Nitrofurantoin appears to be the most versatile because it is effective against upper tract infection, recurrent bacteriuria, and as a long-term suppressive agent in children and pregnant patients with only a low incidence of the development of resistance. Methenamine, when used with proper understanding of it pharmacokinetic behavior, is also effective in females with uncomplicated recurrent bacteriuria including those with multiply resistant pathogens, as well as a prophylactic agent in males with recurrent infection. There is little evidence that methenamine combined with mandelic or hippuric acid confers any pharmacologic or therapeutic advantage over the use of methanamine base alone. Nalidixic acid and oxolinic acid, in addition to effectiveness in treating uncomplicated acute lower urinary tract infections, may be effective in some patients with recurrent infections, but requires careful sensitivity monitoring of pathogens for the development of resistance. Finally, in a society whose economic pressures are such that it may not be cost-effective to use sulfamethoxazole-trimethoprim for urinary tract prophylaxis--unless two or more acute infections occur per year--the use of these urinary antiseptics may offer increasing advantages now and in the future.

Update on the treatment of bacterial urinary tract infections

The treatment of urinary tract infections (UTIs) has become a complex problem for the clinical practitioner. An understanding of the pharmacology, pharmacokinetics, and in vivo biological activity of antimicrobial agents is needed, as is an understanding of the variables that may influence patient compliance with medication regimens. Although UTIs are usually treated for 10 to 14 days, shorter treatment schedules of seven to ten days or even single-dose regimens are possible. Guidelines for the treatment of UTIs are presented along with suggestions for increased patient compliance.