The Impact of Antimicrobial Resistance on the Choice of Antibiotic Therapy for Uncomplicated Cystitis

Michael Sands M.D., MPH&TM, Diane Halstead, Ph.D., Noel Gomez, BA, MS

Infectious Diseases Division, Department of Medicine, University of Florida; PathologyDept., Baptist Hospital and the Pathology Department, Shands Hospital, Jacksonville, Florida
 
Symptomatic urinary tract infections (UTIs), cystitis and acute pyelonephritis are common causes of morbidity, particularly in young otherwise healthy women. It has been estimated that there are 7 to 8 million physician visits per year in the U.S. for cystitis and in excess of 100,000 hospitalizations per year for complicated urinary tract infections. The total annual health care cost of urinary tract infections in the US may exceed $1 billion.

Older recommendations for treatment of lower UTI's had been for 7-10 days of antimicrobial therapy. Subsequent studies had shown that shorter course therapy, including single dose therapy was effective in select populations. The target population for shorter course therapy is afebrile pre-menopausal women, without upper tract symptomatology, not pregnant, without a history of pyelonephritis within the past year, diabetes mellitus, urinary tract structural abnormalities, or immune incompetence, and with urinary tract symptoms of less than 5 days duration. Single dose therapy had been recommended using 3 gms of oral amoxacillin or 1-2 double strength tablets of trimethoprim/sulfamethoxazole. It was felt that single dose treatment would provide reasonably effective therapy, assure compliance, lessen medication side effects, reduce costs and minimize antibiotic effects on the gut flora, while potentially eradicating the infecting organism from the gut and perineum. However, single dose therapy has more recently been shown to have unacceptable outcomes, with eradication failure rates of 15-20% or greater. These failure rates are in large part due to the changing resistance patterns of community isolates of urinary tract pathogens, particularly E. coli. It has been suggested that the community antimicrobial resistance profile be used to define the appropriate agents for empiric therapy of uncomplicated UTIs, using a resistance threshold of >20% to exclude antimicrobial agents. With this in mind, we surveyed the antimicrobial resistance patterns of common urinary tract pathogens in the outpatient setting at 2 major Jacksonville hospital laboratories over the 1 year period of Oct 99 - Sept 00. This data is summarized in table1.

E. coli resistance to ampicillin and trimethoprim/sulfamethoxazole was 20% or greater at both the survey institutions, representing a total of 1023 outpatient isolates tested. Most isolates retained susceptibility to levofloxacin, the class fluorquinolone tested and to cefazolin, the parenteral first generation class cephalosporin tested.

Published data suggests excellent bacterial eradication rates for cystitis treated with 3 days of a fluorquinolone ie. norfloxacin, ciprofloxacin or ofloxacin. Data on single dose oral cefaclor has shown a failure rate of 57%. This has been attributed to the drug's short half life and thus brief bladder presence. There is inadequate published data on single or multidosed regimens using longer half life second generation oral cephalosporins for therapy of cystitis.

Based on the antimicrobial resistance pattern for the last year of over 1000 community urinary tract isolates from 2 major Jacksonville hospitals, a 3 day course of treatment with a fluoroquinolone appears to be the optimal therapy for select women with uncomplicated cystitis.

For further reading on this topic I would recommend:

  1. Warren JW, Aburtyn E, Hebel, JR, et al. Buidelines for antimicrobial treatment of uncomplicated acute bacterial cystitis and acute pyelonephritis in women. Clin Infect Dis 1999;29:745-58.
  2. Echols, RM; Tosiello RL, Haverstock DC, Tice AD. Demographic, clinical, and treatment parameters influencing the outcome of actue cystitis. Clin Inf Dis 1999;29:113-19.
Jacksonville Medicine / February, 2001

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