Risk Factors for Trimethoprim-Sulfamethoxazole Resistance in Patients with Acute Uncomplicated Cystitis

Abstract

Emerging antimicrobial resistance among uropathogens makes the management of acute uncomplicated cystitis increasingly challenging. Few prospective data are available on the risk factors for resistance to trimethoprim-sulfamethoxazole (TMP-SMX), the drug of choice in most settings. In order to evaluate this, we prospectively enrolled women 18 to 50 years of age presenting to an urban primary care practice with symptoms of cystitis. Potentially eligible women provided a urine sample for culture and completed a questionnaire regarding putative risk factors for TMP-SMX resistance. Escherichia coli isolates were tested for clonal group A (CGA) membership by a fumC-specific PCR. Of 165 women with cystitis symptoms, 103 had a positive urine culture and were eligible for participation. E. coli was the predominant uropathogen (86%). Fifteen (14.6%) women had a TMP-SMX-resistant (TMP-SMX r ) organism (all of which were E. coli). Urinary tract infection (UTI) is one of the most common indications for antimicrobial therapy. Recent studies have demonstrated that fluoroquinolones are increasingly being used instead of trimethoprim-sulfamethoxazole (TMP-SMX) to treat UTIs in ambulatory women, the majority of whom likely have acute uncomplicated cystitis (9, 14, 25). Concurrently, and perhaps consequently, fluoroquinolone resistance among uropathogens is increasing in prevalence (5, 10). Clearly, strategies that can be used to decrease the rate of fluoroquinolone use, particularly for uncomplicated cystitis, are needed.One such strategy is to facilitate the appropriate prescription of TMP-SMX as the preferred agent for the treatment of UTIs in women. The use of TMP-SMX for uncomplicated cystitis is declining (14). The reasons for this are not entirely clear, but a contributing factor may be concerns over the rising rates of TMP-SMX resistance among uropathogens (23). Guidelines for the treatment of acute uncomplicated cystitis recommend the use of alternative agents in settings where TMP-SMX is problematic due to anticipated resistance, intolerance, or other factors (8,26). Unfortunately, local susceptibility data often come from hospital-based microbiology laboratories and may not accurately reflect the prevalence of TMP-SMX resistance among otherwise healthy outpatient women with UTIs, many of whom do not have urine cultures and susceptibilities performed (7). Thus, the actual prevalence of resistance in any given locale is usually unknown or may be overestimated on the basis of hospital-derived data, leading to the unnecessary avoidance of TMP-SMX as a first-line agent.Knowledge of the individual host factors that predict TMP-SMX resistance would allow clinicians to make an informed prescribing decision on a case-by-case basis, eliminating the need to know population-specific resistance rates. Although several studies have attempted to elucidate such individual risk factors, most of those studies have been limited by being retrospective or including mixed gender and age groups that do not fulfill the traditional criteria fo...

Secular Trend and Risk Factors for Antimicrobial Resistance in Escherichia coli Isolates in Switzerland 1997–2007

“…Escherichia coli (E. coli) is the primary UTI pathogen and responsible for 75-90% of cases in the community [3,4]. Most of the relevant studies carried out to date refer to hospitalized patients, and the susceptibility of E. coli varies considerably in different parts of the world [5][6][7][8][9].…”

“…Various studies have shown that E. coli resistance may be predicted by age [4,15,16], male sex [4,15], nosocomial infection [15], traveling habits [3,17], ethnicity [3,18], known malignancies [19], and previous antibiotic treatment [16,20].…”

Predictive Diagnostics for Escherichia coli Infections Based on the Clonal Association of Antimicrobial Resistance and Clinical Outcome

“…Here, the overall prevalences of resistance to trimethoprim-sulfamethoxazole and fluoroquinolones were as high as 35% and 31%, respectively, among the isolates from some of the participating laboratories. Such high resistance rates increase the likelihood of treatment failure if these drugs are used empirically and may cause practitioners to opt for alternative empirical agents, such as nitrofurantoin for cystitis, or a parenteral agent, such as ceftriaxone, gentamicin, piperacillin-tazobactam, or ertapenem for pyelonephritis or urosepsis (20,21). However, nitrofurantoin must be taken for 5 days to achieve the same clinical efficacy that is provided by 3 days of trimethoprim-sulfamethoxazole or fluoroquinolones, and it cannot be used in some patient categories, whereas the parenteral agents are more expensive, hazardous, and inconvenient than oral agents.…”

Community Transmission in the United States of a CTX-M-15-Producing Sequence Type ST131 Escherichia coli Strain Resulting in Death

“…Thus, elicitation of a good medical history, including antibiotic exposures (both direct and indirect), travel, and health care contact, is vital. A future rapid molecular test for relevant multidrug-resistant pathogens, or specific resistance elements, could supplement the careful clinical assessment, allowing more appropriately targeted initial therapy (1).…”