This report is a summary of a previously published original publication [1].

Urinary tract infections (UTIs) are frequent reasons for consultation in primary care and the choice of empirical antibiotic therapy is determined by the local resistance patterns of the causative uropathogens. However, in the nationally established passive surveillance for monitoring antibiotic resistance, uropathogens of complicated infections are overrepresented and therefore do not reflect the everyday situation in practice. The aim of this study was to determine the resistance patterns of uropathogens in patients with UTI by means of active surveillance.

Trimethoprim-sulfamethoxazole (TMP/SMX) is recommended by many guidelines for the empirical therapy of uncomplicated urinary tract infections (uUTIs) [2–4]. However, clinicians need to be aware of the local resistance patterns as guidelines ­recommend TMP/SMX only in areas where resistance rates do not exceed 20%. Since urinary cultures are not recommended for uUTI and many doctors refrain from a microbiological analysis of the urine before empirical therapy of uUTI, resistance data from the national passive surveillance (Swiss Centre for Antibiotic Resistances, ANRESIS, www.anresis.ch) may have a significant selection bias, as resistance patterns of uropathogens in urine samples from complicated UTI or recurring UTI are overrepresented. The aim of the study was to determine by active surveillance the resistance patterns of uropathogens in patients with UTI in Swiss primary care.

The study was conducted between June 2017 and August 2018 in 163 primary care practices. Patients ≥18 years of age with the diagnosis of lower UTI (cystitis) could be included in the study. Pregnant woman and patients with pyelonephritis were excluded. A urine specimen, as well as basic clinical and epidemiological data, were obtained from all patients. All urine samples were analysed centrally in one laboratory (laboratory Risch) and in the event of microbial growth, antimicrobial resistance tests were performed. The local ethics committee of Zurich approved the study (BASEC Number: 2016-01918) and all patients signed a study-specific informed consent form.

The final analysis included 1352 patients, of whom 1210 had a diagnosis of uUTI and 129 had a diagnosis of complicated UTI. Overall, 94.9% of the patients were female and the mean age was 53.8 years (standard deviation 20.8). Positive urine cultures were reported for 87.1% of the urine samples. Urine samples with detection of three or more bacteria (140 cases, 11.9%) were considered contaminated and excluded from the following analyses. Gram-negative rods were detected in 86.8% of all samples, gram-positive bacteria (excluding enterococci) in 19.4% and enterococci in 6.9%. Escherichia coli (E. coli) (74.6%) was the most commonly detected single bacterium. No statistically significant differences were found in the distribution of bacteria in ­patients with uncomplicated and complicated UTI. Resistance patterns for E. coli are reported in table 1. We found a high proportion of E. coli isolates to be susceptible to TMP/SMX (85.66%, 95% confidence interval [CI] 85.58–85.74%), nitrofurantoin (99.48%, 95% CI 99.47–99.5%) and fosfomycin (99.35%, 95% CI 99.34–99.37%). Compared with the resistance patterns provided by ANRESIS, we found significant higher rates of susceptibility of E.coli to TMP/SMX and ciprofloxacin (table 1).

In multivariate logistic regression analysis, patient age (odds ratio [OR] 1.01, 95% CI 1.00–1.02; p = 0.042), antimicrobial exposure during the past 3 months (OR 1.84, 95% CI 1.17–2.87; p = 0.007) and a history of recent travel to Africa (OR 3.16, 95% CI 1.24–7.45; p = 0.011) were identified in patients with an uUTI as independent predictors for resistance to TMP/SMX, fosfomycin or nitrofurantoin.

In this study, we determined by active surveillance ­actual susceptibility patterns of uropathogens in ­patients with acute UTI presenting to primary care physicians. Antibiotic susceptibility rates of the most common uropathogen E.coli to the recommended first-line antibiotics were high and we found higher rates of susceptibility as compared with data reported by the national passive surveillance system. With the exception of the Geneva region (76.5%), the proportions of ­E. coli ­isolates susceptible to TMP/SMX were above the 80% margin in our study. However, the number of urine samples studied in the Geneva area was small (n = 17) and therefore this sub-analysis must be considered with caution.

TMP/SMX is therefore an adequate antibiotic for the empirical therapy of uUTI according to the current guidelines [2, 3]. We were able to confirm the risk factors for antibiotic resistance known from the literature [5, 6]. Accordingly, patients with a risk factor (prior antibiotic exposure, or history of recent travel) must be assumed to have a higher resistance rates and an alternative antibiotic can be considered.

Although the susceptibility rates of E.coli to the quinolone antibiotics were high, we must emphasise that quinolone antibiotics should not be used for empirical therapy of uUTI. On the one hand, quinolone antibiotics have a wide range of serious side effects and, on the other hand, the overuse of quinolones in UTI leads to an increase in resistance not only of ­urinary, but also of non-urogenital pathogens. As quinolone antibiotics are of particular importance in the treatment in non-urogenital infections, an increase in resistance rates should be avoided [4]. With TMP/SMX, nitrofurantoin and fosfomycin, three effective and well tolerated alternative antibiotics are available. Accordingly, ­quinolone antibiotics should only be used in selected cases where the use of another antibiotic is contraindicated.