Introduction

The increasing rate of antibiotic resistance in uropathogens, especially in Escherichia coli and Klebsiella pneumoniae as the most common etiologic agents of urinary tract infections (UTI), leads to difficulties in selecting adequate empirical therapy and achieving treatment success¹. Since sulfonamide and penicillin were introduced into clinical use in the 1930s and 1940s, respectively, people was motivated by the illusion that infectious diseases were totally controlled by antibiotics. The widespread use of antibiotics, however, imposes strong selection pressure for the development of antibiotic resistance, a major, present-day public health problem². In recent years, the problem has worsened due to the emergence of extended-spectrum beta-lactamases (ESBL), which mediate resistance to b-lactam antimicrobials, especially the third-generation cephalosporins among these organisms. Genes responsible for ESBL production arise by point mutation at the active site of the earlier b-lactamases and are usually plasmid mediated. In addition, ESBL-positive and Gram-negative bacteria often carry genes that confer high levels of resistance to many other antibiotics³.

A summary of several international surveillance systems that have reported uropathogenic E. coli resistance to selected antibiotics in North and South America and Europe reports that there is considerable local variation in resistance. Resistance to ampicillin and trimethoprim ranges from 80% and 61% in Mexico to 33% and 9% in Quebec. In Mexico, resistance to ciprofloxacin has been reported at 72%⁴.

There are many reports in the literature describing the epidemiology of bacterial resistance; however, the microbiologic profile varies from place to place. At our institution, there are no reports on antibiotic resistance and susceptibility trends. The aim of this study was to examine the epidemiological data obtained from isolated bacteria in urine samples from patients at our hospital over a 1-year period. Data included the susceptibility, resistance, and prevalence of ESBL-producing bacteria and fungi.

Methods

A cross-sectional study was carried out with results from urine samples obtained from hospitalized and outpatients at the Western National Medical Center in Jalisco, Mexico, from August 2014 to July 2015. Samples were processed and analyzed in the Hospital's Microbiology Laboratory. The presence of †10⁵ colony-forming units/mL in urine culture (UC) media was considered significant for UTI. Isolated bacteria and antibiotic susceptibility were identified by standard laboratory techniques or an automated system (Vitek, Biomerieux^®) as required.

Inadequate urine samples were excluded from the study: those not processed 1 h after collection, insufficient urine, or urine that was not well labeled. Results with more than 3 pathogens were also excluded.

The Microsoft Excel^® program was utilized to analyze data to obtain demographic data from patients such as gender and age (averages and ranges). The prevalence and percentages of sensitivity and resistance were calculated with basic arithmetic operations. The study was approved by the Institutional Ethics Committee with registration number R-2015-1310-185.

Results

Discussion

Escherichia coli is the most prevalent facultative Gram-negative bacillus among human fecal flora, usually inhabiting the colon as the innocuous commensal. UTI comprises the most common form of extraintestinal E. coli infection, and E. coli is the most common cause of UTI. At some point during their lives, at least 12% of men and 10-20% of women experience an acute symptomatic UTI, and an even greater number develop asymptomatic bacteriuria⁵. The susceptibility of uropathogens to various antibiotics or antibiogram profiling may aid in improving the treatment of UTI without any delay. However, there are many microorganisms responsible for UTI. Among these, some with a high rate of resistant ESBL species have gained much attention⁶. In 2011, Molina-López et al.⁷ analyzed antimicrobial, serotypes, and phylogenetic groups among strains of E. coli isolated from outpatients with UTI in Mexico City. Among the 29 identified serotypes, the most frequent was 025:H4 (21.2%), which has been associated with multidrug resistance and a high virulence potential.

The uropathogenic strains expressed resistance rates as high as 83% for ampicillin and the lowest resistance rate was for meropenem, with 0.85%⁷. Our work does not identify the serotypes; however, we can add that 67.28% of isolated bacteria were E. coli, finding the highest index of resistance for ampicillin, with a percentage similar to the resistance reported by Molina-López et al. (83 vs. 82.6%)⁷. With regard to quinolones and trimethoprim/sulfamethoxazole, our study reported higher resistances.

In another study reported in 2015 by Paniagua-Contreras et al. in Mexico, nearly 48% of E. coli strains were resistant to cephalothin, 97.4% to ampicillin, and 72.7% for cefotaxime; of 188 isolated strains, 96.9% were resistant to at least 3-11 of the antimicrobials studied⁸.

Miranda-Estrada et al. reported, in 2015, an analysis performed on 107 isolates of E. coli at two locations in Mexico. Resistance to ampicillin and trimethoprim/sulfamethoxazole was 92.5 and 70.1%, respectively⁹.

López-Banda et al. analyzed antibiotic resistance in 108 isolated E. coli obtained from 2008 to 2010 in Mexico City. Approximately 20% of the isolates registered the presence of b-lactamases. The authors did not report a statistical relationship between multiresistance and phylogenetic group¹⁰.

Table 7 presents the comparison of our work with the aforementioned studies conducted in Mexico.

With regard to data on resistance to antibiotics in North America, Foxman⁴ presented a review in 2010. Table 8 demonstrated the comparison of our study with that reported by Foxman.

The Antimicrobial Resistance Epidemiological Survey on Cystitis study was conducted in nine countries in Europe, as well as in Brazil, to determine the susceptibility of the major uropathogens circulating in the communities of these geographic areas¹¹. The authors reported that not all sites exhibited the same susceptibility profile, with some countries less affected by resistance problems than others. In Germany, Hungary, Poland, and the Netherlands, > 90% of strains were susceptible to fosfomycin, mecillinam, nitrofurantoin, and ciprofloxacin. Susceptibility rates varied widely among countries for ampicillin (32.7-65.5%), amoxicillin/clavulanic acid (51.9-93.5%), cefuroxime (73-93%), and trimethoprim/sulfamethoxazole (54.5-87.8%)¹².

In terms of E. coli bacterial resistance specifically, there are reports from other countries¹³-¹⁵. Table 9 shows the analysis and the comparison with our results.

Table 10 compares susceptibility profiles between our results and those of other countries¹⁶-¹⁸ regarding general uropathogens.

Our study sheds light on useful data including those antibiotics such as daptomycin and linezolid may be effective in the treatment of multidrug-resistant cases because they exhibited no bacteria resistance. Other medications with a low index of resistance comprised cefotetan, piperacillin/tazobactam, and carbapenems with resistance percentages <10. However, it is prudent to analyze the tables of the results obtained in this study at the time of the empirical treatment indicated, due to that the majority of antimicrobial drugs available for oral administration presented resistance percentages of >50 for the majority of the pathogens isolated.

Conclusions

With the described results, it is possible to define an overall panorama of resistance and susceptibility to antibiotics in our working area. This study may also be submitted as a national projection due to the results reported, and it can be concluded that the spectrum of sensitivity and resistance of uropathogenic bacteria to antibiotics coincides partially with those reported by other sources of information at national and international levels. In addition, it is clear that there is more resistance to antibiotics, in general, in our study population, as in other national studies, compared with other countries. Data tables can be useful for the judicious use of antibiotics in our unit.