Trends of antimicrobial resistance in patients with complicated urinary tract infection: Suggested empirical therapy and lessons learned from a retrospective observational study in Oman.

Background: Complicated urinary tract infection (cUTI) is defined as an infection associated with structural, functional, or metabolic abnormalities of the genitourinary tract. These infections are caused frequently by multidrug-resistant Gram-negative bacilli. The rapid emergence of extended-spectrum beta-lactamase (ESBL), AmpC, and carbapenemase (CR) producers has made the treatment of such infections increasingly more challenging.

Objectives: The aims of the present study were threefold: to assess the clinical profile, trends in etiology, and antimicrobial susceptibility profile in cUTI over the past 10 years at a tertiary care center in Oman as an interrupted time series on the one hand and to develop guidelines for empirical management of such cases on the other.

Materials and methods: We conducted a retrospective analysis of cUTI in patients presenting at Sultan Qaboos University Hospital over 3 years (2008, 2013, and 2018) covering a span of 10 years. Data were obtained from the patient's electronic records in the hospital information system. Analysis was done using the Statistical Package for Social Sciences program (SPSS), version 23.

Results: Among the 650 cases of cUTI, 284 (44%) were males and 366 (56%) were females, with dysuria being the most common symptom (34%). The biggest risk factor for developing cUTI was diabetes (35%). The predominant pathogen was Escherichia coli (53%), followed by Klebsiella spp. (16%), Enterococcus faecalis (7%), Pseudomonas aeruginosa (7%), Candida spp. (2%), and Enterobacter cloacae (2%). Over the years, E. coli emerged as the predominant ESBL and AmpC producer, Acinetobacter baumannii as the multidrug-resistant bug, and Klebsiella pneumoniae as the major carbapenem-resistant Enterobacterales (CRE) producer. Nitrofurantoin emerged as the most effective drug for cystitis. Aminoglycosides, piperacillin-tazobactam, and carbapenems demonstrated the highest activity with an overall resistance of less than 10%. Higher resistance (30%) was observed against cephalosporins, fluoroquinolones, and trimethoprim/sulfamethoxazole. Analysis of the 10-year trend threw up some unexpected results. As expected, resistance increased from 2008 to 2013. Surprisingly, however, antimicrobial resistance in 2018 was lower against majority of the antimicrobials compared to 2013.

Conclusion: There is a paucity of data for developing evidence-based guidelines management of cUTI. Targeted antibiograms and not cumulative antibiograms are essential for promoting appropriate prescribing and optimizing patient care. The welcome decline in resistance may be attributed cascade reporting, introduction of more ID physicians. Another possibility is increased utilization of fluoroquinolones which spared the other groups of antimicrobials. Judicious heterogeneous mixing of antimicrobials should be spearheaded in both cystitis and pyelonephritis so that there is no undue pressure on one drug. We strongly recommend carbapenem-sparing protocols in treatment of cUTI when anticipating augmented resistance due to AmpC production. Synergistic combinations such as piperacillin-tazobactam plus aminoglycosides/fluoroquinolones may be prescribed. In sepsis, however, carbapenems are the drugs of choice.