Treatment with aminoglycosides or polymyxin monotherapy was found to be safe and effective for patients with complicated urinary tract infections (cUTI) caused by extensively drug-resistant (XDR) Pseudomonas aeruginosa (PA), according to results of a study published in Infectious Diseases and Therapy.

In this study, researchers reviewed data from all adult patients diagnosed with cUTI caused by XDR-PA at a single tertiary hospital in Spain between 2010 and 2019. The researchers sought to assess the safety and efficacy of aminoglycosides or polymyxin monotherapy vs other antibiotic regimens, including combined antimicrobial therapy, for the treatment of cUTI caused by XDR-PA. The XDR phenotype was defined, and a propensity score was used as a covariate in multivariate analyses and for matching. Early clinical failure and at end of treatment was the primary outcome. Secondary outcomes included 30- and 90-day mortality, microbiologic clearance, and antibiotic-related adverse effects.

Among a total of 465 patients with cUTI reviewed, 101 were included in the final analysis. Of these patients, 48% were treated with aminoglycosides or colistin monotherapy. Susceptibility of XDR-PA to colistin and amikacin was 100% and 43%, respectively. In patients treated with antibiotics other than aminoglycosides or polymyxin monotherapy, there was an increased risk for hematologic malignancy (P <.001), bacteremia (P =.048), and they were more likely to have increased sequential organ failure assessment (SOFA) scores (P =.048).

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Aminoglycoside or colistin monotherapy was not associated with worse outcomes in models adjusted by propensity score. The adjusted odds ratio (OR) for early clinical failure and failure at end of treatment with aminoglycosides was 0.53 (95% CI, 0.18-1.58) and 1.29 (95% CI 0.34-4.38) for polymyxin monotherapy.

Neither therapy was associated with increased 30 or 90-day mortality, or an absence of microbiologic clearance. There were no significant differences observed among the patients in regard to nephrotoxicity, and Clostridioides difficile infections were only in observed in those treated with other antibiotic regimens.

This study was limited by its retrospective design and single-center setting. Other limitations were that many patients in the control group used combinations of aminoglycosides or colistin with other drugs, not all patients had a urine control culture to determine microbiologic clearance, comorbidities were not determined with disease codes, potential misclassification or measurement errors of clinical records, and a lack of genotypic data.

According to researchers, “these results may be useful for antibiotic stewardship activities given their clinical and ecological impact.” They concluded that “… further studies are needed to confirm these findings, particularly in more severely ill patients.”

Disclosure: Some authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


López Montesinos I, Gómez-Zorrilla S, Palacios-Baena ZR, et al. Aminoglycoside or polymyxin monotherapy for treating complicated urinary tract infections caused by extensively drug-resistant Pseudomonas aeruginosa: A propensity score-adjusted and matched cohort study. Infect Dis Ther. Published online December 3, 2021. doi: 10.1007/s40121-021-00570-z