# In vitro activity of imipenem/relebactam and comparators against Enterobacterales isolates collected in Brazilian hospitals according to results from the Study for Monitoring Antimicrobial Resistance Trends, 2020–2021

## TL;DR

This study tested how well imipenem/relebactam and other antibiotics work against bacteria collected from Brazilian hospitals, finding that imipenem/relebactam was highly effective.

## Contribution

The study provides new data on antibiotic effectiveness in Brazil, highlighting imipenem/relebactam's strong in vitro performance against resistant Enterobacterales.

## Key findings

- Over 99% of E. coli isolates were susceptible to imipenem/relebactam and other tested antibiotics.
- K. pneumoniae isolates showed the highest susceptibility to ceftazidime/avibactam and imipenem/relebactam.
- Imipenem/relebactam demonstrated comparable or better activity than other drugs against multidrug-resistant isolates.

## Abstract

The Study for Monitoring Antimicrobial Resistance Trends (SMART) surveillance program tested imipenem/relebactam (IMR) and comparators against a total of 2,258 non-duplicate clinical isolates of Enterobacterales (Klebsiella pneumoniae and Escherichia coli) collected across six Brazilian cities during 2020–2021. Antimicrobial susceptibility was determined by the Clinical and Laboratory Standards Institute (CLSI) reference broth microdilution method and interpreted following Brazilian Committee on Antimicrobial Susceptibility (BrCAST)/European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints. Enterobacterales isolates were screened for β-lactamase genes (bla) by sequencing. The most frequent isolates identified among Enterobacterales were E. coli (n = 471; 20.9%) and K. pneumoniae (n = 453; 20.1%). Susceptibility testing showed that >99% of E. coli isolates were susceptible to colistin ([COL], n = 470; 99.8%), meropenem ([MEM], n = 468; 99.4%), IMR (n = 468; 99.4%), and ceftazidime/avibactam ([CZA], n = 468; 99.4%), whereas a high proportion of E. coli multidrug-resistant (MDR) isolates were susceptible to COL (n = 69; 98.6%), CZA (n = 67; 95.7%), MEM (n = 67; 95.7%), IMR (n = 67; 95.7%), and amikacin ([AMK], n = 66; 94.3%). Overall, K. pneumoniae isolates were most susceptible to CZA (n = 414; 91.4%) and IMR (n = 411; 90.7%) and over 86.0% of K. pneumoniae MDR isolates were susceptible to CZA (n = 268; 87.3%) and IMR (n = 265; 86.3%). This study reported that IMR was one of the most effective in vitro β-lactam–β-lactamase inhibitor combinations tested and demonstrated comparable activity to CZA and higher activity than COL against both the Enterobacterales species tested.

As new mechanisms of antibiotic resistance continue to emerge, especially with the rise of carbapenem resistance, this study emphasizes the importance of assessing the current landscape of antimicrobial resistance to identify optimal therapeutic approaches. In this way, the publication of national data is significant for understanding local epidemiology to evaluate new drugs and make the best choice among the antimicrobials available in the hospital environment, both for critically ill patients with resistant bacterial infections.