Molecular epidemiology of carbapenem-resistant gram-negative bacilli in Ecuador

Introduction Carbapenem-resistant gram-negative bacilli are a worldwide concern because of high morbidity
and mortality rates. Additionally, the increasing prevalence of these bacteria is dangerous. To investigate the extent
of antimicrobial resistance and prioritize the utility of novel drugs, we evaluated the molecular characteristics
and antimicrobial susceptibility profiles of carbapenem-resistant Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii in Ecuador in 2022.
Methods Ninety-five clinical isolates of carbapenem non-susceptible gram-negative bacilli were collected from six
hospitals in Ecuador. Carbapenem resistance was confirmed with meropenem disk diffusion assays following Clinical
Laboratory Standard Institute guidelines. Carbapenemase production was tested using a modified carbapenemase
inactivation method. Antimicrobial susceptibility was tested with a disk diffusion assay, the Vitek 2 System, and gra‑
dient diffusion strips. Broth microdilution assays were used to assess colistin susceptibility. All the isolates were
screened for the blaKPC, blaNDM, blaOXA-48, blaVIM and blaIMP genes.
In addition, A. baumannii isolates were screened
for the blaOXA-23, blaOXA-58 and blaOXA-24/40 genes.
Results Carbapenemase production was observed in 96.84% of the isolates. The blaKPC, blaNDM and blaOXA-48 genes
were detected in Enterobacterales, with blaKPC being predominant. The blaVIM gene was detected in P. aeruginosa,
and blaOXA-24/40 predominated in A. baumannii. Most of the isolates showed co-resistance to aminoglycosides, fluoro‑
quinolones, and trimethoprim/sulfamethoxazole. Both ceftazidime/avibactam and meropenem/vaborbactam were
active against carbapenem-resistant gram-negative bacilli that produce serin-carbapenemases.