RESUMO
OBJECTIVES: To report reference method antimicrobial susceptibility testing results for recent clinical isolates of Gram-negative bacilli from Morocco. METHODS: CLSI (Clinical and Laboratory Standards Institute) broth microdilution antimicrobial susceptibility testing was performed by a central laboratory for isolates of Enterobacterales (n = 810), Pseudomonas aeruginosa (n = 321), and Acinetobacter baumannii (n = 191) collected in 2018-2020 by three hospital laboratories in Morocco. MICs were interpreted using both CLSI (2021) and EUCAST (European Committee on Antimicrobial Susceptibility Testing) (2021) breakpoints. Molecular testing for ß-lactamase genes was performed on isolates meeting defined screening criteria. RESULTS: Most isolates of Enterobacterales were susceptible (CLSI/EUCAST breakpoints) to amikacin (98.0%/96.2%), ceftazidime-avibactam (94.8%/94.8%), and meropenem (92.5%/94.2%). Of Enterobacterales isolates eligible for ß-lactamase gene screening (n = 210), 174 were ESBL-positive, 40 were metallo-ß-lactamase-positive (all NDM), 39 were serine carbapenemase-positive (all OXA); and 7 isolates carried both OXA-48 and NDM-1. Amikacin (89.1%/89.1%) and ceftazidime-avibactam (88.2%/88.2%) were the most active agents tested against P. aeruginosa. Applying CLSI and EUCAST breakpoints, MDR rates were 21.9% and 29.3% for Enterobacterales and 18.4% and 21.8% for P. aeruginosa. Susceptible rates for amikacin, ceftazidime-avibactam, and meropenem were 93.2%/89.5%, 77.4%/82.3%, and 67.8%/80.2% for MDR Enterobacterales and 50.8%/57.1%, 40.7%/45.7%, and 27.1/32.9% for MDR P. aeruginosa. ≥70% of A. baumannii isolates were resistant to all agents tested (except colistin, EUCAST breakpoints only) including amikacin and meropenem. CONCLUSION: Newer ß-lactam/ß-lactamase inhibitor combinations such as ceftazidime-avibactam warrant testing and reporting for Enterobacterales and P. aeruginosa in Morocco given the presence of significant resistance to first-line ß-lactams and fluoroquinolones, pervasive ESBLs and carbapenemases, and toxicity concerns associated with some second-line agents.
