Minor non-fermenting Gram-negative bacilli in Europe, 2020-2024 (MINOFEu)

Abstract

Introduction: Non-fermenting Gram-negative bacilli (NFGNB) other than Pseudomonas and Acinetobacter species remain largely underrepresented in systematic surveillance programs across Europe.

Methods: We conducted a multicentre retrospective observational study analysing all minor NFGNB isolates recovered from blood cultures in 56 European Hospital Centres over a 5-year period (2020-2024). Diagnostic approach, epidemiology and antimicrobial susceptibility according to European Committee on Antimicrobial Susceptibility Testing v. 15.0 were investigated.

Results: A total of 4420 minor NFGNB isolates were included. In 43.6% of cases, the isolates were recovered from polymicrobial blood cultures, and 40.6% were detected during microbiologically defined catheter-related bloodstream infections. Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-ToF) mass spectrometry was the most widely used tool for species identification (98%). Antimicrobial susceptibility testing was conducted in all centres, using mostly broth microdilution commercial systems (57%), disk diffusion (57%) and gradient diffusion MIC strip (54%) methods, mainly according to European Committee on Antimicrobial Susceptibility Testing guidelines (67.9%). The most prevalent species were Stenotrophomonas maltophilia (52.4%), Achromobacter xylosoxidans (7.8%), Sphingomonas paucimobilis (5.3%) and the Burkholderia cepacia complex (4.8%). S. maltophilia displayed a high rate of resistance to sulfamethoxazole/trimethoprim (11%), and 2% of the isolates were found to be likely resistant to cefiderocol. A. xylosoxidans showed high resistance to meropenem (10%), piperacillin/tazobactam (24%) and sulfamethoxazole/trimethoprim (53%) when tested by MIC methods, while showing over 90% susceptibility to meropenem when tested by disk diffusion. S. paucimobilis displayed over 90% susceptibility to amoxicillin/clavulanate, ampicillin/sulbactam, imipenem, meropenem and tetracycline.

Conclusions: This study provides an updated overview of the diagnostic approaches and epidemiology of minor NFGNB across Europe, supporting future comparative analyses and improved diagnostic and antimicrobial strategies.

Keywords: Achromobacter; Antimicrobial resistance; Burkholderia; Non-fermenting Gram-negative bacilli; Sphingomonas; Stenotrophomonas.