Epidemiology of Achromobacter in a French hospital over six years: sample types, species, and antibiotic resistance profiles

ABSTRACT Background Achromobacter are non-fermenting-Gram-negative pathogens, mainly reported in cystic fibrosis (CF), but also responsible for opportunistic infections among immunocompromised patients or in case of healthcare-associated infections. Species identification techniques require specific methods not used in the routine diagnostic laboratories ( nrdA -gene sequencing, MultiLocus Sequence Typing or matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry using in-house databases). As a result, epidemiological data are scarce, particularly outside the context of CF. Methods In this descriptive, retrospective monocentric study, we included all Achromobacter isolates, identified at species-level with accurate reference methods, collected from our 1600-beds University Hospital (Dijon, France) during the period 2018-2023, from patients with (pwCF) or without CF (pw/oCF). Data about sample types, context of detection, culture characteristics (mono or polymicrobial), species distribution and antibiotic resistance profiles were collected. Results In total, 651 Achromobacter strains from 274 patients (including 36 pwCF) were isolated from 570 samples. A wide variety of samples was found and mainly polymicrobial (46% of which associated with Pseudomonas aeruginosa ). Among pw/oCF, Achromobacter spp. were mainly detected in respiratory samples (38.7%). More than 12 species were identified, A. xylosoxidans being the most frequent both in pwCF (44.4%) and pw/oCF (60.5%). Overall, piperacillin-tazobactam was the most effective antibiotic (96.5% susceptibility). In pwCF, resistance rates were significantly higher for meropenem, cotrimoxazole and ceftazidime but lower for imipenem compared with pw/oCF. A. xylosoxidans isolates appeared significantly more resistant to imipenem, ceftazidime and ciprofloxacin than non -xylosoxidans Achromobacter species isolates. Conclusions This study highlights the importance of accurate Achromobacter species identification and of CF status when elaborating treatment recommendations.