Dissemination of OXA-23/NDM co-producing Acinetobacter baumannii in northern Paris hospitals: inter-hospital transmission and screening gaps.

Carbapenem-resistant Acinetobacter baumannii (CRAB) are rare in France and are usually reported in intensive care units (ICU). In 2021/2022, an unexpected increase in the incidence of CRAB isolates co-producing OXA-23 and NDM carbapenemases (OXA-23/NDM-CRAB) in several hospitals in the north of Paris prompted a common retrospective investigation. These strains were extremely resistant to both first- and second-line antibiotics, resulting in difficult-to-treat infections. We collected all cases of OXA-23/NDM-CRABs infection/colonisation between January 2020 and December 2022 in five northern Paris hospitals. Demographic and clinical data were collected for each patient. Isolates were sequenced using Illumina and representative isolates were sequenced using Nanopore. An OXA-23/NDM-CRAB was detected in 42 patients (mean age 61 years, M/F: 1.3), 58% of whom were hospitalised in a medical ward and 42% in an ICU, within three hospitals. Of these patients, 26% (11/42) were infected with CRAB, while 74% (31/42) were colonised. Two clonal strains spread over one year: ST