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

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^Ox231^/Pas1 in hospital 1 (n = 12) and hospital 3 (n = 13) differing by 0-16 SNPs and ST^Ox1632^/Pas600 in hospital 2 (n = 13) differing by 0-17 SNPs. WGS and epidemiological investigation identified the likely index patient for hospitals 1 and 3 outbreaks as a patient repatriated from hospitalisation in Cape Verde. This patient was not screened for multidrug resistant bacteria carriage during hospitalisation in hospital 1 and was detected positive 5 days after admission to the ICU in hospital 3. All outbreaks were stopped after infection control teams' intervention. This is the first description of OXA-23/NDM-CRAB outbreaks in metropolitan France. The simultaneous dissemination of two clonal OXA-23/NDM-CRAB strains in Parisian hospitals is unusual, particularly in non-ICU settings. Medical and nursing staffs must be sensitized to the importance of screening patients returning from abroad, including for CRAB, to prevent future outbreaks.