Acinetobacter baumannii in Germany across human, animal, and environmental settings: a systematic review and secondary analysis of national surveillance data

Acinetobacter baumannii (A. baumannii) is a leading cause of difficult-to-treat healthcare-associated infections worldwide and has been classified as a priority “1” critical pathogen by the World Health Organization. Germany reported 811 mandatory notification cases in 2024, with blaNDM detected in 13% of isolates submitted for carbapenemase typing (49/372 gene-positive notified cases; 95% CI 10.1%–17.0%). No comprehensive One Health synthesis of German A. baumannii science has previously existed. We conducted four parallel systematic literature searches across eleven electronic databases, covering research from January 2019 to June 2026 and guided by PRISMA 2020, to identify peer-reviewed German A. baumannii publications across three domains: animals, environment, and humans, as well as studies that focus on resistance gene characterization. In parallel, Acinetobacter-specific data were extracted from six consecutive yearbooks of RKI’s “Infektionsepidemiologisches Jahrbücher” (2019–2024) on Infectious Disease Epidemiology and compared with the peer-reviewed literature across ten parameters. Thirty-two unique peer-reviewed papers were identified: nine animal, twelve environmental, eight human clinical, and fifteen resistance gene characterization. The blaOXA-23 dominated all six surveillance years at 57–66%. blaNDM surged to 13% of isolates submitted for carbapenemase typing in 2024, with no peer-reviewed characterization of the responsible lineage. Three critical One Health findings emerged: an NDM-1-positive ST25 A. baumannii isolate from an Italian dog processed at a German veterinary laboratory in 2018 predated the 2024 surveillance signal — an epidemiologically unlinked but hypothesis-generating temporal pattern; MDR A. baumannii with clinical-associated MLST profiles was detected in urban wastewater treatment plants receiving hospital wastewater without concurrent patient isolate analysis; and the equine collection contained globally distributed IC1–IC3/ST1–ST3 lineages but did not establish resistance-island identity with German intensive care unit (ICU) strains. No eligible German study simultaneously sampled environmental and human clinical isolates from the same geographic catchment by whole-genome sequencing (WGS). Nineteen research gaps were identified, nine classified as urgent. Germany's animal, environmental, and human clinical A. baumannii research communities operate in parallel without cross-domain genomic linkage. The 2024 blaNDM surveillance signal requires lineage-resolved molecular characterization to determine whether it represents true epidemiological emergence, improved detection, or importation, and to support susceptibility-guided therapy and integrated One Health genomic surveillance.