Country-Level Variation in Acinetobacter baumannii Resistance across North America, Central America, and the Caribbean: A Phenotypic and Plasmid Genomic Analysis of ATLAS Surveillance Data, 2000–2021

<ns5:p> Background Antimicrobial resistance (AMR) in the WHO Region of the Americas accounted for an estimated 569,000 associated and 141,000 attributable deaths in 2019. <ns5:italic>Acinetobacter baumannii</ns5:italic> , in particular its carbapenem-resistant form, is a WHO critical-priority pathogen that disproportionately affects critically ill patients and acquires resistance efficiently through mobile genetic elements. Country-level variation in resistance across the Americas remains poorly characterised, and phenotypic surveillance alone does not capture the genomic mechanisms that sustain resistance. Methods We conducted a retrospective analysis of the Pfizer ATLAS surveillance dataset, comprising more than 850,000 clinical isolates collected between 2000 and 2021, focusing on <ns5:italic>A. baumannii</ns5:italic> recovered from eleven North and Central American countries. Phenotypic susceptibility was stratified by country, antibiotic, age group, clinical specialty, and specimen type. Plasmid mobility classification and GC content distributions were compared between representative <ns5:italic>A. baumannii</ns5:italic> assemblies from Canada and Mexico. Results Susceptibility varied across countries, with Canada and the United States retaining favourable profiles and El Salvador, Guatemala, Honduras, and Mexico demonstrating elevated resistance to aminopenicillins, third-generation cephalosporins, and fluoroquinolones. Carbapenem and tigecycline susceptibility remained high across most countries. Isolates were concentrated among patients aged 19–84 years and within Medicine General and Medicine ICU settings. Mexican isolates harboured more plasmids than Canadian isolates across conjugative, mobilisable, and non-mobilisable categories, with conjugative plasmids forming the largest category. The Mexican GC content distribution showed a pronounced low-range density peak compatible with a dominant plasmid lineage. Conclusions <ns5:italic>A. baumannii</ns5:italic> resistance across North and Central America, and the Caribbean shows pronounced country-level heterogeneity that aligns with regional differences in antimicrobial governance and healthcare infrastructure. Plasmid-level findings point to a parallel contrast in mobile genetic architecture between higher- and lower-burden settings. Stratified, multi-level surveillance is required to convert aggregate AMR data into actionable regional insight. </ns5:p>