A multinational team studied Acinetobacter baumannii, tracing its evolution and global spread across decades by integrating historical samples with modern genomes.

Two major genetic elements, including the oxa23 resistance gene, emerged as turning points that dramatically boosted the bacterium’s survival against antibiotics.

The analysis reveals at least four distinct lineages within Acinetobacter baumannii international clone 2, with a fourth group diverging independently and being detected more in recent samples, suggesting a potentially more fit variant.

Researchers used genome sequencing on 226 historical samples from the 1970s to early 2000s and more than 1,000 recent genomes from six continents to build a comprehensive evolutionary tree of Acinetobacter baumannii and map antimicrobial resistance genes.

The findings underscore that antibiotic resistance builds up over time and highlight the need for historical and international collaboration to inform antimicrobial policies and stewardship.

Resistance developed in waves over decades, with about 2005 marking when the international clone 2 lineage became the dominant drug-resistant form worldwide.

The study, published in Microbial Genomics, involved institutions such as the University of East Anglia, Quadram Institute, Université de Sherbrooke, and Universidad Nacional Autónoma de México, among others, illustrating global cooperation in tracking hospital superbugs.