Researchers analyzed 104 high-quality clinical genomes, including 46 isolates from Tanzania, Kenya, and Uganda, all retrieved from public sequence repositories, and found that globally disseminated high-risk clones dominate the region while carrying an extensive arsenal of resistance genes on unusually diverse mobile elements.
The team, led by Samweli Y. Bahati and Reuben S. Maghembe, pulled raw Illumina paired-end sequencing data from the NCBI Sequence Read Archive and the European Nucleotide Archive during a retrieval window in November 2025. After quality and contamination screening, 120 candidate datasets yielded 104 confirmed clinical A. baumannii genomes. The East African contingent was heavily skewed toward Tanzania, which contributed 38 isolates, compared with 7 from Kenya and just a single isolate from Uganda. The remaining 58 genomes served as global comparators from Germany, India, China, Australia, Brazil, and Belgium. The authors stress that these counts reflect uneven genome availability in public repositories rather than deliberate sampling design.
Multilocus sequence typing using the Pasteur scheme identified 20 distinct sequence types across the dataset, with ST1 and ST2, corresponding to the internationally disseminated clonal complexes IC1 and IC2, by far the most prevalent. ST1 accounted for 46 genomes, including 33 from East Africa, while ST2 comprised 29 genomes, three of them East African. The higher-resolution Oxford scheme resolved 31 known and 13 novel sequence types, including four novel profiles among the East African isolates alone, a signal of locally circulating lineages that have never been cataloged. Capsular K-locus typing revealed 30 distinct capsular types, led by KL18, and O-locus typing found 10 lipooligosaccharide classes, dominated by OCL1 and OCL5, a diversity the authors attribute to ongoing recombination and horizontal gene transfer at these surface polysaccharide loci.
The pangenome itself proved strikingly open. Clustering of 408,303 genes produced 21,831 gene families, of which 76.44 percent were cloud genes, present in only a small fraction of strains, while persistent core genes made up 13.95 percent and shell genes 9.60 percent. The U-shaped frequency distribution, with peaks at the persistent and cloud extremes, is a classic signature of active horizontal gene transfer and substantial inter-strain variability. A core genome alignment of 280,957 single-nucleotide polymorphisms, referenced to strain ATCC 17978, resolved two predominant, well-supported clades corresponding to ST1 and ST2, with East African isolates interspersed among genomes from Germany, Australia, India, and elsewhere.
That phylogenetic intermixing carries an epidemiological message. Most East African isolates fell within the IC1 and IC2 clades, and several non-African strains were embedded among them, a pattern the authors interpret as multiple independent introductions of globally distributed clones into the region, followed by localized clonal expansion and diversification rather than a single importation event. Tanzanian ST946 isolates clustered tightly within a single IC1 sub-lineage, suggesting successful regional persistence and transmission, while the lone Ugandan isolate, an ST78 strain, grouped with Tanzanian ST78 genomes, hinting at cross-border lineage sharing. The authors caution that the absence of detailed epidemiological metadata prevents definitive reconstruction of direct transmission routes.
The resistome analysis detected 100 unique antimicrobial resistance genes, with individual isolates carrying between 13 and 37. Intrinsic efflux pump determinants dominated: the genes abeS, adeG, adeI, abeM, AmvA, adeH, adeJ, and adeK were each present in all 46 East African genomes. Notably, the intrinsic carbapenemase OXA-69 appeared in 71.74 percent of East African genomes but only 27.59 percent of global ones, while the acquired carbapenemase OXA-23 was detected in 19.57 percent of East African strains but was far more frequent in Germany and China. The potent acquired carbapenemase NDM-1 and the 16S rRNA methylase gene armA, which blocks nearly all clinically relevant aminoglycosides, were present in East African isolates but rarer there than in other regions. The authors emphasize that these are descriptive distribution patterns within the sampled dataset, not formal statistical comparisons.
Mobile genetic elements emerged as a central theme. The study identified 82 unique elements across the dataset, with individual genomes harboring up to 20. In East Africa, ISAba1 was the most frequent, found in 43.48 percent of isolates, followed by Tn6018, IS6100, and ISAba22. One Kenyan isolate from a neonate with sepsis stood out with the highest mobilome count, including a transposon, Tn6061, carrying a cluster of five resistance genes previously described in Pseudomonas aeruginosa, a finding the authors flag as a potential mechanism for interspecies resistance gene transfer in a vulnerable patient population. A random forest analysis of gene co-occurrence linked specific resistance genes with particular elements, such as OXA-69 with Tn6018, but the authors are explicit that these importance scores reflect predictive association, not demonstrated physical linkage, and require validation by complete genome reconstruction.
Plasmid replicon screening added another layer of concern. Three replicon families, R1, R3, and RP, were detected in both regional and global isolates, with the R3 family the most prevalent and diverse in each. In East Africa, 19 unique replicon types were identified, 15 of them within the R3 family. The r3-T60 replicon was the most genetically diverse and carried an extensive array of resistance genes, including AAC(6′)-Ib7, ANT(3”)-IIa, armA, mphE, msrE, sul1, catB8, cmlA5, PER-7, and arr-2, while other R3 types, r3-T45 and r3-T20, were associated with NDM-1. These R3-type plasmids were frequently linked to high-risk clones such as ST1, ST25, and ST1138. The authors note that non-detection of a replicon under their identity and coverage thresholds should not be read as definitive plasmid absence, and that long-read sequencing would be needed to resolve plasmid architecture.
The study has clear limitations that the authors state plainly. It was entirely in silico, with no laboratory validation of resistance or mobilome predictions, and the dataset is unbalanced across countries, with Uganda represented by a single genome. Clinical specimen sources were heterogeneous and partially incomplete in public metadata, precluding niche-stratified analyses. Specimen categories across the full dataset were led by blood and wound or skin and soft tissue samples, 25 each, but source information was missing or unspecified for a subset of genomes.
Even with those caveats, the analysis delivers a regional genomic framework where almost none existed before. A previous literature review cited in the paper found published A. baumannii genomic data for only 18 of 29 resource-limited settings surveyed. The East African genomes analyzed here show populations shaped by global clone importation, local microevolution, and resistance acquisition through mobile elements, and they underscore, in the authors’ words, an urgent need for expanded, region-specific genomic surveillance and targeted intervention strategies to limit the spread of multidrug-resistant A. baumannii in clinical and environmental settings across the region.
Subject of Research: Pangenomic analysis of multidrug-resistant Acinetobacter baumannii isolates from East Africa
Article Title: Pangenomic insights into multidrug-resistant Acinetobacter baumannii isolates from East Africa
Article References: Bahati, S. Y., & Maghembe, R. S. (2026). Pangenomic insights into multidrug-resistant Acinetobacter baumannii isolates from East Africa. Discover Bacteria, 3(1), Article 11. https://doi.org/10.1007/s44351-026-00051-z
Image Credits: AI Generated
DOI: 10.1007/s44351-026-00051-z
Keywords: Acinetobacter baumannii, pangenomics, antimicrobial resistance, East Africa, genomic surveillance, carbapenemases, mobile genetic elements, plasmid replicons, sequence typing, public health, Tanzania, hospital pathogens
News Source: Juliet Wilcox. (October 29, 2026). East African superbug genomes reveal global clones and rare resistance plasmids. Scienmag.
