Clonal dissemination of drug-resistant Acinetobacter baumannii in Thailand: insights from nationwide molecular typing.

INTRODUCTION: Drug-resistant Acinetobacter baumannii poses a global health crisis, especially in Asia. It has a propensity to become clonally endemic in healthcare settings. However, its clonal distribution in a broad geographic area is unclear. METHODOLOGY: The clonality of A. baumannii was characterized nationwide by collecting 572 drug-resistant A. baumannii from 18 hospitals across Thailand regions between 2017-2018 and genotyping them by random amplified polymorphic DNA (RAPD) polymerase chain reaction (PCR) in association with carbapenemase genes data. RESULTS: The results depicted 12 types of RAPD banding. Strikingly, two types were predominant in all hospitals (79%). Of those, 96% harbored the blaOXA-23 gene. The banding pattern matched the preexisting strain in the institution, suggesting an ongoing nationwide circulation of the resistant clone. Interestingly, a unique banding type was identified in high proportion in two nearby hospitals in the northern region (21%, 53/252). Two isolates with the same banding pattern were also identified in a hospital in Bangkok, suggesting the possibility of transfer between regions. Most of the subset of isolates analyzed belonged to sequence type (ST) 2, the most prominent ST in the Asia-Pacific region. CONCLUSIONS: This study demonstrated continuous dissemination of predominating A. baumannii clones across the country, and the emergence of endemic hospital-specific clones, all with high burdens of blaOXA-23; suggesting a strong selection for these resistance determinants. In addition, genotyping with RAPD can be a simple and cost-effective epidemiological tool with efficient discriminatory power for A. baumannii in developing countries.