Molecular evidence of a dominant multidrug resistant Acinetobacter baumannii lineage in a tertiary hospital in northern Peru

Background Acinetobacter baumannii is a major nosocomial pathogen because of its genomic plasticity and capacity to acquire multidrug resistance (MDR), particularly resistance to carbapenems. The World Health Organization classifies carbapenem-resistant A. baumannii as a critical-priority pathogen. Molecular epidemiological data from Latin America remain limited, especially for northern Peru. Methods Drug-resistant A. baumannii isolates collected between 2015 and 2021 at a tertiary referral hospital in northern Peru were characterized by antimicrobial susceptibility testing, BOX-PCR, ERIC-PCR, REP-PCR, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Results All seven isolates met the criteria for MDR, and Ac-4268 showed an extensively drug-resistant phenotype. Repetitive-element PCR identified a group of six isolates with similar banding profiles and a divergent isolate, Ac-4268. Several isolates in the six-isolate group retained susceptibility to one or more aminoglycosides, whereas Ac-4268 was resistant to all antimicrobials tested. The combined molecular and phenotypic findings are consistent with the possible persistence of a dominant related lineage, but they do not establish transmission without whole-genome sequencing and epidemiological linkage data. Conclusion This study provides additional molecular epidemiological evidence on MDR A. baumannii in northern Peru. The findings suggest that a dominant related lineage may have persisted in the hospital alongside a genetically divergent isolate with an extensively drug-resistant phenotype. Confirmation of clonal transmission requires higher-resolution genomic and epidemiological analyses.