Molecular and virulence characteristics of carbapenem-resistant Acinetobacter baumannii isolates: A prospective cohort study

Abstract

This study aimed to characterise the molecular features and virulence profile of carbapenem-resistant Acinetobacter baumannii (CRAB) isolates. Clinical CRAB isolates were obtained from blood cultures of adult patients with CRAB bacteraemia, collected between July 2015 and July 2021 in a Korean hospital. Real-time polymerase chain reaction was used to detect 13 virulence genes, genotyping was conducted via multilocus sequence typing (MLST), and a Tenebrio molitor infection model was selected for survival analysis. A total of 170 clinical CRAB isolates harboured the blaOXA−23 and blaOXA−51 genes. MLST genotyping identified 11 CRAB sequence types (STs), of which ST191 was the most predominant (25.7%). Virulence genes were distributed as follows: basD, 58.9%; espA, 15.9%; bap, 92.4%; ata, 86.5%; chop, 7.1%; ompA, 77.1%; pbpG; 93.5%; bfmR, 92.9%; fhaB, 70.6%; abeD, 99.4%; cpaA, 0.6%; lipA, 99.4%; and recA, 100%. In the T. molitor model, ST195 showed a significantly higher mortality rate (73.3% vs. 66.7%, p = 0.015) and ST451 displayed a lower mortality rate (60.0% vs. 73.3%, p = 0.007) compared to counterpart groups. Our findings provided insight on the microbiological features of CRAB blood isolates. A potential framework for using a T. molitor infection model to characterise CRAB pathogen virulence is suggested.