Risk factors and molecular epidemiology of ST2-type carbapenem-resistant Acinetobacter baumannii carrying blaOXA−23−like and blaOXA−51−like genes

Abstract

The emergence and spread of carbapenem-resistant Acinetobacter baumannii (CRAB, A. baumannii ) has raised significant concerns and challenges globally. This study analyzes the risk factors, distribution of antibiotic resistance genes, and virulence genes associated with CRAB infections, and explores the molecular epidemiological characteristics of CRAB. The findings provide scientific evidence for the development of prevention and treatment strategies for CRAB. A total of 100 patients diagnosed with A. baumannii (AB) infection through culture and antimicrobial susceptibility testing were included in the study. These patients were classified into the CRAB group and the carbapenem-sensitive A. baumannii (CSAB) group based on their susceptibility to carbapenem antibiotics. Univariate analysis was used to screen for factors associated with CRAB infection, and significant variables were included in a multivariate logistic regression analysis. Additionally, five CRAB strains carrying both bla OXA−51−like and bla OXA−23−like genes were randomly selected for multilocus sequence typing (MLST) and whole-genome sequencing. The analysis included the identification of antimicrobial resistance genes (ARGs), virulence factor genes, pathogen-host interaction annotations from the Pathogen Host Interactions Database, and functional annotations through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Significant differences were observed between the CRAB group and the CSAB group in terms of length of hospital stay ( P = 0.022, OR = 1.068), ICU admission rate ( P = 0.019, OR = 8.032), prior carbapenem use ( P = 0.028, OR = 4.445), and mechanical ventilation use ( P = 0.044, OR = 7.226). In vitro antimicrobial susceptibility testing showed that all CRAB strains were resistant to ceftriaxone, ceftazidime, and ciprofloxacin, with some strains showing resistance to levofloxacin (87.5%) and doxycycline (93.8%), but remaining sensitive to tigecycline and polymyxin B. Through multiplex PCR analysis, we tested 48CRAB strains (carbapenem-resistant A. baumannii ). The results revealed that 41 of these strains carried both the bla OXA−51−like and bla OXA−23−like genes. The presence rate of OXA-type β-lactamase genes and efflux pump genes in randomly selected positive strains is 100%. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation results indicated that the genes of these randomly selected positive strains were primarily involved in cellular processes, metabolic pathways, and environmental information processing, and exhibited strong enzymatic activity and binding functions. Length of hospital stay, ICU admission, prior carbapenem use, and mechanical ventilation are susceptibility factors for carbapenem resistance in A. baumannii infections at this hospital. MLST typing and multiplex PCR analysis indicate the spread of ST2-type bla OXA−51−like and bla OXA−23−like positive CRAB infections in the hospital, with ST2-type CRAB potentially being the dominant clone in circulation. Whole-genome sequencing revealed the resistance and virulence characteristics of CRAB strains isolated from clinical samples at this hospital, and showed that these CRAB strains from the hospital are distinct from those found in different provinces and cities in China.