Phenotypic and Molecular Characterization of Hypervirulent and Multidrug-Resistant Acinetobacter baumannii Isolated from ICU Respiratory Infections

Abstract

The emergence of hypervirulent strains of Acinetobacter baumannii poses a significant threat in intensive care units (ICU). This study aimed to molecularly characterize hypervirulent A. baumannii strains isolated from ICU patients with respiratory infections. Six strains were isolated from ICU patients over one month. Isolates were identified by phenotypic characterization biochemical properties and 16s RNA sequencing. Antibiotic susceptibility testing was conducted followed by resistance genes detection by PCR. MLST, and PFGE were employed to analyse clonal relationships among strains. Plasmid replicon typing and plasmid transmission frequencies were determined. The isolated strains exhibited diverse clinical manifestations, including acute respiratory distress syndrome (ARDS). Antibiotic susceptibility testing revealed multidrug-resistance phenotype. Molecular analysis revealed a complex genetic landscape of antibiotic resistance genes, including ESBLs and carbapenemases, as well as virulence genes such as ompA, csuE, and exoS. The multiple sequence types indicating genetic diversity among the strains as ST1512, ST622, and ST149 (each type two isolates). Plasmid characterization revealed the presence of diverse replicon types associated with multidrug resistance. This study provides comprehensive insights into the phenotypic, molecular, and epidemiological characteristics of hypervirulent A. baumannii outbark in ICU.

Figure 1

Phylogenetic analysis of hypervirulent Acinetobacter baumannii isolates based on 16s rRNA sequencing.

Figure 2

Comprehensive characterization of hypervirulent Acinetobacter baumannii isolates: antibiotic susceptibility, resistance genes, and virulence factors.

Figure 3

Plasmid characteristics of the conjugants were determined based on the replicon types and plasmid transmission frequencies observed.