Two Acinetobacter baumannii Isolates Obtained From a Fatal Necrotizing Fasciitis Infection Display Distinct Genomic...

Area of Science:

• Microbiology
• Infectious Diseases
• Genomics

Background:

• Acinetobacter baumannii is a critical pathogen causing severe infections globally.
• Extensively drug-resistant (XDR) strains and environmental persistence pose significant challenges.
• Limited knowledge exists on A. baumannii virulence in rare infections like necrotizing fasciitis.

Purpose of the Study:

• To investigate the genomic and functional characteristics of XDR A. baumannii isolates from a fatal necrotizing fasciitis case.
• To compare virulence factors and phenotypic traits between isolates obtained at different infection time points.
• To identify potential therapeutic targets by understanding virulence mechanisms in necrotizing fasciitis.

Main Methods:

• Comparative genomic analysis of XDR isolates (NFAb-1, NFAb-2) against reference strains (ATCC 19606T, ATCC 17978).
• Phenotypic assays including biofilm formation, cell viability, flow cytometry, hemolysis, intracellular invasion, and motility tests.
• In vivo infection model using Galleria mellonella to assess mortality rates.

Main Results:

• NFAb-1 and NFAb-2 isolates showed significant genetic divergence from each other and reference strains.
• All strains reduced A549 epithelial cell viability; NFAb-1, NFAb-2, and ATCC 17978 produced less biofilm but more hemolysis and intracellular invasion than ATCC 19606T.
• NFAb-1 and NFAb-2 exhibited distinct motility patterns, with longer pili, and NFAb-1 induced higher mortality in Galleria mellonella.

Conclusions:

• Genomic and phenotypic differences exist between A. baumannii isolates from different stages of necrotizing fasciitis.
• Altered virulence factors, including motility and invasion, may evolve during infection.
• These findings highlight potential shifts in virulence and suggest avenues for novel therapeutic strategies against A. baumannii infections.