Analysis of virulence and virulence factors in Acinetobacter baumannii A118.

TOLMASKY M.E.; RAMIREZ M.S.; PENNWELL W.; NIKOLAIDIS N.; ADAMS C.; ARIVETT B.; MUNSON R.S.; BONOMO R.A.; ACTIS L.

Whasington

Congreso; 2013 ASM Biodefense and Emerging Diseases Research Meeting; 2013

American Society for Microbiology

Acinetobacter baumannii (Ab) A118 is a clinical isolate susceptible to most antibiotics used in genetic studies, which makes it an ideal model for genetic studies. In this work we identify potential virulence factors and evaluate its virulence. Genomic comparisons with Ab ATCC 17978 and ATCC 19606 were carried out using MapSolver and BLAST. Acinetobactin production and iron uptake from ferric-acinetobactin were assessed using specific bioassays. The receptor BauA was identified by immunoblot. Virulence was determined using Galleria mellonella killing assays. Biofilm formation was estimated combining the material attached to the walls of tubes and the pellicles on the liquid surface. Cell motility was assessed using semi-solid plates. Analysis of high-resolution restriction maps and nucleotide sequence showed the Acinetobactin Iron Uptake System (AIUS) genetic makeup in Ab A118. Bioassays and immunoblot analyses confirmed that this strain secretes acinetobactin, produces the outer membrane receptor protein BauA, and takes up iron from the ferric-acinetobactin complex. Ab A118 includes all genes involved in adhesion and forms biofilms as the other 2 strains. The motility of strain A118 was similar to that of strain 19606 but lower than that of strain 17978. As strain 19606, Ab A118 lacks a fimbrial protein gene, which could explain the reduced motility. Killing assays showed that strain A118 is less virulent than strains 17978 and 19606. In conclusion, Ab A118 possesses a functional AIUS and forms biofilm but showed reduced motility with respect to one of the model Ab strains, probably due to a fimbrial protein missing. However, this does not seem to be an impediment for virulence since Ab ATCC 19606 shows the same characteristic and is highly virulent. Ab A118 is less virulent than strains ATCC 17978 and ATCC 19606. Experiments are being carried out to determine the molecular basis of its reduced virulence.