CHARACTERIZATION OF SECRETED PATHOGENICITY FACTORS FROM Acinetobacter baumannii

GIACONE, L; REPIZO G; MORAN BARRIO J

Congreso; Reunion Conjunta 2020 SAIB-SAMIGE; 2020

SAIB-SAMIGE

Acinetobacter baumannii (Ab) is a nosocomial pathogen, of major concern due to its multi-drug resistance (MDR) and the recent appearance of hyper-virulent strains in the clinical setting. The World Health Organization included Ab as a critical priority pathogen for the development of novel antibiotics. Ab pathogenesis is associated with a multitude of potential virulence factors (VF) that remain poorly characterized. There is growing evidence that outer membrane vesicles (OMV) are used as vehicles for the transport of bacterial proteins that contribute to set up the conditions for the infections. In the present work we studied the physiopathology of the MDR Ab strain AB5075. We focused on the contribution of uncharacterized outer membrane proteins (OMPs) associated to OMVs, especially putative lipoproteins (LP).We conducted a bioinformatic prediction using available datasets to construct a list of proteins putatively acting as secreted VF in AB5075. Seven candidates were selected with predicted in the OM, the periplasm, or secreted into OMVs.The corresponding mutants were obtained from the Manoil Lab collection (1). Physiological and microbiological analyses of the mutants were performed. Similar growth rates and susceptibilities to chaotropic agents were observed indicating no alterations of the OM as a general permeability barrier of the mutants. However, differences in antibiotic susceptibilities were observed. Three of them showed higher levels of biofilm formation and adherence to inanimate surfaces, as well as lower A549 cell adherence and invasion, as compared to WT (2). In silico analysis of the candidate proteins revealed that four of them share high similarity with domains of prokaryotic and eukaryotic proteins that are reported to be involved in secretion, signaling pathways or pathogenesis in other organisms. The rest of the proteins have domains similar to other bacterial proteins involved in biofilm formation, or in hemolytic and phospholipase activities, which are crucial in bacterial colonization and infection. Synteny analysis revealed that the corresponding genes are not encoded within gene clusters directly involved in virulence, such as secretion systems. Rather, some of them are in proximity to genes related to stress response or other virulence processes like capsule formation, thus suggesting probable regulatory functions.Although more work is needed, these results contribute to the understanding of Ab virulence mechanisms, revealing novel possible targets for therapeutic development.1. Gallagher LA et al. 2015. Resources for genetic and genomic analysis of emerging pathogen Acinetobacter baumannii. Journal of Bacteriology, 197(12), 2027–2035. https://doi.org/10.1128/JB.00131-152. Giacone L, et al. “Characterization of outer membrane vesicle-carried proteins as pathogenicity factors from Acinetobacter baumannii”. ISEV 2020 Annual Meeting, Julio 2020.