The Mutation of Conservative Asp268 Residue in the Peptidoglycan-Associated Domain of the OmpA Protein Affects Multiple Acinetobacter baumannii Virulence Characteristics

Abstract

Acinetobacter baumannii is a nosocomial human pathogen of increasing concern due to its multidrug resistance profile. The outer membrane protein A (OmpA) is an abundant bacterial cell surface component involved in A. baumannii pathogenesis. It has been shown that the C-terminal domain of OmpA is located in the periplasm and non-covalently associates with the peptidoglycan layer via two conserved amino acids, thereby anchoring OmpA to the cell wall. Here, we investigated the role of one of the respective residues, D268 in OmpA of A. baumannii clinical strain Ab169, on its virulence characteristics by complementing the ΔompA mutant with the plasmid-borne ompAD268A allele. We show that while restoring the impaired biofilm formation of the ΔompA strain, the Ab169ompAD268A mutant tended to form bacterial filaments, indicating the abnormalities in cell division. Moreover, the Ab169 OmpA D268-mediated association to peptidoglycan was required for the manifestation of twitching motility, desiccation resistance, serum-induced killing, adhesion to epithelial cells and virulence in a nematode infection model, although it was dispensable for the uptake of β-lactam antibiotics by outer membrane vesicles. Overall, the results of this study demonstrate that the OmpA C-terminal domain-mediated association to peptidoglycan is critical for a number of virulent properties displayed by A. baumannii outside and within the host.

Novel Genes Required for Surface-Associated Motility in Acinetobacter baumannii

“…We found the ompA knockout associated with a significant decrease in pellicle formation in ATCC 17978 but not in 29D2. For A. baumannii and a number of other pathogens, OmpA has been identified as a virulence factor [97][98][99]. In our study, the knockout of ompA in both tested strains significantly decreased the mutant's ability to kill G. mellonella.…”

Blp1 protein shows virulence-associated features and elicits protective immunity to Acinetobacter baumannii infection

“…In contrast to biofilm formation and adhesive properties, our study showed the importance of both blp1 variants for the host colonization of respective strains and, in addition, the requirement of the cognate allele for the manifestation of this phenotype in IC I strain. Several studies have demonstrated the allele-dependent variations in virulent properties of bacterial pathogens [19, 28, 29]. Therefore, the Blp1 may possess yet unknown function required for host colonization, different from that mediating the adhesive properties, which appear to be redundant in IC II strain.…”

OmpA Protein-Deficient Acinetobacter baumannii Outer Membrane Vesicles Trigger Reduced Inflammatory Response

“…A. baumannii strain Ab 169 and its ompA deletion mutant were described in a previous study [ 17 ]. OMVs were isolated as described by [ 17 ].…”

“…A. baumannii strain Ab 169 and its ompA deletion mutant were described in a previous study [ 17 ]. OMVs were isolated as described by [ 17 ]. Briefly, 130 mL of bacterial culture in LB medium grown for 20 h at 37 °C was centrifuged for 15 min at 10,000× g at 4 °C.…”

“…After the transfer of selective antibiotic into the OMVs, relevant enzymes hydrolyze it. Recently, we have demonstrated that OMVs isolated from multidrug-resistant A. baumannii strain inactivated ampicillin in the incubation medium [ 17 ]. The cytotoxic and immunomodulatory properties of OMVs secreted by A. baumannii have been also observed [ 7 , 9 , 18 ].…”