Effect of Sodium Chloride on Surface-Associated Motility of Acinetobacter baumannii and the Role of AdeRS Two-Component System

Abstract

Acinetobacter baumannii is an important bacterial pathogen whose resistance to antibiotics is a growing concern worldwide. Among a wide array of resistance mechanisms displayed by A. baumannii, energy-dependent efflux of antibiotics by proteins belonging the resistance-nodulation-division family serves as an important one. AdeABC pump has been shown to be active in various clinical isolates. Regulation of this pump is controlled by the AdeRS two-component system. In this study, we show that the AdeRS system, in addition to modulating A. baumannii's antibiotic susceptibility, also plays a role in biofilm formation as well as surface-associated motility. We also show that AdeRS deletion mutant is more sensitive to saline stress. In particular, motility of A. baumannii ATCC17978 on agar surface is severely hampered at higher salt concentrations when AdeRS system is absent. Therefore, our study shows that AdeRS could be part of the A. baumannii adaptation strategy to salinity stress.

Roles of Efflux Pumps from Different Superfamilies in the Surface-Associated Motility and Virulence of Acinetobacter baumannii ATCC 17978

“…Although our study does not include an analysis of the AdeB protein, we analyzed the permease encoded by the gene A1S_2736, which has 99% identity with AdeJ of A. nosocomialis, and obtained the same results. Previous studies showed that the absence of the gene encoding the AdeRS two-component system, which regulates the RND efflux pump AdeABC in A. baumannii, causes a loss of motility but not of virulence (25). Further alterations in the motility and virulence of A. nosocomialis resulting from the deregulation of efflux pumps have also been demonstrated.…”

Coping with low water activities and osmotic stress in Acinetobacter baumannii: significance, current status and perspectives

“…Another two‐component system which is related to osmotic stress as well as antibiotic resistance is AdeRS. The role of AdeRS in the regulation of the AdeABC efflux pump is well established, and lately it was shown that an adeRS deletion mutant is more sensitive to osmotic stress, especially when it comes to motility on agar plates with high levels of NaCl or sucrose (De Silva and Kumar, ). This is in line with the osmo‐sensitive phenotype of an emrB (part of the efflux pump EmrAB) (Lin et al ., ) and an abeD (RND‐type transporter) deletion mutant (Srinivasan et al ., ).…”

A response regulator protein with antar domain, AvnR, in Acinetobacter baumannii ATCC 17978 impacts its virulence and amino acid metabolism

“…Deletion of avnR was created using the homologous recombination method as previously described [20]. An unmarked deletion of avnR was achieved using the Flp recombinase and the FRT sites to excise the Gm R marker as previously described [21] and the strain was termed AB104.…”