Effect of iron on expression of efflux pump (adeABC) and quorum sensing (luxI, luxR) genes in clinical isolates of Acinetobacter baumannii

Abstract

Resistance-nodulation-division efflux system (RND) adeABC contributes to intrinsic resistance to various drug classes in Acinetobacter baumannii. Similarly, quorum sensing (QS) plays an important role in the biofilm formation and pathogenicity of this bacterium. The aims of this study were to evaluate the influence of iron limitation on the expression of efflux pump (adeABC) genes and QS (luxI, luxR) system by relative quantitative real-time polymerase chain reaction (qRT-PCR). In addition, DNA sequence and phylogenetic relatedness of biofilm-associated protein (Bap) gene was also investigated. Sixty-five multidrug-resistant isolates of A. baumannii were recovered from ICU patients of three hospitals in Kerman, Iran. The isolates were highly resistant to at least 11 antibiotics (MIC ≥64 μg/mL); however, 87% and 89% were susceptible to colistin and tigecycline, respectively (MIC 0.05 μg/mL) (p ≤ 0.05). We detected the presence of RND efflux pump, QS, and bap genes with the frequencies of 92% (adeA), 61.5% (adeB), 84.6% (adeC), 80% (luxI), 61% (luxR), and 66% (bap), respectively. qRT-PCR analysis showed that in some isolates, expression of both adeABC and luxI/R was increased more than fourfold in the presence of low iron (20 μm), suggesting the additional regulatory role of iron on both efflux pump and QS system. Alignment and phylogenetic analysis on the strong biofilm forming isolates confirmed that the fragments amplified were indeed part of bap gene and deduced sequence was similar to A. baumannii K9B410.

High prevalence of TEM, VIM, and OXA-2 beta-lactamases and clonal diversity among Acinetobacter baumannii isolates in Turkey

“…In this study, we found that all the isolated strains were susceptible to tigecycline and colistin. However, there have been many reports of tigecycline and colistin resistance, which range from 0.6% to 45.8% [18][19][20][21] and 0 to 30.6%, respectively, around the world [22][23][24][25]. Furthermore, colistin resistance was reported to be of 4% in the EARS-Net 2016 report [26].…”

adeABC efflux gene in Acinetobacter baumannii

“…In some studies the adeB gene was found in all clinically isolated strains, while in other studies the rate just was 70% to 75% [13], [14]. By contrast, some studies found that adeA has the highest detection rate in clinically isolated strains [15], [16]. More researchers incline to the view that adeB is the most important gene in adeABC and is most associated with the resistance of A. baumannii [17].…”

New Perspectives on the Use of Phytochemicals as an Emergent Strategy to Control Bacterial Infections Including Biofilms

“…A report of Poole and colleagues [266] suggested that the MexAB-OprM efflux system is of crucial importance in P. aeruginosa survival under iron restrictions, as it is overexpressed under these circumstances. Furthermore, it was demonstrated that iron limitation has positive effects on the expression of both EPs ( ade ABC) and QS genes ( lux I/R) in A. baumannii , suggesting their regulatory role in these systems [267]. A surface protein named Bap, which is involved in A. baumannii biofilm formation (it helps in cell-cell adhesion and biofilm maturation), was also identified in strong biofilm formers in the described conditions [267].…”