The RND Efflux Pump Gene Expression in the Biofilm Formation of Acinetobacter baumannii

Abstract

Multidrug resistant (MDR) Acinetobacter baumannii is a critical opportunistic pathogen in healthcare-associated infections (HAI). This is attributed to several factors, including its ability to develop biofilms that can enhance antimicrobial resistance (AMR) in addition to creating an environment for horizontal transfer of antibiotic resistance genes. The role of the efflux pump in biofilm formation is important for studies on alternative treatments for biofilms. One of the significant efflux pump families is the RND efflux pump family, which is common in Gram negative bacteria. The aim is to study the role of the RND efflux pump in biofilm formation by A. baumannii. The biofilm formation potential of thirty-four MDR A. baumannii isolates was evaluated by crystal violet assays. The effect of efflux pump inhibition and activation was studied using the efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and the RND efflux pump substrate levofloxacin (at sub-MIC), respectively. The isolates were genotypically grouped by enterobacterial repetitive intergenic consensus (ERIC) typing and the expression of adeABC, adeFGH, and adeIJK efflux pump genes was measured by qPCR. Overall, 85.2% (29/34) of isolates were biofilm producers (the phenotype was variable including strong and weak producers). Efflux pump inhibition by CCCP reduced the biofilm formation significantly (p < 0.05) in 20.5% (7/34) of some isolates, whereas sub-MICs of the substrate levofloxacin increased biofilm formation in 17.6% (6/34) of other isolates. Overexpression of the three RND efflux pump genes was detected in five out of eleven selected isolates for qPCR with remarkable overexpression in the adeJ gene. No correlation was detected between the biofilm phenotype pattern and the RND efflux pump gene expression in biofilm cells relative to planktonic cells. In conclusion, the role of the RND efflux pumps AdeABC, AdeFGH, and AdeIJK in biofilm formation does not appear to be pivotal and the expression differs according to the genetic background of each strain. Thus, these pumps may not be a promising target for biofilm inhibition.

Efflux pumps as potential targets for biofilm inhibition

“…Nevertheless, the expression of adeB in A. baumannii clinical isolates has been conflicting. Previous research failed to detect the association between the expression of adeB and biofilm formation in A. baumannii clinical isolates ( Chen et al, 2020 ; Abd El-Rahman et al, 2023 ). Another study conducted by Kim et al (2021) revealed a negative correlation between the expression level of adeB and biofilm formation capacity in A. baumannii clinical isolates (n = 120).…”

“…The AdeABC and AdeIJK efflux pumps belonging to Ade efflux systems are closely associated with antimicrobial resistance in Acinetobacter baumannii ( Abd El-Rahman et al, 2023 ). It has been demonstrated that the deletion of adeB decreased biofilm formation in A. baumannii ( Yoon et al, 2015 ; Richmond et al, 2016 ).…”

Effect of Phenylalanine–Arginine Beta-Naphthylamide on the Values of Minimum Inhibitory Concentration of Quinolones and Aminoglycosides in Clinical Isolates of Acinetobacter baumannii

“…RND-type transporters are known to play a dominant role in the MDR of many Acinetobacter species [ 25 ]. While the overexpression of Ade transporters is often beneficial to bacteria, this is not always the case; some Ade transporters, such as AdeABC, AdeFGH, and AdeIJK, can be toxic to cells when overexpressed [ 26 , 27 ]. Therefore, to assess the role of the drug efflux mechanism in bacteria, efflux pump inhibitors (EPIs) are widely used [ 28 ].…”

Biosurfactant from Nile Papyrus endophyte with potential antibiofilm activity against global clones of Acinetobacter baumannii

“…Hence, A. baumannii is a frequent cause of biofilm-related, particularly catheter-related bloodstream infections (CRBSI) and ventilator-associated pneumonia (VAP) ( Gedefie et al., 2021 ). Such infections are mostly associated with devastating outcomes and are exceedingly resistant to a wide range of antimicrobial treatment modalities, posing a great challenge to infectious disease practitioners ( Mansouri et al., 2013 ; Abd El-Rahman et al., 2023 ; Lafuente Cabrero et al., 2023 ).…”