ABSTRACT
Efflux pumps are specialized membrane proteins involved in the removal of toxic chemicals from bacterial cells and which are often seen to play a pivotal role in the exclusion of many important clinically relevant drugs, with concomitantly developed antibiotic resistance to the bacterial cell. Almost all bacterial species bear codes for efflux pumps in their chromosomes or movable genetic components like plasmids. They may be tailored to a particular substrate or exported to a large range of substrates with varying structural features. The emergence of multi-drug resistance (MDR) is also linked to efflux pumps that can export many classes of antibiotics or other drugs and is evident in the case of MDR reported in several key pathogenic bacteria such as Acinetobacter baumanni, Enterococcus faecium, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Vibrio cholerae, and so forth. Several reports have revealed that biofilm formation, the phenomenon of the aggregation of planktonic microorganisms where cells are often embedded within a cage-like surface-structure surrounded by self-produced extracellular polymeric substances (EPSs), is associated with the activity of efflux pumps. Efflux pumps have impacts on quorum sensing (QS) regulation that influences biofilm architecture and diversification, as well as the expression of a multitude of virulence factors. Moreover, efflux pumps could potentially affect biofilm formation by increasing the extrusion of QS molecules. Considering the impact of efflux pumps and their potential action on the effectiveness of different drugs, the present discussion focuses on detailed evaluation of efflux pumps and their functionality in mounting multi-drug resistance in bacterial communities in agreement with biofilm conformation and its differentiation.
