Understanding antimicrobial activities of phytochemicals against multidrug resistant bacteria and biofilms

New sources of antimicrobial products need to be identified due to the existence and constant evolution of resistant microorganisms and phenotypes, the emergence of new diseases, and the toxicity of some of the current antimicrobials. Development of bacterial resistance, including multidrug resistance (MDR), is unavoidable because it represents a particular aspect of the general microbial evolution. Due to the increased bacterial resistance to conventional antimicrobials, new products need to be discovered and developed. In this context, phytochemicals have already demonstrated their potential as antibacterials when used alone, and as synergists/potentiators of less effective antibacterial products. Moreover, recent studies have demonstrated that phytochemicals can be used where bacterial resistance mechanisms, such as MDR, make conventional treatments ineffective and also in the control of biofilms. The aim of this review is to cover the recent advances in phytochemical antibacterial activities and their mode of action, as well as to indicate current developments in their control of MDR bacteria and biofilms.