Antibiotic resistance modifying ability of phytoextracts in anthrax biological agent Bacillus anthracis and emerging superbugs: a review of synergistic mechanisms

Abstract

Background and objectives The chemotherapeutic management of infections has become challenging due to the global emergence of antibiotic resistant pathogenic bacteria. The recent expansion of studies on plant-derived natural products has lead to the discovery of a plethora of phytochemicals with the potential to combat bacterial drug resistance via various mechanisms of action. This review paper summarizes the primary antibiotic resistance mechanisms of bacteria and also discusses the antibiotic-potentiating ability of phytoextracts and various classes of isolated phytochemicals in reversing antibiotic resistance in anthrax agent Bacillus anthracis and emerging superbug bacteria. Methods Growth inhibitory indices and fractional inhibitory concentration index were applied to evaluate the in vitro synergistic activity of phytoextract-antibiotic combinations in general. Findings A number of studies have indicated that plant-derived natural compounds are capable of significantly reducing the minimum inhibitory concentration of standard antibiotics by altering drug-resistance mechanisms of B. anthracis and other superbug infection causing bacteria. Phytochemical compounds allicin, oleanolic acid, epigallocatechin gallate and curcumin and Jatropha curcas extracts were exceptional synergistic potentiators of various standard antibiotics. Conclusion Considering these facts, phytochemicals represents a valuable and novel source of bioactive compounds with potent antibiotic synergism to modulate bacterial drug-resistance.

The sporadic resurgence of anthrax in sub-Saharan Africa: intricacies and challenges to controlling a potentially fatal zoonotic disease

“…Improved rapid diagnostic tools, like polymerase chain reactionbased methods, have shortened the time to diagnosis [10] Therapeutics-wise, there's progress in identifying novel compounds against Bacillus anthracis, potentially providing alternatives to traditional antibiotics. Vaccine research has introduced promising candidates with enhanced immunogenicity and fewer side effects than older versions [11] .…”

Plant Spices as a Source of Antimicrobial Synergic Molecules to Treat Bacterial and Viral Co-Infections

“…As observed in Table 2 , the association of plants with antibiotics lead to synergistic effects; this is important, as it allows the administration of lower doses of the industrialized antibiotic, with the same or even higher antibiotic effects, contributing to postponing the phenomenon of resistance. The inhibition of efflux pumps by some phytochemicals consequently avoids bacterial exposure to sub-therapeutic concentrations of antibiotics, which is one of the causes of acquired resistance [ 71 ]. Plant metabolites that favor morphological disruptions on the bacteria cell wall help to decrease the number of functional bacterial cells to be attacked by the antibiotic, as postulated for the synergistic interaction of thymol–ciprofloxacin [ 74 ].…”

“…Flow cytometry was used to show that V. diospyroides’ synergistic action in combination with ampicillin is the result of cell membrane granularity disruption [ 76 ]. Plants can act directly in specific intracellular enzymes or deactivate the production of enzymes produced by bacteria to degrade the antibiotic chemical structure, therefore, helping the antibiotic to enter the bacterium cell to exercise its activity [ 71 ]. The synergic multi-target action of phytochemicals can also influence the production of enzymes necessary for endogenous energy production and protein synthesis.…”