Phytochemicals produced to combat plant pathogens as a source of novel antimicrobial compounds against multidrug-resistant bacteria

The increasing trend of bacterial resistance to existing classes of major antibiotics for prescribed use has placed considerable emphasis on the development of new efficient antibacterial regimens. Throughout recorded history medications derived from herbal extracts have been harnessed to alleviate the clinical symptoms of all types of illness. Phytochemicals form the basis of a vast array of present day or past medicines and hence exotic plants continue to attract attention for novel drug development. Most compounds that are exploited for therapeutic purposes are synthesized by plants as a constitutive part of their innate defence mechanisms. Substances from infected plants are afforded less attention for potential antimicrobial properties because their production is limited to the period of infestation of a given pathogen. This article aims to shed light on our knowledge of induced defence compounds and to compare this to information available on constitutively expressed compounds extracted from plants. Although induced resistance of plants has attained a growing research momentum, further investigation is merited into, for instance, the continuous and specific interactions between plants and herbivores. Such research will help to address the importance of plant toxins elicited by inducible defence mechanisms to meet the great public health challenge of multidrug-resistant bacteria.