Currently, the World Health Organization (WHO) considers antibiotic
resistance a serious threat to the treatment of infectious diseases. Moreover, the WHO
has promoted a complex action plan, based on the slogan “no action today, no cure
tomorrow” to control the occurrence and spread of resistant strains that include
strategic actions for mitigation, prevention and control. In the last 50 years, only three
new classes of antibiotics have been approved by WHO and US Food and Drug
Administration (FDA), among which the third one was only approved this year and
found to be effective against the Gram-negative Enterobacteriaceae group for the first
time after 1962. Keeping all the above facts of continuous emergence of antibiotic
resistance in planktonic bacteria and in their biofilm counterpart, this book chapter has
tried to add some more alternative drug resources by means of natural products, which
could ultimately lead to the betterment of humankind. Several recent studies have
shown that natural products (mainly phytochemicals) exhibit their antibacterial activity
through different mechanisms of action like bacterial membrane damage, inhibition of
virulence factors, quorum sensing signalling, inhibition of enzymes and toxins.
Quorum sensing is a signalling process to regulate the expression of several virulence
factors in both Gram-negative and Gram-positive bacteria via an autoinducing loop.
When a critical bacterial cell density is reached, a complex of the regulatory proteins
and specific signalling molecules enable the autoinduction of the quorum sensor and
the expression of the target genes. Quorum sensing inhibitors (QSIs) interfering with
this regulatory network have either been derived from natural sources viz.
phytochemicals and fungi, or they have been chemically synthesized. In this chapter,
we will summarize the updates from the available literature describing the various QSIs
obtained from natural sources and their role as anti-infective agents. We will also
discuss the feasibility of these sources towards the development of future drugs to cure
systematic infections in the human body.
Keywords: Alternative drug, Antibiotic, Antimicrobial resistance, Anti-infective
agent, Infectious disease, Natural product, Pathogen, Quorum sensing, Quorum
sensing inhibitor, Virulence factor.
