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7.5.1 Interference with Quorum Sensing
Quorum sensing is a communication behavior between single or multiple bacterial
species whereby signal molecules can be produced and detected and coordinated
accordingly in a manner dependent on cell density. As discussed earlier, different
groups of bacteria vary with the quorum sensing system, e.g. Gram negative bacteria have acylhomoserine lactone (AHL), Gram positive bacteria contain autoinducing peptide (AIP), and autoinducer-2 (AI-2) found in both type of bacteria. Quorum
sensing molecules regulate the virulence behaviors of bacterial biofilm. Biofilm
resistance to antimicrobial drugs is now well established as a multicellular approach
that depends essentially on the exchange of chemical signals between the cells.
Quorum sensing quenchers or inhibitors can therefore provide a novel approach by
interfering with bacterial cell-cell communication to prevent the formation of biofilms (Truchado et al. 2015; Algburi et al. 2017).
Several approaches have been developed to interfere with bacterial quorum sensing i.e. (1) competitive binding of inhibitors to the quorum sensing receptors, (2)
inhibition of quorum sensing signals, (3) enzymatic degradation of quorum sensing
signals, and (4) control of quorum sensing genes (Yang and Givskovi 2015). Several
phytocompounds have been explored as quorum sensing inhibitors (QSI); such as
Allium sativum (garlic) crude extracts inhibit the expression of a large number of
quorum sensing controlled genes. Ajoene, a sulfur containing compound found in
garlic extract, has antimicrobial and antibiofilm activity against a number of bacteria, including Escherichia coli, Klebsiella pneumoniae, and Xanthomonas maltophilia (Jakobsen et al. 2012). The efficacy of plant food extracts and phytochemicals
is primarily due to their resemblance to the chemical structure of quorum sensing
signals (Truchado et al. 2015). Quorum sensing inhibitory activity has also identified in Oak bark (Quercus cortex) extract against Chromobacterium violaceum
strain (Deryabin and Tolmacheva 2015). Moreover, eugenol inhibits the production
of quorum sensing mediated violacein in Chromobacterium violaceum and virulence factors in Pseudomonas aeruginosa strains. Eugenol has also found to be
effective against clinical isolates i.e. Listeria monocytogenes and Klebsiella pneumonia (Ta and Arnason 2016). Similarly, methanol extract of Albiza schimperiana
root and petroleum ether extract of Justicia schimperiana seed has also found to
interfere with cell to cell communication of bacterial biofilms (Bacha et al. 2016).
Quercetin, a plant flavonoid, inhibited biofilm formation and quorum sensing regulated characteristics such as violacein inhibition, EPS production and alginate production efficiencies in selected food borne pathogens such as K. pneumoniae,
P. aeruginosa, and Y. enterocolitica (Gopu et al. 2015). Zingerone, a potent antiinflammatory compound found in Zingiber officinale (ginger), also posses potent
effect on quorum sensing signal molecules in clinical isolates of P. aeruginosa
(Kumar et al. 2015) (Table 7.2).
Besides phytocompounds, RNAIII-inhibiting peptide (RIP) has demonstrated
strong activity in preventing methicillin resistant Staphylococcus aureus graft infections in vivo. Actually, Staphylococcus aureus regulates their virulence by using the
B. P. Singh et al.
7.5.1 Interference with Quorum Sensing
Quorum sensing is a communication behavior between single or multiple bacterial
species whereby signal molecules can be produced and detected and coordinated
accordingly in a manner dependent on cell density. As discussed earlier, different
groups of bacteria vary with the quorum sensing system, e.g. Gram negative bacteria have acylhomoserine lactone (AHL), Gram positive bacteria contain autoinducing peptide (AIP), and autoinducer-2 (AI-2) found in both type of bacteria. Quorum
sensing molecules regulate the virulence behaviors of bacterial biofilm. Biofilm
resistance to antimicrobial drugs is now well established as a multicellular approach
that depends essentially on the exchange of chemical signals between the cells.
Quorum sensing quenchers or inhibitors can therefore provide a novel approach by
interfering with bacterial cell-cell communication to prevent the formation of biofilms (Truchado et al. 2015; Algburi et al. 2017).
Several approaches have been developed to interfere with bacterial quorum sensing i.e. (1) competitive binding of inhibitors to the quorum sensing receptors, (2)
inhibition of quorum sensing signals, (3) enzymatic degradation of quorum sensing
signals, and (4) control of quorum sensing genes (Yang and Givskovi 2015). Several
phytocompounds have been explored as quorum sensing inhibitors (QSI); such as
Allium sativum (garlic) crude extracts inhibit the expression of a large number of
quorum sensing controlled genes. Ajoene, a sulfur containing compound found in
garlic extract, has antimicrobial and antibiofilm activity against a number of bacteria, including Escherichia coli, Klebsiella pneumoniae, and Xanthomonas maltophilia (Jakobsen et al. 2012). The efficacy of plant food extracts and phytochemicals
is primarily due to their resemblance to the chemical structure of quorum sensing
signals (Truchado et al. 2015). Quorum sensing inhibitory activity has also identified in Oak bark (Quercus cortex) extract against Chromobacterium violaceum
strain (Deryabin and Tolmacheva 2015). Moreover, eugenol inhibits the production
of quorum sensing mediated violacein in Chromobacterium violaceum and virulence factors in Pseudomonas aeruginosa strains. Eugenol has also found to be
effective against clinical isolates i.e. Listeria monocytogenes and Klebsiella pneumonia (Ta and Arnason 2016). Similarly, methanol extract of Albiza schimperiana
root and petroleum ether extract of Justicia schimperiana seed has also found to
interfere with cell to cell communication of bacterial biofilms (Bacha et al. 2016).
Quercetin, a plant flavonoid, inhibited biofilm formation and quorum sensing regulated characteristics such as violacein inhibition, EPS production and alginate production efficiencies in selected food borne pathogens such as K. pneumoniae,
P. aeruginosa, and Y. enterocolitica (Gopu et al. 2015). Zingerone, a potent antiinflammatory compound found in Zingiber officinale (ginger), also posses potent
effect on quorum sensing signal molecules in clinical isolates of P. aeruginosa
(Kumar et al. 2015) (Table 7.2).
Besides phytocompounds, RNAIII-inhibiting peptide (RIP) has demonstrated
strong activity in preventing methicillin resistant Staphylococcus aureus graft infections in vivo. Actually, Staphylococcus aureus regulates their virulence by using the
B. P. Singh et al.