Bacterial drug resistance is a challenge in clinical settings, especially in countries like India. Hence, discovery of novel alternative therapeutics has become a necessity in the fight against drug resistance. Compounds that inhibit bacterial virulence properties form new therapeutic alternatives. Pseudomonas aeruginosa is an opportunistic, nosocomial pathogen that infects immune-compromised patients. Swarming motility is an important virulence property of Pseudomonas which aids it in reaching host cells under nutrient limiting conditions. Here, we report the screening of five plant extracts against swarming motility of P. aeruginosa and show that methanol extracts of Alpinia officinarum and Cinnamomum tamala inhibit swarming motility at 5 μg mL without inhibiting its growth. These extracts did not inhibit swimming and twitching motilities indicating a mode of action specific to swarming pathway. Preliminary experiments indicated that rhamnolipid production was not affected. This study reveals the potential of the two plants in anti-virulence drug discovery.
Aim:The study was aimed at purifying the active principle from Alpinia officinarum rhizomes responsible for inhibition of swarming motility of Pseudomonas aeruginosa and analysing the mechanism of action. Methods and Results: The active compound from methanol extract of A. officinarum was purified by silica gel column chromatography followed by elution from Amberlite resin. The compound 1-(3,5-dihydroxyphenyl)-2-(methylamino)ethan-1-one, inhibited swarming motility at 12Á5 µg ml À1 . This inhibition was independent of rhamnolipid production. Real-time PCR analysis showed significant down-regulation of virulence-associated genes including T3SS exoS, exoT and flagella master regulator fleQ. Conclusions: The compound from A. officinarum inhibited swarming motility and significantly down-regulated the expression of type III secretory system effector genes exoS and exoT and flagellar master regulator fleQ genes. Significance and Impact of the Study: The study identifies a potent swarming inhibitory compound from the common medicinal plant A. officinarum and reinstates the potential of plant-derived compounds in tackling virulence properties of pathogenic bacteria. et al. 2007) and type III secretory system (T3SS) (Overhage et al. 2008) among others. In addition, swarming cells are also reported to show increased tolerance to antibiotics (Overhage et al. 2008; Lai et al. 2009). Swarming motility was found to be positively associated with clinical features of ocular keratitis (Oka et al. 2015). Although many genes have been identified that regulate swarming motility, it is a complex behaviour involving a network of several genes and pathways including quorum
In
a preliminary screening, the methanol extract of Cinnamomum
tamala leaves was found to inhibit the
swarming motility of Pseudomonas aeruginosa. Bioassay-guided fractionation by silica gel column chromatography
led to the identification of cinnamtannin B1 (1) as one
of the active components of the extract. It inhibited the swarming
motility (at 12.5 μg/mL) and biofilm formation (at 25 μg/mL)
ofP. aeruginosa. Comparative gene expression
analysis revealed downregulation of rhlA and fliC genes upon treatment with the tannin. The tannin may
be affecting rhamnolipid and flagellin production. Thus, cinnamtannin
B1 is an active component of C. tamala responsible for inhibiting the swarming motility of P. aeruginosa.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.