ISSN: 0973-7510

E-ISSN: 2581-690X

Research Article | Open Access
V. Rajeswari1 , Bhuvaneshwari Gunasekar2, Selvakkumar Chinnasamy1 and Merin Mathew3
1Department of Microbiology, Mahe Institute of Dental Sciences and Hospital, Union Territory of Pondicherry, Mahe – 673 310, India.
2Department of Microbiology, Saveetha Medical College, Saveetha University, Chennai – 600 077, Tamil Nadu, India.
3Department of Prosthetic Dental Science- Dental Biomaterials Division, College of Dentistry, Jouf University, Sakaka, Saudi Arabia.
J Pure Appl Microbiol. 2022;16(2):891-900 | Article Number: 7406 | © The Author(s). 2022
Received: 02/11/2021 | Accepted: 28/02/2022 | Published online: 25/04/2022
Issue online: June 2022

Antibiotic resistance is a universal problem in bacterial infections. Hence it gives high priority for new therapeutic methods to alternate conventional antibiotic treatment. Pigment production is one of the virulence characteristics of bacteria regulated by a quorum-sensing mechanism. Antiquorum sensing activities will not directly affect the viability of bacteria; however, they will reduce the pathogenicity of bacteria. Thereby it gives an adverse probability of the development of drug resistance. Aim of our study is to evaluate the activity of (+) usnic acid on pigment production in Pseudomonas aeruginosa MTCC 2453, Chromobacterium violaceum MTCC 2656 and Serratia marcescens MTCC 8708. (+) usnic acid eluted by column chromatography. Dimethyl sulphoxide (DMSO) was used as the solvent for (+) usnic acid. Antibacterial activity determined by Agar well diffusion and broth microdilution methods. Effect on pigment production was assessed by spectroscopy. (+) usnic acid showed accumulative inhibition as its concentration increases on pigment production by Pseudomonas aeruginosa MTCC 2453, Chromobacterium violaceum MTCC 2656 and Serratia marcescens MTCC 8708. The lowest concentrations of (+) usnic acid manifested 50% inhibition of pigment production was 122.67, 87.73 and 205.26 µg/ml respectively on above mentioned order in bacteria. The concentration of (+) usnic acid that showed pigment production inhibition did not hinder the growth of the bacteria, but it can reduce the virulence of the bacteria. This property can be used to resolve the drug resistance in bacteria. Further studies are required to check the action of (+) usnic acid on other virulence factors of the bacteria to prove the quorum quenching activity.


Bio pigments, Chromobacteria, Lichens, Natural compound, Quorum sensing, Quorum quenching

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