Anti-quorum sensing and anti-biofilm activity of Amomum tsaoko (Amommum tsao-ko Crevost et Lemarie) on foodborne pathogens

Abstract

Cell-to-cell communication or quorum sensing (QS) leads to biofilm formation and causing other virulence factors which are extreme problems for food safety, biofilm related infectious diseases etc. This study evaluated the anti-QS activity of the Amomum tsaoko extract (0.5-4 mg/ml) by using Chromobacterium violaceum a biosensor strain and biofilm formation by crystal violate assay. Experimental results demonstrated that the overall yield of Amomum tsao-ko extract was 11.33 ± 0.3% (w/w). MIC for Staphylococcus aureus (Gram positive), Salmonella Typhimurium and Pseudomonas aeruginosa (Gram negative) was 1, 2 and 2 mg/ml, respectively. A concentration of 4 mg/ml extract showed highest biofilm inhibition 51.96% on S. Typhimurium when 47.06%, 45.28% were shown by S. aureus, P. aeruginosa respectively. The damage of biofilm architecture was observed by Confocal Laser Scanning Microscopy (CLSM). A level of 44.59% inhibition of violacein production was demonstrated when the dose was 4 mg/ml. Swarming motility inhibition was observed in a dose dependent manner. Taken together, the treatment of A. tsaoko extract can deliver value to food product and medicine by controlling pathogenesis.

Keywords: Amomum tsaoko; Biofilm; Drug; Food spoilage; Quorum sensing.

Figure 1

Anti-quorum sensing (anti-QS) activity by Amomum tsaoko extract against bioreporter strain CV12472, using agar disk diffusion method. Amomum tsaoko extract (4 mg/ml) and positive control (vanillin, 250 μg/ml) loaded disk are showing colorless, opaque circle. While, negative control (LB broth loaded disk) is showing no inhibition of violacein production around the disk.

Figure 2

Effect of A. tsaoko extract on violacein production. Data are represented as percentage of violacein inhibition. Control (untreated) was set as 100% production. Mean values of triplicate independent experiments and SD are shown. Not significantly different at P ⩽ 0.05 of treatment.

Figure 3

Observation of biofilm on CLSM. (a–c) Untreated biofilm of Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella Typhimurium (ta-tc) treated biofilm of Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella Typhimurium respectively.

Figure 4

The migration distance of Staphylococcus aureus, Salmonella Typhimurium, Pseudomonas aeruginosa was observed while they were incubated for 30 h at different concentrations of A. tsaoko extract. Swarming motility of (a) Pseudomonas aeruginosa (b) Salmonella Typhimurium (c) Staphylococcus aureus in the presence of Amomum tsaoko extracts (left–right; 0.5, 1, 2, 4 mg/ml, control : without extract).