Lactobacillus plantarum (VR1) isolated from an ayurvedic medicine (Kutajarista) ameliorates in vitro cellular damage caused by Aeromonas veronii

Abstract

Background: Lactobacillus plantarum is considered as a safe and effective probiotic microorganism. Among various sources of isolation, traditionally fermented foods are considered to be rich in Lactobacillus spp., which can be exploited for their probiotic attribute. Antibacterial property of L. plantarum has been demonstrated against various enteric pathogens in both in vitro and in vivo systems. This study was aimed at characterizing L. plantarum isolated from Kutajarista, an ayurvedic fermented biomedicine, and assessing its antagonistic property against a common enteropathogen Aeromonas veronii.

Results: We report the isolation of L. plantarum (VR1) from Kutajarista, and efficacy of its cell free supernatant (CFS) in amelioration of cytotoxicity caused by Aeromonas veronii. On the part of probiotic attributes, VR1 was tolerant to pH 2, 0.3% bile salts and simulated gastric juice. Additionally, VR1 also exhibited adhesive property to human intestinal HT-29 cell line. Furthermore, CFS of VR1 was antibacterial to enteric pathogens like Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Aeromonas veronii and clinical isolates of P. aeruginosa and E. coli. Detailed study regarding the effect of VR1 CFS on A. veronii cytotoxicity showed a significant decrease in vacuole formation and detrimental cellular changes in Vero cells. On the other hand, A. veronii CFS caused disruption of tight junction proteins ZO-1 and actin in MDCK cell line, which was prevented by pre-incubation with CFS of VR1.

Conclusions: This is the first study to report isolation of L. plantarum (VR1) from Kutajarista and characterisation for its probiotic attributes. Our study demonstrates the antagonistic property of VR1 to A. veronii and effect of VR1 CFS in reduction of cellular damage caused by A. veronii in both Vero and MDCK cell lines.

Figure 1

Probiotic properties of VR1. The chart representing the tolerance of VR1 to various physiological conditions of a) pH 2 b) 0.3% bile salts and c) simulated gastric juice, determined at various time points. Data is presented as mean of three independent experiments.

Figure 2

Effect of VR1 culture supernatant on reducing the vacuolation caused by A. veronii. A confluent monolayer of Vero cells treated with culture supernatant, i) control, ii) VR1, iii) A. veronii, iv) VR1 and A. veronii v) A. veronii on Vero cells pre-incubated with VR1 supernatant for 6 h. It is evident that the vacuole formation was decreased when Vero cells were pre-incubated with VR1 supernatant. Arrow indicates vacuolation in Vero cells after treatment with A. veronii culture supernatant.

Figure 3

Effect of VR1 CFS in delaying the cytotoxicity caused by A. veronii. Time lapse microscopic studies were carried out until 10 h incubation of Vero cells with different treatments of culture supernatant of A. veronii and VR1 in 1:10 ratio. We show here the representative images from the treatment of a) control b) A. veronii c) VR1 d) pre-incubation of VR1 for 6 h and then addition of A. veronii e) co-incubation of VR1 and A. veronii. Images a1-a5 represents the incubation time of 2, 4, 6, 8 and 10 h, respectively. Same denomination is followed for other treatments as well. Detachment of Vero cells can be observed from 6 h onwards in A. veronii treated cells. Arrow indicates cell detachment.

Figure 4

Prevention of membrane damage caused due to A. veronii by pre-incubated with CFS of VR1. Epithelial damage observed by immunofluorescence of tight junction proteins ZO-1 and F-actin in MDCK cell line. a) ZO-1 b) Actin c) DAPI d) Merged images for different treatment groups: 1) control, 2) A. veronii 3) VR1 4) co-incubation of VR1 with A. veronii 5) pre-incubation of VR1 with A. veronii. Pre-incubation of VR1 prevents epithelial damage due to A. veronii as observed in the merged image. Scale denotes 20 μm in all images.

Figure 5

Effect of VR1 culture supernatant in preventing the loss of cell viability caused due to A. veronii. MTT assay was performed to quantify percentage cell viability with treatment of supernatant of A. veronii and VR1, in 1:10 ratio. Cell viability graph demonstrates that the pre-incubation with VR1 supernatant for 6 h significantly increased the cell viability. Statistical significance was determined by two tailed student's t-test (n = 3 ± SEM, *p < 0.05).