In vitro evaluation of anti-infective activity of a Lactobacillus plantarum strain against Salmonella enterica serovar Enteritidis

Abstract

BackgroundSalmonella enterica serovar Enteritidis infections are known to exhibit worldwide prevalence with increased morbidity and mortality. The conventional strategies like antibiotic therapy and vaccination have not only proved to be of sub-optimal efficacy but also led to the development of multidrug resistant strains of Salmonella. Antimicrobial activities of probiotics against various enteropathogens and other health promoting effects have assumed greater significance in recent years. The present study aims to evaluate the efficacy of a Lactobacillus plantarum strain (KSBT 56, isolated from a traditional food product of India), in preventing Salmonella enterica serovar Enteritidis growth and pathogenicity in vitro.Methods and resultsThe cell free culture supernatant (CFCS) of KSBT 56 strain notably inhibited the growth of Salmonella Enteritidis without affecting the growth of other gram-positive lactic acid bacteria. The isolated KSBT 56 strain produces lactic acid similar to other standard probiotic strains like Lactobacillus plantarum MTCC 1407. The free radical production by KSBT 56 strain was studied by using sodC mutant of S. Enteritidis, which exhibited reduced growth in the presence of CFCS of the KSBT 56 strain, indicating the inhibitory activity of free radicals on the growth of S. Enteritidis. Our results also showed a significant reduction in the biofilm forming ability of Salmonella Enteritidis in the presence of the KSBT 56 strain (2 log cfu/ml, p = 0.01). Further, the anti-infective characteristics of KSBT 56 strain was validated by gentamicin protection assay which revealed 80% reduction in the invasion of Salmonella Enteritidis to HCT-116 cell line (Salmonella Enteritidis and KSBT 56 in a 1:1 ratio) and delayed addition of Salmonella Enteritidis by 1 h. Similarly, the reduced adhesion of Salmonella to the HCT-116 cells was observed along with the down regulation of hilA gene of Salmonella Pathogenicity Island 1 (SPI1) indicating that they might have acted synergistically to decrease the invasion of the pathogen into the cell line.ConclusionsKSBT 56 strain effectively inhibited the growth, invasion and the biofilm forming ability of Salmonella Enteritidis without inhibiting the growth of other Lactobacillus strains. Overall, our result suggested that KSBT 56 can be used as a potential probiotic strain with considerable beneficial effects on the host.

Characterization and anti-salmonella activities of lactic acid bacteria isolated from cattle faeces

“…The use of antibiotics and vaccination are some of the strategies currently being employed to combat salmonellosis [4]. However, both strategies have shortfalls while vaccination is suboptimal.…”

Correlation between Biofilm Production and Bacterial Urinary Tract Infections: New Therapeutic Approach

“…Probiotics are defined as live microorganisms with health benefit on the host when administered in adequate amounts (Bhan et al, 2005). The use of food based probiotics for nutritional and therapeutic purposes have assumed great significance recently (Das et al, 2013). Lactobacilli gained significant importance in antimicrobial therapy due to their production of different antimicrobial materials such as bacteriocins and biosurfactants (BSs), which affected on formation of biofilms (Gupta & Garg, 2009).…”

The use of Lactic Acid Bacteria to control the growth of foodborne pathogens on fresh-cut fruits and sprout vegetables

“…plantarum is most likely attributed to the production of lactic acid and peroxide radicals (Das et al, 2013). On minimally processed sliced apples, L. plantarum CIT3 strain significantly inhibited E. coli O157:H7.…”

“…The antimicrobial activity of lactic acid bacteria is likely attributed to competition for nutrients and production of organic acids, hydrogen peroxide, antimicrobial enzymes and bacteriocins (Das et al, 2013 Table 3). …”

“…Several Gram-negative and Gram-positive bacteria in the family Enterobacteriaceae and genera Pseudomonas, Lactococcus, Pedioccoccus, and Lactobacillus have been identified as ideal protective bacterial cultures. The identified cultures are known to antagonize foodborne pathogens by several mechanisms, including competition for nutrients and production of organic acids, hydrogen peroxide, antimicrobial enzymes and bacteriocins (Anas et al, 2014;Das et al, 2013;Kumar et al, 2010) Efficacy of protective bacterial cultures in controlling foodborne pathogens on sprout vegetables during sprouting has only recently been explored, with the majority of the research focusing on antagonistic Gram-negative bacteria (Liao et al, 2008;Palmai and Buchanan, 2002;Ye et al, 2010). On mung bean seeds treated with Enterobacter asburiae populations of Salmonella spp.…”