Antagonistic Activity of Bacteriocins Produced by Lactobacillus Isolates against Multidrug Resistant Pathogens

Background: Multi drug-resistance pose a great threat to public health and are responsible for various life-threatening ailments. There is a crucial need to control the outbreaks by finding alternatives to the conventional drugs available. Over the last few years, the usage of probiotics, including Lactobacillus spp. and their bacteriocins has gained much attention to ward off various diseases.

Methods: This study was focused on characterizing bacteriocins extracted from Lactobacillus spp. and assessing their antagonistic effect against multi-drug resistant bacteria. Fifteen Lactobacillus spp. were isolated and identified from Pakistani dairy and fermented products (raw milk, cheese, butter milk, pickle and yoghurt). All the isolates were preliminarily screened by the antagonism method of agar well diffusion method, and the bacteriocins were isolated by ammonium sulphate method. Afterwards, to evaluate the release of bacteriocin in liquid medium, the Cell-Free Supernatant Fluid (CFSF) of the best producer strains were tested by agar well diffusion assay. To assess the thermostability of the bacteriocins, they were subjected to temperatures of 40ᴼC, 60ᴼC, 80ᴼC and 100ᴼC.

Results: The study allowed the selection of five bacteriocin producing strains Lactobacillus acidophilus KAL1, Lactobacillus casei KAL3, Lactobacillus plantarum KAL5, Lactobacillus reuteri KAL6 and Lactobacillus spp. delbrukei KAL7, endowed with the strongest and broadest inhibitory ability against both Gram-positive (Methicillin Resistant Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria. Bacteriocins isolated were significantly thermostable with activity at 80ᴼC (30, 20 min) respectively. Moreover, all the bacteriocins were considerably stable at a range of pH (4–8) but all the activity was eliminated against proteolytic enzyme Proteinase K.

Conclusion: From this study, it was concluded that bacteriocin extracts from five isolated Lactobacillus spp. can be considered a preferable candidate against multi-drug resistant pathogens. These partially purified bacteriocins should be further processed to attain purified product that could be useful for further studies for the control of pathogens, food spoilage and preservation purposes.