Antibacterial effects of Lactobacillus isolates of curd and human milk origin against food-borne and human pathogens

Abstract

This study was undertaken to assess the antibacterial efficacy of lactobacilli isolated from curd and human milk samples. Identities of thirty-one different lactobacilli (20 from curd and 11 from human milk) were confirmed by genus-specific PCR and 16S rRNA-based sequencing. These strains belonged to five species, Lactobacillus casei, L. delbrueckii, L. fermentum, L. plantarum, and L. pentosus. Antibacterial activities of cell-free supernatants (CFSs) of all the Lactobacillus isolates were estimated through standard agar-well diffusion assay, against commonly occurring food-borne and clinically important human pathogens. None of the lactobacilli cell-free supernatant (CFS) exhibited inhibitory activity against four pathogens, namely Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Klebsiella pneumoniae. Bacillus cereus, Salmonella enterica serovar Typhi, and Shigella flexneri were moderately inhibited by majority of CFSs, whereas, weak activity was observed against Pseudomonas aeruginosa and Proteus mirabilis. CFS of some of the curd isolates displayed antagonistic activity against Streptococcus mutans; however, human milk lactobacilli did not displayed any inhibitory activity against them. As expected, Nisin (Nisaplin®) showed inhibitory activity against Gram-positive, S. aureus, B. cereus, and L. monocytogenes. Interestingly, few of the examined CFSs exhibited inhibitory activities against both Gram-positive and Gram-negative pathogens. Findings from this study support the possibility to explore the tested lactobacilli and their CFSs as natural bio-preservatives, alone or in combination with approved bacteriocins in food and pharma formulations after validating their safety.

Antibiotic sensitivity pattern of indigenous lactobacilli isolated from curd and human milk samples

“…However, it is also important that the resistance should be inherent and non-transferrable. Natural antimicrobial properties of LABs may further pose a synergistic effect to antibiotic therapy in eliminating pathogenic strains (Sharma et al 2017). Further, synergistic application of different antibiotics groups may display strong activity against resistant strains and may prevent build-up of strong resistance in strains currently showing intermediate susceptibility.…”

Antimicrobial activity ofLactobacillus rhamnosusagainstPseudomonas fluorescensandPseudomonas putidafrom raw milk

“…Lactobacillus spp. produce a wide variety of antimicrobial compounds such as organic acids (lactic acid, acetic acid, and propionic acid), peroxides, bacteriocins, and antimicrobial peptides (De Vuyst & Leroy, ; Jamuna & Jeevaratnam, ; Sharma et al, ). Lactobacilli may produce acids through the heterofermentative pathway, which promotes the antibacterial effect probably via physiological and morphological changes in the bacterial cytoplasmic membrane, resulting in the leakage of the cytoplasmic content (Wang et al, ).…”

In vitro Assessment of Antibiotic Resistance Pattern among Lactobacillus Strains Isolated from Goat Milk

“…However, such resistance should be intrinsic and non-transferable; as intrinsic resistance and resistance due to mutation of chromosomal genes present a low risk of horizontal dissemination. Further, antimicrobial potential of LAB further enhances the efficacy of antimicrobial drug therapy, as it also helps in eradicating the pathogenic microorganism (Sharma et al, 2017b). In the current study, we have observed a wide range of resistance among goat Lactobacillus isolates; therefore further studies are needed to understand the resistance mechanisms on molecular basis.…”

“…from raw goat (Beetal) milk obtained from dairy farm of Guru Angad Dev Veterinary and Animal Sciences University (GADVASU) Ludhiana, Punjab, India. Milk samples were processed and lactobacilli were isolated and identified as discussed previously (Panwar et al, 2016;Sharma et al, 2017a and2017b …”