Antilisterial Bacteriocin from Lactobacillus rhamnosus CJNU 0519 Presenting a Narrow Antimicrobial Spectrum

Two Recombinant Bacteriocins, Rhamnosin and Lysostaphin, Show Synergistic Anticancer Activity Against Gemcitabine-Resistant Cholangiocarcinoma Cell Lines

Cholangiocarcinoma (CCA), a bile duct cancer with a high mortality rate, has a poor prognosis due to its highly invasive and drug-resistant phenotypes. More effective and selective therapies are urgently needed. Bacteriocins are broad-spectrum antimicrobial peptides/proteins produced by bacterial strains to compete with other bacteria. Recent studies have reported that bacteriocins exhibit anticancer properties against various cancer cell lines with minimal toxicity toward normal cells. In this study, two types of recombinant bacteriocins, rhamnosin from probiotic Lacticaseibacillus rhamnosus and lysostaphin from Staphylococcus simulans, were highly produced in Escherichia coli and subsequently purified via immobilized-Ni2+ affinity chromatography. When their anticancer activity was investigated against CCA cell lines, both rhamnosin and lysostaphin were found capable of inhibiting the growth of CCA cell lines in a dose-dependent fashion but were less toxic toward a normal cholangiocyte cell line. Rhamnosin and lysostaphin as single treatments could suppress the growth of gemcitabine-resistant cell lines to the same extent as or more than they suppressed the parental counterparts. A combination of both bacteriocins more strongly inhibited growth and enhanced cell apoptosis in both parental and gemcitabine-resistant cells partly through the increased expression of the proapoptotic genes BAX, and caspase-3, -8, and -9. In conclusion, this is the first report to demonstrate an anticancer property of rhamnosin and lysostaphin. Using these bacteriocins as single agents or in combination would be effective against drug-resistant CCA.

In-vitro selection of lactic acid bacteria to combat Salmonella enterica and Campylobacter jejuni in broiler chickens

Campylobacter and Salmonella are the two most prominent foodborne zoonotic pathogens reported in the European Union. As poultry is one of the major sources of these pathogens, it is imperative to mitigate the colonization of these pathogens in poultry. Many strains of lactic acid bacteria (LAB) have demonstrated anti-Salmonella and anti-Campylobacter characteristics to varying degrees and spectrums which are attributed to the production of various metabolites. However, the production of these compounds and consequent antimicrobial properties are highly strain dependent. Therefore, the current study was performed to select a potent LAB and determine its causal attribute in inhibiting Salmonella enterica and Campylobacter jejuni, in-vitro. Six LAB (Lactiplantibacillus plantarum (LP), Lacticaseibacillus casei (LC), Limosilactobacillus reuteri (LR), Lacticaseibacillus rhamnosus (LRh), Leuconostoc mesenteroides (LM) and Pediococcus pentosaceus (PP)) and three serovars of Salmonella enterica (Typhimurium, Enterica and Braenderup) and Campylobacter jejuni were used in the current study. Spot overlays, well diffusion, co-culture and co-aggregation assays against Salmonella and well diffusion assays against Campylobacter jejuni were performed. Organic acid profiling of culture supernatants was performed using HPLC. The results indicated that LRh, LM and PP had the most significant anti-Salmonella effects while LP, LC, LM and PP displayed the most significant anti-Campylobacter effects. Lactic acid and formic acid detected in the culture supernatants seem the most likely source of the anti-Salmonella and anti-Campylobacter effects exhibited by these LAB. In conclusion, Leuconostoc mesenteroides displayed the most significant overall anti-pathogenic effects when compared to the other LAB strains studied, indicating its potential application in-vivo.

Purification and characterization of bacteriocin produced by a strain of Lacticaseibacillus rhamnosus ZFM216

The recent surge in demand for natural preservatives has ushered in a new era of research into novel bacteriocins capable of effectively combating food-borne infections. In this study, the bacteriocin from Lacticaseibacillus rhamnosus ZFM216, which has a molecular mass of 11851.9 Da, was purified using macroporous resin, gel chromatography, and reversed-phase high performance liquid chromatography. This bacteriocin could inhibit both Gram-positive and Gram-negative bacteria. It had a strong inhibitory effect on Staphylococcus aureus D48 with minimum inhibitory concentration values of 1.75 μM. Bacteriocin ZFM216 was heat stable and showed pH stability under weakly acidic conditions. It was sensitive to pepsin, proteinase K and trypsin. Electron microscopy results showed that when treated with bacteriocin ZFM216, S. aureus D48 was severely deformed, the cell structure was obviously changed, and the intracellular electrolyte leaked to the outside of the cell. Bacteriocin ZFM216 caused the ATP level of the indicator to decrease, the conductivity to sharply increase, and the transmembrane potential difference (ΔΨ) to instantaneously decrease. This research formed the basis for further development and utilization of bacteriocin ZFM216 which has potential in the food industry.

Complete genome sequences of Lacticaseibacillus paracasei INIA P272 (CECT 8315) and Lacticaseibacillus rhamnosus INIA P344 (CECT 8316) isolated from breast-fed infants reveal probiotic determinants

Lacticaseibacillus paracasei INIA P272 and Lacticaseibacillus rhamnosus INIA P344, isolated from breast-fed infants, are two promising bacterial strains for their use in functional foods according to their demonstrated probiotic and technological characteristics. To better understand their probiotic characteristics and evaluate their safety, here we report the draft genome sequences of both strains as well as the analysis of their genetical content. The draft genomes of L. paracasei INIA P272 and L. rhamnosus INIA P344 comprise 3.01 and 3.26 Mb, a total of 2994 and 3166 genes and a GC content of 46.27 % and 46.56 %, respectively. Genomic safety was assessed following the EFSA guidelines: the identification of both strains was confirmed through Average Nucleotide Identity, and the absence of virulence, pathogenic and antibiotic resistance genes was demonstrated. The genome stability analysis revealed the presence of plasmids and phage regions in both genomes, however, CRISPR sequences and other mechanisms to fight against phage infections were encoded. The probiotic abilities of both strains were supported by the presence of genes for the synthesis of SCFA, genes involved in resistance to acid and bile salts or a thiamine production cluster. Moreover, the encoded exopolysaccharide biosynthesis genes could provide additional protection against the deleterious gastrointestinal conditions, besides which, playing a key role in adherence and coaggregation of pathogenic bacteria together with the high number of adhesion proteins and domains encoded by both genomes. Additionally, the bacteriocin cluster genes found in both strains, could provide an advantageous ability to compete against pathogenic bacteria. This genomic study supports the probiotic characteristics described previously for these two strains and satisfies the safety requirements to be used in food products.

Targeted Antimicrobial Agents as Potential Tools for Modulating the Gut Microbiome

The gut microbiome plays a pivotal role in maintaining the health of the hosts; however, there is accumulating evidence that certain bacteria in the host, termed pathobionts, play roles in the progression of diseases. Although antibiotics can be used to eradicate unwanted bacteria, the side effects of antibiotic treatment lead to a great need for more targeted antimicrobial agents as tools to modulate the microbiome more precisely. Herein, we reviewed narrow-spectrum antibiotics naturally made by plants and microorganisms, followed by more targeted antibiotic agents including synthetic peptides, phage, and targeted drug delivery systems, from the perspective of using them as potential tools for modulating the gut microbiome for favorable effects on the health of the host. Given the emerging discoveries on pathobionts and the increasing knowledge on targeted antimicrobial agents reviewed in this article, we anticipate targeted antimicrobial agents will emerge as a new generation of a drug to treat microbiome-involved diseases.

Lacticaseibacillus rhamnosus: A Suitable Candidate for the Construction of Novel Bioengineered Probiotic Strains for Targeted Pathogen Control

Probiotics, with their associated beneficial effects, have gained popularity for the control of foodborne pathogens. Various sources are explored with the intent to isolate novel robust probiotic strains with a broad range of health benefits due to, among other mechanisms, the production of an array of antimicrobial compounds. One of the shortcomings of these wild-type probiotics is their non-specificity. A pursuit to circumvent this limitation led to the advent of the field of pathobiotechnology. In this discipline, specific pathogen gene(s) are cloned and expressed into a given probiotic to yield a novel pathogen-specific strain. The resultant recombinant probiotic strain will exhibit enhanced species-specific inhibition of the pathogen and its associated infection. Such probiotics are also used as vehicles to deliver therapeutic agents. As fascinating as this approach is, coupled with the availability of numerous probiotics, it brings a challenge with regard to deciding which of the probiotics to use. Nonetheless, it is indisputable that an ideal candidate must fulfil the probiotic selection criteria. This review aims to show how Lacticaseibacillus rhamnosus, a clinically best-studied probiotic, presents as such a candidate. The objective is to spark researchers’ interest to conduct further probiotic-engineering studies using L. rhamnosus, with prospects for the successful development of novel probiotic strains with enhanced beneficial attributes.

Interactions between probiotic and oral pathogenic strains

More than 6 billion bacteria and other microorganisms live in the adult oral cavity. As a result of any deleterious effect on this community, some microorganisms will survive better than others, which may trigger pathogenic processes like caries, halitosis, gingivitis or periodontitis. Oral dysbiosis is among the most frequent human health hazards globally. Quality of life of patients deteriorates notably, while treatments are often unpleasant, expensive and irreversible, e.g. tooth loss. In the experiments reported here, we investigated the individual interactions between 8 pathogenic and 8 probiotic strains and a commercially available probiotic product. Almost all pathogens, namely Fusobacterium nucleatum, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Streptococcus mutans, Streptococcus oralis, Streptococcus gordonii, Enterococcus faecalis and Prevotella buccae are pathogens frequently occurring in the oral cavity. The used probiotic strains were Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus delbrueckii, Bifidobacterium thermophilum and two Streptococcus dentisani isolates. Using a modified agar diffusion method, we investigated capability of the probiotic bacteria to prevent the growth of the pathogenic ones in order to identify candidates for future therapeutic treatments. The results indicated successful bacteriocin production, i.e. growth inhibition, against every pathogenic bacterium by at least 5 probiotic strains.

Lacticaseibacillus rhamnosus Impedes Growth of Listeria spp. in Cottage Cheese through Manganese Limitation

Acidification and nutrient depletion by dairy starter cultures is often sufficient to prevent outgrowth of pathogens during post-processing of cultured dairy products. In the case of cottage cheese, however, the addition of cream dressing to the curd and subsequent cooling procedures can create environments that may be hospitable for the growth of Listeria monocytogenes. We report on a non-bacterio-cinogenic Lacticaseibacillus rhamnosus strain that severely limits the growth potential of L. monocytogenes in creamed cottage cheese. The main mechanism underlying Listeria spp. inhibition was found to be caused by depletion of manganese (Mn), thus through competitive exclusion of a trace element essential for the growth of many microorganisms. Growth of Streptococcus thermophilus and Lactococcus lactis that constitute the starter culture, on the other hand, were not influenced by reduced Mn levels. Addition of L. rhamnosus with Mn-based bioprotective properties during cottage cheese production therefore offers a solution to inhibit undesired bacteria in a bacteriocin-independent fashion.

Bacteriocins, A Natural Weapon Against Bacterial Contamination for Greater Safety and Preservation of Food: A Review

Nowadays, consumers have become increasingly attentive to human health and the use of more natural products. Consequently, the demand for natural preservatives in the food industry is more frequent. This has led to intense research to discover new antimicrobial compounds of natural origin that could effectively fight foodborne pathogens. This research aims to safeguard the health of consumers and, above all, to avoid potentially harmful chemical compounds. Lactobacillus is a bacterial genus belonging to the Lactic Acid Bacteria and many strains are defined GRAS, generally recognized as safe. These strains are able to produce substances with antibacterial activity against food spoilage bacteria and contaminating pathogens: the bacteriocins. The aim of this review was to focus on this genus and its capability to produce antibacterial peptides. The review collected all the information from the last few years about bacteriocins produced by Lactobacillus strains, isolated from clinical or food samples, with remarkable antimicrobial activities useful for being exploited in the food field. In addition, the advantages and disadvantages of their use and the possible ways of improvement for industrial applications were described.

Antilisterial Potential of Lactic Acid Bacteria in Eliminating Listeria monocytogenes in Host and Ready-to-Eat Food Application

Listeriosis is a severe food borne disease with a mortality rate of up to 30% caused by pathogenic Listeria monocytogenes via the production of several virulence factors including listeriolysin O (LLO), transcriptional activator (PrfA), actin (Act), internalin (Int), etc. It is a foodborne disease predominantly causing infections through consumption of contaminated food and is often associated with ready-to-eat food (RTE) and dairy products. Common medication for listeriosis such as antibiotics might cause an eagle effect and antibiotic resistance if it is overused. Therefore, exploration of the use of lactic acid bacteria (LAB) with probiotic characteristics and multiple antimicrobial properties is increasingly getting attention for their capability to treat listeriosis, vaccine development, and hurdle technologies. The antilisterial gene, a gene coding to produce antimicrobial peptide (AMP), one of the inhibitory substances found in LAB, is one of the potential key factors in listeriosis treatment, coupled with the vast array of functions and strategies; this review summarizes the various strategies by LAB against L. monocytogenes and the prospect in development of a ‘generally regarded as safe’ LAB for treatment of listeriosis.

Biological properties and production of bacteriocins-like-inhibitory substances by Lactobacillus sp. strains from human vagina

AIMS

The aim of this study was to characterize Lactobacillus strains for their biological properties and amensalistic activities against genital and nongenital pathogens.

METHODS AND RESULTS

For the purpose, some special characteristics (H₂ O₂ , biofilm and antimicrobial substances production) as well as safety properties of 112 lactobacilli were evaluated. All the strains had good amensalistic characteristics, in particular cell-free supernatants of 10 strains showed antibacterial activity against bacteria, as well as Candida sp. Moreover, these 10 strains were excellent biofilm producers.

CONCLUSIONS

These results provide evidence for the possible use as probiotics for vaginal co-therapy in case of dysbiosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Recently, the problem of antibiotic resistance is constantly increasing, even though resources and energy are invested in order to increase knowledge on the mechanisms of action. Bacteriocins have a rapid mechanism of action, act at extremely low concentrations, are generally sensitive to proteases and they usually have a narrow killing spectrum; these characteristics reduce the possibility of the bacterium to develop resistance. This study is focused on the feasibility of a high production of antimicrobial substances and their characterization in order to be exploited as a therapeutic alterative or in co-therapy with antibiotics in case of vaginal dysbiosis.

Novel Biocontrol Methods for Listeria monocytogenes Biofilms in Food Production Facilities

High mortality and hospitalization rates have seen Listeria monocytogenes as a foodborne pathogen of public health importance for many years and of particular concern for high-risk population groups. Food manufactures face an ongoing challenge in preventing the entry of L. monocytogenes into food production environments (FPEs) due to its ubiquitous nature. In addition to this, the capacity of L. monocytogenes strains to colonize FPEs can lead to repeated identification of L. monocytogenes in FPE surveillance. The contamination of food products requiring product recall presents large economic burden to industry and is further exacerbated by damage to the brand. Poor equipment design, facility layout, and worn or damaged equipment can result in Listeria hotspots and biofilms where traditional cleaning and disinfecting procedures may be inadequate. Novel biocontrol methods may offer FPEs effective means to help improve control of L. monocytogenes and decrease cross contamination of food. Bacteriophages have been used as a medical treatment for many years for their ability to infect and lyse specific bacteria. Endolysins, the hydrolytic enzymes of bacteriophages responsible for breaking the cell wall of Gram-positive bacteria, are being explored as a biocontrol method for food preservation and in nanotechnology and medical applications. Antibacterial proteins known as bacteriocins have been used as alternatives to antibiotics for biopreservation and food product shelf life extension. Essential oils are natural antimicrobials formed by plants and have been used as food additives and preservatives for many years and more recently as a method to prevent food spoilage by microorganisms. Competitive exclusion occurs naturally among bacteria in the environment. However, intentionally selecting and applying bacteria to effect competitive exclusion of food borne pathogens has potential as a biocontrol application. This review discusses these novel biocontrol methods and their use in food safety and prevention of spoilage, and examines their potential to control L. monocytogenes within biofilms in food production facilities.

In silico Prediction, in vitro Antibacterial Spectrum, and Physicochemical Properties of a Putative Bacteriocin Produced by Lactobacillus rhamnosus Strain L156.4

A bacteriocinogenic Lactobacillus rhamnosus L156.4 strain isolated from the feces of NIH mice was identified by 16S rRNA gene sequencing and MALDI-TOF mass spectrometry. The entire genome was sequenced using Illumina, annotated in the PGAAP, and RAST servers, and deposited. Conserved genes associated with bacteriocin synthesis were predicted using BAGEL3, leading to the identification of an open reading frame (ORF) that shows homology with the L. rhamnosus GG (ATCC 53103) prebacteriocin gene. The encoded protein contains a conserved protein motif associated a structural gene of the Enterocin A superfamily. We found ORFs related to the prebacteriocin, immunity protein, ABC transporter proteins, and regulatory genes with 100% identity to those of L. rhamnosus HN001. In this study, we provide evidence of a putative bacteriocin produced by L. rhamnosus L156.4 that was further confirmed by in vitro assays. The antibacterial activity of the substances produced by this strain was evaluated using the deferred agar-spot and spot-on-the lawn assays, and a wide antimicrobial activity spectrum against human and foodborne pathogens was observed. The physicochemical characterization of the putative bacteriocin indicated that it was sensitive to proteolytic enzymes, heat stable and maintained its antibacterial activity in a pH ranging from 3 to 9. The activity against Lactobacillus fermentum, which was used as an indicator strain, was detected during bacterial logarithmic growth phase, and a positive correlation was confirmed between bacterial growth and production of the putative bacteriocin. After a partial purification from cell-free supernatant by salt precipitation, the putative bacteriocin migrated as a diffuse band of approximately 1.0-3.0 kDa by SDS-PAGE. Additional studies are being conducted to explore its use in the food industry for controlling bacterial growth and for probiotic applications.