Antibacterial activities of bacteriocins: application in foods and pharmaceuticals

Bacteriocins: An Overview of Antimicrobial, Toxicity, and Biosafety Assessment by in vivo Models

The world is facing a significant increase in infections caused by drug-resistant infectious agents. In response, various strategies have been recently explored to treat them, including the development of bacteriocins. Bacteriocins are a group of antimicrobial peptides produced by bacteria, capable of controlling clinically relevant susceptible and drug-resistant bacteria. Bacteriocins have been studied to be able to modify and improve their physicochemical properties, pharmacological effects, and biosafety. This manuscript focuses on the research being developed on the biosafety of bacteriocins, which is a topic that has not been addressed extensively in previous reviews. This work discusses the studies that have tested the effect of bacteriocins against pathogens and assess their toxicity using in vivo models, including murine and other alternative animal models. Thus, this work concludes the urgency to increase and advance the in vivo models that both assess the efficacy of bacteriocins as antimicrobial agents and evaluate possible toxicity and side effects, which are key factors to determine their success as potential therapeutic agents in the fight against infections caused by multidrug-resistant microorganisms.

Marine Microbial-Derived Antibiotics and Biosurfactants as Potential New Agents against Catheter-Associated Urinary Tract Infections

Catheter-associated urinary tract infections (CAUTIs) are among the leading nosocomial infections in the world and have led to the extensive study of various strategies to prevent infection. However, despite an abundance of anti-infection materials having been studied over the last forty-five years, only a few types have come into clinical use, providing an insignificant reduction in CAUTIs. In recent decades, marine resources have emerged as an unexplored area of opportunity offering huge potential in discovering novel bioactive materials to combat human diseases. Some of these materials, such as antimicrobial compounds and biosurfactants synthesized by marine microorganisms, exhibit potent antimicrobial, antiadhesive and antibiofilm activity against a broad spectrum of uropathogens (including multidrug-resistant pathogens) that could be potentially used in urinary catheters to eradicate CAUTIs. This paper summarizes information on the most relevant materials that have been obtained from marine-derived microorganisms over the last decade and discusses their potential as new agents against CAUTIs, providing a prospective proposal for researchers.

Bacteriocins from Lactic Acid Bacteria. A Powerful Alternative as Antimicrobials, Probiotics, and Immunomodulators in Veterinary Medicine

In the search for an alternative treatment to reduce antimicrobial resistance, bacteriocins shine a light on reducing this problem in public and animal health. Bacteriocins are peptides synthesized by bacteria that can inhibit the growth of other bacteria and fungi, parasites, and viruses. Lactic acid bacteria (LAB) are a group of bacteria that produce bacteriocins; their mechanism of action can replace antibiotics and prevent bacterial resistance. In veterinary medicine, LAB and bacteriocins have been used as antimicrobials and probiotics. However, another critical role of bacteriocins is their immunomodulatory effect. This review shows the advances in applying bacteriocins in animal production and veterinary medicine, highlighting their biological roles.

Building blocks and blueprints for bacterial autolysins

Bacteria utilize a wide variety of endogenous cell wall hydrolases, or autolysins, to remodel their cell walls during processes including cell division, biofilm formation, and programmed death. We here systematically investigate the composition of these enzymes in order to gain insights into their associated biological processes, potential ways to disrupt them via chemotherapeutics, and strategies by which they might be leveraged as recombinant antibacterial biotherapies. To do so, we developed LEDGOs (lytic enzyme domains grouped by organism), a pipeline to create and analyze databases of autolytic enzyme sequences, constituent domain annotations, and architectural patterns of multi-domain enzymes that integrate peptidoglycan binding and degrading functions. We applied LEDGOs to eight pathogenic bacteria, gram negatives Acinetobacter baumannii, Klebsiella pneumoniae, Neisseria gonorrhoeae, and Pseudomonas aeruginosa; and gram positives Clostridioides difficile, Enterococcus faecium, Staphylococcus aureus, and Streptococcus pneumoniae. Our analysis of the autolytic enzyme repertoires of these pathogens reveals commonalities and differences in their key domain building blocks and architectures, including correlations and preferred orders among domains in multi-domain enzymes, repetitions of homologous binding domains with potentially complementarity recognition modalities, and sequence similarity patterns indicative of potential divergence of functional specificity among related domains. We have further identified a variety of unannotated sequence regions within the lytic enzymes that may themselves contain new domains with important functions.

Bovine mastitis prevention and control in the post-antibiotic era

Mastitis is the most important disease in the dairy industry. Antibiotics are considered to be the first choice in the treatment of the disease. However, the problem of antibiotic residue and antimicrobial resistance, in addition to the impact of antibiotic abuse on public health, leads to many restrictions on uncontrolled antibiotic therapy in the dairy sector worldwide. Researchers have investigated novel therapeutic approaches to replace the use of antibiotics in mastitis control. These efforts, supported by the revolutionary development of nanotechnology, stem cell assays, molecular biological tools, and genomics, enabled the development of new approaches for mastitis-treatment and control. The present review discusses recent concepts to control mastitis such as breeding of mastitis-resistant dairy cows, the development of novel diagnostic and therapeutic tools, the application of communication technology as an educational and epidemiological tool, application of modern mastitis vaccines, cow drying protocols, teat disinfection, housing, and nutrition. These include the application of nanotechnology, stem cell technology, photodynamic and laser therapy or the use of traditional herbal medical plants, nutraceuticals, antibacterial peptides, bacteriocins, antibodies therapy, bacteriophages, phage lysins, and probiotics as alternatives to antibiotics.

Oral probiotic activities and biosafety of Lactobacillus gasseri HHuMIN D

Background

Lactobacillus spp. have been researched worldwide and are used in probiotics, but due to difficulties with laboratory cultivation of and experimentation on oral microorganisms, there are few reports of Lactobacillus spp. being isolated from the oral cavity and tested against oral pathogens. This research sought to isolate and determine the safety and inhibitory capabilities of a Lactobacillus culture taken from the human body.

Results

One organism was isolated, named “L. gasseri HHuMIN D”, and evaluated for safety. A 5% dilution of L. gasseri HHuMIN D culture supernatant exhibited 88.8% inhibition against halitosis-producing anaerobic microorganisms and the organism itself exhibited powerful inhibitory effects on the growth of 11 oral bacteria. Hydrogen peroxide production reached 802 μmol/L after 12 h and gradually diminished until 24 h, it efficiently aggregated with P. catoniae and S. sanguinis, and it completely suppressed S. mutans-manufactured artificial dental plaque. L. gasseri HHuMIN D’s KB cell adhesion capacity was 4.41 cells per cell, and the cell adhesion of F. nucleatum and S. mutans diminished strongly in protection and displacement assays.

Conclusion

These results suggest that L. gasseri HHuMIN D is a safe, bioactive, lactobacterial food ingredient, starter culture, and/or probiotic microorganism for human oral health.

Green synthesis of colloidal selenium nanoparticles in starch solutions and investigation of their photocatalytic, antimicrobial, and cytotoxicity effects

In this research, we have offered a green and new synthesizing procedure for selenium nanoparticles (Se-NPs) through the utilization of Na₂SeO₃, in which starch has a role of stabilizer and capping agent, as the functionality of green reducing mediums is taken by glucose and ascorbic acid. According to the observations, this method has been capable of producing Se-NPs in lab conditions. Additionally, the synthesized Se-NPs can be separated from the aqueous solution of stabilizer and reducing agents by a high-speed. Certain analyzing procedures have been used to characterize the obtained particles including TEM, XRD, UV-VIS, DLS, FESEM, EDX, FTIR, and AFM. In this paper, we have investigated the antimicrobial and photocatalytic functionality of Se-NPs on Mycobacterium tuberculosis and Methylene blue (MB) and according to the results, these particles have shown satisfying activity in both cases. To be stated in exact, about 60% of MB has degraded under UV light after 150 min, which indicates the acceptable position of Se-NPs could be applied for eliminating water pollutions. Moreover, the attained data on colorectal cancer SW480 cell lines in regards to the in vitro cytotoxicity assessments have exhibited non-toxic effects, which had lasted throughout concentrations that had measured up to even 100 µg/mL within MTT assay.

An antimicrobial Staphylococcus sciuri with broad temperature and salt spectrum isolated from the surface of the African social spider, Stegodyphus dumicola

Some social arthropods engage in mutualistic symbiosis with antimicrobial compound-producing microorganisms that provide protection against pathogens. Social spiders live in communal nests and contain specific endosymbionts with unknown function. Bacteria are also found on the spiders' surface, including prevalent staphylococci, which may have protective potential. Here we present the genomic and phenotypic characterization of strain i1, isolated from the surface of the social spider Stegodyphus dumicola. Phylogenomic analysis identified i1 as novel strain of Staphylococcus sciuri within subgroup 2 of three newly defined genomic subgroups. Further phenotypic investigations showed that S. sciuri i1 is an extremophile that can grow at a broad range of temperatures (4 °C-45 °C), high salt concentrations (up to 27%), and has antimicrobial activity against closely related species. We identified a lactococcin 972-like bacteriocin gene cluster, likely responsible for the antimicrobial activity, and found it conserved in two of the three subgroups of S. sciuri. These features indicate that S. sciuri i1, though not a specific symbiont, is well-adapted to survive on the surface of social spiders and may gain a competitive advantage by inhibiting closely related species.

Anticancer and antimicrobial potential of enterocin 12a from Enterococcus faecium

BACKGROUND

Increase in the number of infections caused by Gram-negative bacteria in neutropenic cancer patients has prompted the search for novel therapeutic agents having dual anticancer and antimicrobial properties. Bacteriocins are cationic proteins of prokaryotic origin that have emerged as one of the most promising alternative antimicrobial agents with applications as food preservatives and therapeutic agents. Apart from their antimicrobial activities, bacteriocins are also being explored for their anticancer potential.

RESULTS

In this study, a broad-spectrum, cell membrane-permeabilizing enterocin with a molecular weight of 65 kDa was purified and characterized from the culture supernatant of vaginal Enterococcus faecium 12a. Enterocin 12a inhibited multidrug-resistant strains of various Gram-negative pathogens such as Salmonella enterica, Shigella flexneri, Vibrio cholerae, Escherichia coli and Gram-positive, Listeria monocytogenes, but had no activities against different strains of gut lactobacilli. The mass spectrometric analysis showed that the enterocin 12a shared partial homology with 4Fe-4S domain-containing redox protein of E. faecalis R712. Further, enterocin 12a selectively inhibited the proliferation of various human cancer cell lines in a dose-dependent manner but not that of normal human peripheral blood mononuclear cells. Enterocin 12a-treated cancer cells showed apoptosis-like morphological changes.

CONCLUSION

Enterocin 12a is a novel bacteriocin that has anticancer properties against human cell lines and negligible activity towards non-malignant cells. Therefore, it should be further evaluated for its anticancer potential in animal models.

Virulence Factors in Coagulase-Negative Staphylococci

Coagulase-negative staphylococci (CoNS) have emerged as major pathogens in healthcare-associated facilities, being S. epidermidis, S. haemolyticus and, more recently, S. lugdunensis, the most clinically relevant species. Despite being less virulent than the well-studied pathogen S. aureus, the number of CoNS strains sequenced is constantly increasing and, with that, the number of virulence factors identified in those strains. In this regard, biofilm formation is considered the most important. Besides virulence factors, the presence of several antibiotic-resistance genes identified in CoNS is worrisome and makes treatment very challenging. In this review, we analyzed the different aspects involved in CoNS virulence and their impact on health and food.

Microbial biopreservatives for controlling the spoilage of beef and lamb meat: their application and effects on meat quality

Biopreservation is a recognized natural method for controlling the growth of undesirable bacteria on fresh meat. It offers the potential to inhibit spoilage bacteria and extend meat shelf-life, but this aspect has been much less studied compared to using the approach to target pathogenic bacteria. This review provides comprehensive information on the application of biopreservatives of microbial origin, mainly bacteriocins and protective cultures, in relation to bacterial spoilage of beef and lamb meat. The sensory effect of these biopreservatives, an aspect that often receives less attention in microbiological studies, is also reviewed. Microbial biopreservatives were found to be able to retard the growth of the major meat spoilage bacteria, Brochothrix thermosphacta, Pseudomonas spp., and Enterobacteriaceae. Their addition did not have any discernible negative impact on the sensory properties of meat, whether assessed by human sensory panels or instrumental and chemical analyses. Although results are promising, the concept of biopreservation for controlling spoilage bacteria on fresh meat is still in its infancy. Studies in this area are still lacking, especially for lamb. Biopreservatives need more testing under conditions representative of commercial meat production, along with studies of any possible sensory effects, in order to validate their potential for large-scale industrial applications.

Potential Novel Food-Related and Biomedical Applications of Nanomaterials Combined with Bacteriocins

Bacteriocins are antimicrobial peptides or proteinaceous materials produced by bacteria against pathogens. These molecules have high efficiency and specificity and are equipped with many properties useful in food-related applications, such as food preservatives and additives, as well as biomedical applications, such as serving as alternatives to current antibacterial, antiviral, anticancer, and antibiofilm agents. Despite their advantages as alternative therapeutics over existing strategies, several limitations of bacteriocins, such as the high cost of isolation and purification, narrow spectrum of activity, low stability and solubility, and easy enzymatic degradation, need to be improved. Nanomaterials are promising agents in many biological applications. They are widely used in the conjugation or decoration of bacteriocins to augment the activity of bacteriocins or reduce problems related to their use in biomedical applications. Therefore, bacteriocins combined with nanomaterials have emerged as promising molecules that can be used in various biomedical applications. This review highlights the features of bacteriocins and their limitations in biomedical applications and provides a detailed overview of the uses of different nanomaterials in improving the limitations. Our review focuses on the potential applications of nanomaterials combined with bacteriocins as new designer molecules for use in future therapeutic strategies.

Bacteriocins as a new generation of antimicrobials: toxicity aspects and regulations

In recent decades, bacteriocins have received substantial attention as antimicrobial compounds. Although bacteriocins have been predominantly exploited as food preservatives, they are now receiving increased attention as potential clinical antimicrobials and as possible immune-modulating agents. Infections caused by antibiotic-resistant bacteria have been declared as a global threat to public health. Bacteriocins represent a potential solution to this worldwide threat due to their broad- or narrow-spectrum activity against antibiotic-resistant bacteria. Notably, despite their role in food safety as natural alternatives to chemical preservatives, nisin remains the only bacteriocin legally approved by regulatory agencies as a food preservative. Moreover, insufficient data on the safety and toxicity of bacteriocins represent a barrier against the more widespread use of bacteriocins by the food and medical industry. Here, we focus on the most recent trends relating to the application of bacteriocins, their toxicity and impacts.

Current approaches and future prospects of nanofibers: a special focus on antimicrobial drug delivery

Antibacterial nanofibers have a great potential for effective treatment of infections. They act as drug reservoir systems that release higher quantities of antibacterial agents/drug in a controlled manner at infection sites and prevent drug resistance, while concomitantly decreasing the systemic toxicity. With this drug delivery system, it is also possible to achieve multiple drug entrapment and also simultaneous or sequential release kinetics at the site of action. Therefore, advances in antibacterial nanofibers as drug delivery systems were overviewed within this article. Recently published data on antibacterial drug delivery was also summarised to provide a view of the current state of art in this field. Although antibacterial use seems to be limited and one can ask that 'what is left to be discovered?'; recent update literatures in this field highlighted the use of nanofibers from very different perspectives. We believe that readers will be benefiting this review for enlightening of novel ideas.

Enterococcus faecium CMUL1216 an Immunobiotic Strain with a Potential Application in Animal Sector

Antibiotic misuse in the animal sector is the first cause of the emergence and spreading of MDR bacteria. Prevention of infectious diseases and enhancement of animal growth are the main effects of antibiotics that push farmers and veterinarians to use this molecule in animal farms. Thus, the use of alternative solutions such as natural antimicrobial substances as well as probiotic strains is a crucial need in this sector. Enterococcus faecium CMUL1216 was isolated from healthy human baby's feces. This strain was assessed in vitro for probiotic properties including activity against many pathogens isolated from animal, human, and soil samples. CMUL1216 strain exhibits good antimicrobial activity against indicator pathogens in both planktonic and biofilm forms. In addition, CMUL1216 strain showed a strong biofilm formation. Furthermore, CMUL1216 exhibits a good anti-inflammatory effect by inducing the secretion of IL-10 in vitro. Moreover, this strain did not show any pathogenic characteristics such as hemolytic effect, presence of virulence genes as well as susceptibility to the majority of antibiotic families. E. faecium CMUL1216 could be a good candidate to be used a probiotic strain in the animal sector in order to maintain animal health and therefore reduce antibiotic resistance caused by the excessive use in this sector.

Last Call for Replacement of Antimicrobials in Animal Production: Modern Challenges, Opportunities, and Potential Solutions

The constant market demand for easily available and cheap food of animal origin necessitates an increasing use of antibiotics in animal production. The alarming data provided by organizations monitoring drug resistance in indicator and pathogenic bacteria isolated from humans and animals indicate a possible risk of a return to the preantibiotic era. For this reason, it seems that both preventive and therapeutic measures, taken as an alternative to antimicrobials, seem not only advisable but also necessary. Nevertheless, the results of various studies and market analyses, as well as difficulties in the implementation of alternative substances into veterinary medicine, do not guarantee that the selected alternatives will completely replace antimicrobials in veterinary medicine and animal production on a global scale. This publication is a brief overview of the drug resistance phenomenon and its determinants, the steps taken to solve the problem, including the introduction of alternatives to antimicrobials, and the evaluation of some factors influencing the potential implementation of alternatives in animal production. The review also presents two groups of alternatives, which, given their mechanism of action and spectrum, are most comparable to the effectiveness of antibiotics, as emphasized by the authors.

Interplay between gut microbiota and antimicrobial peptides

The gut microbiota is comprised of a diverse array of microorganisms that interact with immune system and exert crucial roles for the health. Changes in the gut microbiota composition and functionality are associated with multiple diseases. As such, mobilizing a rapid and appropriate antimicrobial response depending on the nature of each stimulus is crucial for maintaining the balance between homeostasis and inflammation in the gut. Major players in this scenario are antimicrobial peptides (AMP), which belong to an ancient defense system found in all organisms and participate in a preservative co-evolution with a complex microbiome. Particularly increasing interactions between AMP and microbiota have been found in the gut. Here, we focus on the mechanisms by which AMP help to maintain a balanced microbiota and advancing our understanding of the circumstances of such balanced interactions between gut microbiota and host AMP. This review aims to provide a comprehensive overview on the interplay of diverse antimicrobial responses with enteric pathogens and the gut microbiota, which should have therapeutic implications for different intestinal disorders.

Successful Development of Bacteriocins into Therapeutic Formulation for Treatment of MRSA Skin Infection in a Murine Model

The emergence of antibiotic-resistant pathogens has caused a serious worldwide problem in infection treatment in recent years. One of the pathogens is methicillin-resistant Staphylococcus aureus (MRSA), which is a major cause of skin and soft tissue infections. Alternative strategies and novel sources of antimicrobials to solve antibiotic resistance problems are urgently needed. In this study, we explored the potential of two broad-spectrum bacteriocins, garvicin KS and micrococcin P1, in skin infection treatments.

The emergence of antibiotic-resistant pathogens has caused a serious worldwide problem in infection treatment in recent years. One of the pathogens is methicillin-resistant Staphylococcus aureus (MRSA), which is a major cause of skin and soft tissue infections. Alternative strategies and novel sources of antimicrobials to solve antibiotic resistance problems are urgently needed. In this study, we explored the potential of two broad-spectrum bacteriocins, garvicin KS and micrococcin P1, in skin infection treatments. The two bacteriocins acted synergistically with each other and with penicillin G in killing MRSA in vitro. The MICs of the antimicrobials in the three-component mixture were 40 ng/ml for micrococcin P1 and 2 μg/ml for garvicin KS and penicillin G, which were 62, 16, and at least 1,250 times lower than their MICs when assessed individually. To assess its therapeutic potential further, we challenged the three-component formulation in a murine skin infection model with the multidrug-resistant luciferase-tagged MRSA Xen31, a strain derived from the clinical isolate S. aureus ATCC 33591. Using the tagged-luciferase activity as a reporter for the presence of Xen31 in wounds, we demonstrated that the three-component formulation was efficient in eradicating the pathogen from treated wounds. Furthermore, compared to Fucidin cream, which is an antibiotic commonly used in skin infection treatments, our formulation was also superior in terms of preventing resistance development.

Staphylococcins: an update on antimicrobial peptides produced by staphylococci and their diverse potential applications

Staphylococcins are antimicrobial peptides or proteins produced by staphylococci. They can be separated into different classes, depending on their amino acid composition, structural complexity, and steps involved in their production. In this review, an overview of the current knowledge on staphylococcins will be presented with emphasis on the information collected in the last decade, including a brief description of new peptides. Most staphylococcins characterized to date are either lantibiotics or linear class II bacteriocins. Recently, gene clusters coding for production of circular bacteriocins, sactipeptides, and thiopeptides have been mined from the genome of staphylococcal isolates. In contrast to class II bacteriocins, lantibiotics, sactipeptides, and thiopeptides undergo post-translational modifications that can be quite extensive, depending on the peptide. Few staphylococcins inhibit only some staphylococcal species, but most of them have proven to target pathogens belonging to different genera and involved in a variety of infectious diseases of clinical or agronomic importance. Therefore, these peptides exhibit potential application as anti-infective drugs in different areas. This review will also cover this diverse and remarkable potential. To be commercialized, however, staphylococcin production should be cost-effective and result in high bacteriocin yields, which are not generally achieved from the culture supernatant of their native producers. Such low yields make their production quite costly and not suitable at large industrial scale. Efforts already made to overcome this limitation, minimizing costs and time of production of some staphylococcins and employing either chemical synthesis or in vivo biosynthesis, will be addressed in this review as well. KEY POINTS: • Staphylococci produce a variety of antimicrobial peptides known as staphylococcins. • Most staphylococcins are post-translationally modified peptides. • Staphylococcins exhibit potential biotechnological applications. Graphical abstract.

Reducing Meat Perishability through Pullulan Active Packaging

The provision of safe products from the meat industry has been considered as the major source of protein for maintaining human health. Meat-borne outbreaks are mainly due to Salmonella typhimurium (S. typhimurium), Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Clostridium perfringens (C. perfringens), reducing the shelf life and consumer demands. A variety of vulnerable substances, including cholesterol oxidation products (COPs), are generated by the oxidation of meat induced by the microbial infestations. The use of certain biodegradable active packaging, including pullulan active packaging, is being focused by the meat industry due to their safety, stability, and negligible health risks. The potential of pullulan active packaging, incorporated with silver nanoparticles and essential oils, against E. coli, S. typhimurium, Mycoplasma, and other bacterial species is exclusive. Similarly, maintenance of organoleptic properties of meat with nominal oxidative rancidity and limited human health issues can be acquired by pullulan active packaging.

BacSJ-Another Bacteriocin with Distinct Spectrum of Activity that Targets Man-PTS

Lactic acid bacteria produce diverse antimicrobial peptides called bacteriocins. Most bacteriocins target sensitive bacteria by binding to specific receptors. Although a plethora of bacteriocins have been identified, for only a few of them the receptors they recognize are known. Here, we identified permease IIC and surface protein IID, two membrane subunits of the mannose-specific quaternary phosphotransferase system (Man-PTS), as a receptor for BacSJ, a subclass IId bacteriocin produced by Lactobacillus paracasei subsp. paracasei BGSJ2-8. BacSJ shares 45% identity with another Man-PTS binding bacteriocin, garvicin Q (GarQ). Similarly to GarQ, BacSJ has a relatively broad activity spectrum acting against several Gram-positive bacteria, such as Lactococcus lactis and Listeria monocytogenes, harboring fairly similar Man-PTSs, but not against Lactococcus garvieae. To identify specific Man-PTS amino acids responsible for the L.lactis sensitivity to BacSJ, and thus likely involved in the interaction with this bacteriocin, we generated eight independent BacSJ resistant L.lactis mutants harboring five distinct missense mutations in the ptnC or ptnD genes encoding the IIC and IID subunits. Concurrently with the resistance to BacSJ, the mutants efficiently utilized mannose as a carbon source, which indicated functionality of their mutated Man-PTS. The amino acid substitutions in the mutants localized to the intracellular region of the IIC permease or to the extracellular parts of IID. This localization coincides with regions targeted by GarQ and some other Man-PTS-binding garvicins, pointing to similarities between all these bacteriocins in the mechanism of their interaction with Man-PTS. During the attack by these bacteriocins, subunits IID and IIC are assumed to function sequentially as a docking and an entry module allowing the toxic peptide to bind the cell and then open the pore. However, since not all of the BacSJ-resistant mutants exhibited cross-resistance to GarQ, we propose that BacSJ interacts with Man-PTS in a manner slightly different from that of GarQ.

Application of bacteriocins in food preservation and infectious disease treatment for humans and livestock: a review

Infectious diseases caused by bacteria that can be transmitted via food, livestock and humans are always a concern to the public, as majority of them may cause severe illnesses and death. Antibacterial agents have been investigated for the treatment of bacterial infections. Antibiotics are the most successful antibacterial agents that have been used widely for decades to ease human pain caused by bacterial infections. Nevertheless, the emergence of antibiotic-resistant bacteria has raised awareness amongst public about the downside of using antibiotics. The threat of antibiotic resistance to global health, food security and development has been emphasized by the World Health Organization (WHO), and research studies have been focused on alternative antimicrobial agents. Bacteriocin, a natural antimicrobial peptide, has been chosen to replace antibiotics for its application in food preservation and infectious disease treatment for livestock and humans, as it is less toxic.

Killing or inhibition actions of (a) antibiotics and (b) bacteriocin on gut microbiota.

Crystal structure and site-directed mutagenesis of circular bacteriocin plantacyclin B21AG reveals cationic and aromatic residues important for antimicrobial activity

Plantacyclin B21AG is a circular bacteriocin produced by Lactiplantibacillus plantarum B21 which displays antimicrobial activity against various Gram-positive bacteria including foodborne pathogens, Listeria monocytogenes and Clostridium perfringens. It is a 58-amino acid cyclised antimicrobial peptide, with the N and C termini covalently linked together. The circular peptide backbone contributes to remarkable stability, conferring partial proteolytic resistance and structural integrity under a wide temperature and pH range. Here, we report the first crystal structure of a circular bacteriocin from a food grade Lactobacillus. The protein was crystallised using the hanging drop vapour diffusion method and the structure solved to a resolution of 1.8 Å. Sequence alignment against 18 previously characterised circular bacteriocins revealed the presence of conserved charged and aromatic residues. Alanine substitution mutagenesis validated the importance of these residues. Minimum inhibitory concentration analysis of these Ala mutants showed that Phe⁸Ala and Trp⁴⁵Ala mutants displayed a 48- and 32-fold reduction in activity, compared to wild type. The Lys¹⁹Ala mutant displayed the weakest activity, with a 128-fold reduction. These experiments demonstrate the relative importance of aromatic and cationic residues for the antimicrobial activity of plantacyclin B21AG and by extension, other circular bacteriocins sharing these evolutionarily conserved residues.

Characterisation of Bacteriocins Produced by Lactobacillus spp. Isolated from the Traditional Pakistani Yoghurt and Their Antimicrobial Activity against Common Foodborne Pathogens

Lactic acid bacteria (LAB) are widely known for their probiotic activities for centuries. These bacteria synthesise some secretory proteinaceous toxins, bacteriocins, which help destroy similar or interrelated bacterial strains. This study was aimed at characterising bacteriocins extracted from Lactobacillus spp. found in yoghurt and assessing their bactericidal effect on foodborne bacteria. Twelve isolated Lactobacillus spp. were examined to produce bacteriocins by the organic solvent extraction method. Bacteriocins produced by two of these strains, Lactobacillus helveticus (BLh) and Lactobacillus plantarum (BLp), showed the most significant antimicrobial activity, especially against Staphylococcus aureus and Acinetobacter baumannii. Analysis of SDS-PAGE showed that L. plantarum and L. helveticus bacteriocins have a molecular weight of ~10 kDa and ~15 kDa, respectively. L. plantarum (BLp) bacteriocin was heat stable while L. helveticus (BLh) bacteriocin was heat labile. Both bacteriocins have shown activity at acidic pH. Exposure to a UV light enhances the activity of the BLh; however, it had negligible effects on the BLp. Different proteolytic enzymes confirmed the proteinaceous nature of both the bacteriocins. From this study, it was concluded that bacteriocin extracts from L. helveticus (BLh) can be considered a preferable candidate against foodborne pathogens as compared to L. plantarum (BLp). These partially purified bacteriocins should be further processed to attain purified product that could be useful for food spoilage and preservation purposes.

Evaluation of Topical Lysostaphin as a Novel Treatment for Instrumented Rhesus Macaques (Macaca mulatta) Infected with Methicillin-Resistant Staphylococcus aureus

Lytic enzymes are novel antimicrobial agents that degrade bacterial cell walls, resulting in cell rupture and death. We tested one enzyme, the bacteriocin lysostaphin, for treatment of nonhuman primates (Macaca mulatta) with persistent methicillinresistant Staphylococcus aureus (MRSA) infection of their cranial implant margins. The goal of this study was to determine if topical lysostaphin, either alone or as an adjunct therapy, could eliminate MRSA. Lysostaphin had in vitro lytic activity against all 4 previously identified NHP MRSA clones, as well as against 12 MRSA isolates of the same clonal type (MLST ST3862 and spa type t4167) before and after treatment, with no resistance discovered. In an in vivo pilot study, a 2-d application of lysostaphin alone reduced MRSA in the implant margins by 3-logs during treatment of one animal; however, MRSA titers had returned to control levels by 1 wk after treatment. In the main study, all animals (n = 4) received 10 d of systemic antibiotic treatment and both the animals and their environment (cages, equipment, room) underwent 5-d of decontamination. The experimental animals (n = 2) received 5 doses of topical lysostaphin (15 mg, every other day) applied onto their implant margins. Daily cultures showed that MRSA counts decreased significantly (≤ 25 colony-forming units/mL; P < 0.05). However, sampling of the cranial implant margin 7 d after last treatment showed that MRSA counts had returned to control levels. Our study suggests that lysostaphin, coupled with other treatment modalities, can decrease MRSA infection short-term but do not completely eradicate MRSA in the long-term. This reappearance of MRSA may be due to cross-contamination or reinfection from other infected areas, an inability of the treatment to reach all colonized areas, or insufficient dosing or length of treatment. Topical lysostaphin may be more useful clinically for superficial nonimplant associated wounds in which the lytic enzyme has better access to the infected tissue.

Novel Topical Application of a Postbiotic, LactoSporin®, in Mild to Moderate Acne: A Randomized, Comparative Clinical Study to Evaluate its Efficacy, Tolerability and Safety

Acne vulgaris is a common skin disorder of pilosebaceous units. The therapy for mild-to-moderate acne includes topical antibiotics, benzoyl peroxide and retinoids. In this open-label, randomized monocentric study, we compared the efficacy of LactoSporin® 2% w/w cream with benzoyl peroxide in 64 male and female subjects with mild-to-moderate acne for three weeks. The efficacy parameters were evaluated based on the dermatologist visual assessment and instrumental measurements using Sebumeter® MPA580, Antera 3DTM and VISIA CR 2.2 and subject self-assessment questionnaires. Adverse events were recorded throughout the study period. In order to understand the mechanism of action and properties of LactoSporin, the pH stability, thermostability, antimicrobial activity and 5-alpha reductase activity were evaluated in vitro. A significant improvement was observed in the dermatological assessment of closed comedones (p < 0.0001), open comedones (p = 0.0069) and papules count (p < 0.0001) in comparison to the baseline in both LactoSporin and benzoyl peroxide groups. The antera analysis showed significant improvement in redness (p < 0.0001) and elevation (p < 0.0001) (small and medium) in both the treatment groups. The sebumeter analysis showed a significant decrease in sebaceous secretion (p < 0.0001) for LactoSporin, which resulted in reduced oiliness, pimples, acne spots and redness around the acne spot. The product was found to be safe without any irritancy. LactoSporin was stable at an acidic pH and temperature range of 70 to 90 °C, with antimicrobial activity against various pathogenic bacteria, including Cutibacterium acnes. It was also a potent inhibitor of 5-alpha reductase activity. Thus, it can be concluded that the efficacy of LactoSporin is equivalent to benzoyl peroxide in the treatment of mild-to-moderate acne lesions and better than benzoyl peroxide for reducing the sebaceous secretion and oily, greasy nature of the skin, implying its efficacy in other sebohorriec conditions.

A Novel Weissella cibaria Strain UTNGt21O Isolated from Wild Solanum quitoense Fruit: Genome Sequence and Characterization of a Peptide with Highly Inhibitory Potential toward Gram-Negative Bacteria

A novel Weissella cibaria strain UTNGt21O from the fruit of the Solanum quitoense (naranjilla) shrub produces a peptide that inhibits the growth of both Salmonella enterica subsp. enterica ATCC51741 and Escherichia coli ATCC25922 at different stages. A total of 31 contigs were assembled, with a total length of 1,924,087 bases, 20 contig hits match the core genome of different groups within Weissella, while for 11 contigs no match was found in the database. The GT content was 39.53% and the genome repeats sequences constitute around 186,760 bases of the assembly. The UTNGt21O matches the W. cibaria genome with 83% identity and no gaps (0). The sequencing data were deposited in the NCBI Database (BioProject accessions: PRJNA639289). The antibacterial activity and interaction mechanism of the peptide UTNGt21O on target bacteria were investigated by analyzing the growth, integrity, and morphology of the bacterial cells following treatment with different concentrations (1×, 1.5× and 2× MIC) of the peptide applied alone or in combination with chelating agent ethylenediaminetetraacetic acid (EDTA) at 20 mM. The results indicated a bacteriolytic effect at both early and late target growth at 3 h of incubation and total cell death at 6 h when EDTA was co-inoculated with the peptide. Based on BAGEL 4 (Bacteriocin Genome Mining Tool) a putative bacteriocin having 33.4% sequence similarity to enterolysin A was detected within the contig 12. The interaction between the peptide UTNGt21O and the target strains caused permeability in a dose-, time- response manner, with Salmonella (3200 AU/mL) more susceptible than E. coli (6400 AU/mL). The results indicated that UTNGt21O may damage the integrity of the cell target, leading to release of cytoplasmic components followed by cell death. Differences in membrane shape changes in target cells treated with different doses of peptide were observed by transmission electronic microscopy (TEM). Spheroplasts with spherical shapes were detected in Salmonella while larger shaped spheroplasts with thicker and deformed membranes along with filamentous cells were observed in E. coli upon the treatment with the UTNGt21O peptide. These results indicate the promising potential of the putative bacteriocin released by the novel W. cibaria strain UTNGt21O to be further tested as a new antimicrobial substance.

Discovery and characterisation of circular bacteriocin plantacyclin B21AG from Lactiplantibacillus plantarum B21

Lactiplantibacillus plantarum B21 isolated from Vietnamese sausage (nem chua) has previously displayed broad antimicrobial activity against Gram-positive bacteria including foodborne pathogens Listeria monocytogenes and Clostridium perfringens. This study successfully identified the antimicrobial agent as plantacyclin B21AG, a 5668 Da circular bacteriocin demonstrating high thermostability, resistance to a wide range of pH, proteolytic resistance and temporal stability. We report a reverse genetics approach to identify and characterise plantacyclin B21AG from first principles. The bacteriocin was purified from culture supernatant by a three-step process consisting of concentration, n-butanol extraction and cation exchange chromatography. A de novo peptide sequencing using LC-MS/MS techniques identified two putative peptide fragments which were mapped to the genome sequence of L. plantarum B21. This revealed an ORF corresponding to a putative circular bacteriocin with a 33-amino acid leader peptide and a 58-amino acid mature peptide encoded on a native plasmid pB21AG01. The bacteriocin is shown to be a small cationic predominantly α-helical protein (69%). The corresponding gene cluster, consisted of seven genes associated with post-translational circularisation, immunity and secretion. Whilst plantacyclin B21AG is 86% identical to the newly published plantaricyclin A it is more highly cationic having a net charge of +3 due to an additional basic residue in the putative membrane interaction region. This and other substitutions may well go some way to explaining functional differences. The robust nature of plantacyclin B21AG, its antimicrobial activity and associated machinery for cyclisation make it an interesting biotechnological target for development, both as a food-safe antimicrobial or potentially a platform technology for recombinant protein circularisation.

Unraveling microbial fermentation features in kimchi: from classical to meta-omics approaches

Kimchi is a traditional Korean fermented food prepared via spontaneous fermentation by various microorganisms originating from vegetables such as kimchi cabbage, radishes, and garlic. Recent advances in meta-omics approaches that integrate metataxonomics, metagenomics, metatranscriptomics, and metabolomics have contributed to explaining and understanding food fermentation processes. Kimchi microbial communities are composed of majorly lactic acid bacteria such as Leuconostoc, Lactobacillus, and Weissella and fewer eukaryotic microorganisms and kimchi fermentation are accomplished by complex microbial metabolisms to produce diverse metabolites such as lactate, acetate, CO₂, ethanol, mannitol, amino acids, formate, malate, diacetyl, acetoin, and 2, 3-butanediol, which determine taste, quality, health benefit, and safety of fermented kimchi products. Therefore, in the future, kimchi researches should be systematically performed using the meta-omics approaches to understand complex microbial metabolisms during kimchi fermentation. KEY POINTS: • Spontaneous fermentation by raw material microbes gives kimchi its unique flavor. • The kimchi microbiome is altered by environmental factors and raw materials. • Through the multi-omics approaches, it is possible to accurately analyze the diversity and metabolic characteristics of kimchi microbiome and discover potential functionalities.

The bactericidal efficacy of femtosecond laser-based therapy on the most common infectious bacterial pathogens in chronic wounds: an in vitro study

We investigated the influence of femtosecond laser irradiation on the growth of the two most common infectious bacterial pathogens in wounds; Staphylococcus aureus and Pseudomonas aeruginosa as an attempt to validate optimum parameters for a laser-based bactericidal modality to be used clinically. Bacterial cultures were exposed to femtosecond laser irradiation at different wavelengths, exposure times, and laser powers. The source of femtosecond laser was INSPIRE HF100 laser system, Spectra-Physics, which is pumped by a mode-locked femtosecond Ti: sapphire laser MAI TAI HP, Spectra-Physics. After irradiation, bacterial cells' survival was monitored by observing the clear zones of inhibition in cultured agar plates. Results for all strains indicated that the exposure to femtosecond laser irradiation with a wavelength ranging from ultraviolet (λ > 350 nm) to blue laser light (λ < 480 nm), for a period above 20 min and with a power density of ≈ 0.063 W/cm², was enough to inhibit both bacterial pathogens with the results maintained for 1 week following irradiation.

Phylogenomic Classification and Biosynthetic Potential of the Fossil Fuel-Biodesulfurizing Rhodococcus Strain IGTS8

Rhodococcus strain IGTS8 is the most extensively studied model bacterium for biodesulfurization of fossil fuels via the non–destructive sulfur–specific 4S pathway. This strain was initially assigned to Rhodococcus rhodochrous and later to Rhodococcus erythropolis thus making its taxonomic status debatable and reflecting the limited resolution of methods available at the time. In this study, phylogenomic analyses of the whole genome sequences of strain IGTS8 and closely related rhodococci showed that R. erythropolis and Rhodococcus qingshengii are very closely related species, that Rhodococcus strain IGTS8 is a R. qingshengii strain and that several strains identified as R. erythropolis should be re-classified as R. qingshengii. The genomes of strains assigned to these species contain potentially novel biosynthetic gene clusters showing that members of these taxa should be given greater importance in the search for new antimicrobials and other industrially important biomolecules. The plasmid-borne dsz operon encoding fossil fuel desulfurization enzymes was present in R. qingshengii IGTS8 and R. erythropolis XP suggesting that it might be transferable between members of these species.

Effects of Bacillus subtilis PB6 and/or chromium propionate supplementation on serum chemistry, complete blood count, and fecal Salmonella spp. count in high-risk cattle during the feedlot receiving and finishing periods. Transl Anim Sci 2020;4:txaa164. [PMID: 33134874 PMCID: PMC7584394 DOI: 10.1093/tas/txaa164]

The study objective was to determine the effects of Bacillus subtilis PB6 and/or chromium propionate supplementation on serum chemistry, complete blood count, and fecal Salmonella spp. count in high-risk beef cattle during a 56-d feedlot receiving period and the subsequent finishing period. Four truckload blocks of crossbred beef bulls (n = 300) and steers [n = 84; total n = 384; average initial body weight (BW) = 220 ± 16.2 kg] were sourced from regional auction markets and assigned randomly to treatments arranged in a 2 × 2 factorial. Blood samples were collected from two bulls nearest to the median BW on arrival in each pen (n = 96) and fecal samples were collected from cattle in block 3 (n = 96). The generalized complete block design consisted of 12 pen replications per treatment with pen as the experimental unit. Treatments were: 1) negative control (CON); 2) 13 g per animal daily of prepared B. subtilis PB6 product (CST); 3) 450 ppb dry matter (DM) chromium propionate (CHR); and 4) 13 g per animal daily of prepared B. subtilis PB6 product and 450 ppb DM chromium propionate (CST + CHR). Treatments were top dressed in feed bunks daily using 0.45 kg per animal ground corn carrier immediately following feed delivery. Data were analyzed using mixed models with repeated measures. Day affected all serum chemistry variables (P ≤ 0.03) except total CO2 (P = 0.34) and all complete blood count variables during receiving (P ≤ 0.02) except percentage basophils (P ≥ 0.12). During the overall receiving period, serum calcium was decreased (P = 0.02) by CHR. Cattle fed CHR had greater total leukocyte count (P = 0.04) and neutrophil count (P = 0.02) during the overall receiving period. Fecal Salmonella spp. count was markedly reduced in cattle fed CST on day 28 (P = 0.01) and overall (P = 0.07). Overall, these data provide metabolic and hematologic insight into the unique challenges presented by lightweight, high-risk feeder cattle. Notably, CST was found to be effective in mitigating fecal enumeration and presumably replication of Salmonella spp. in the gastrointestinal tract.

Purification, Characterization, Identification, and Anticancer Activity of a Circular Bacteriocin From Enterococcus thailandicus

New anticancer agents are continually needed because cancerous cells continue to evolve resistance to the currently available chemotherapeutic agents. The aim of the present study was to screen, purify and characterize a hepatotoxic bacteriocin from Enterococcus species. The production of bacteriocin from the Enterococcus isolates was achieved based on their antibacterial activity against indicator reference strains. Enterococcus isolates showed a broad spectrum of antibacterial activity by forming inhibition zones with diameters ranged between 12 and 29 mm. The most potent bacteriocin producing strain was molecularly identified as Enterococcus thailandicus. The crude extracted bacteriocin was purified by cation exchange and size exclusion chromatography that resulted in 83 fractions. Among them, 18 factions were considered as bacteriocins based on their positive antibacterial effects. The anticancer effects of the purified bacteriocins were tested against HepG2 cell line. The most promising enterocin (LNS18) showed the highest anticancer effects against HepG2 cells (with 75.24% cellular inhibition percentages), with IC50 value 15.643 μM and without any significant cytotoxic effects on normal fibroblast cells (BJ ATCC® CRL-2522™). The mode of anticancer action of enterocin LNS18 against HepG2 cells could be explained by its efficacy to induce cellular ROS, decrease HepG2 CD markers and arrest cells in G0 phase. Amino acid sequence of enterocin LNS18 was determined and the deduced peptide of the structural gene showed 86 amino acids that shared 94.7% identity with enterocin NKR-5-3B from E. faecium. Enterocin LNS18 consisted of 6 α-helices; 5 circular and one linear. Model-template alignment constructed between enterocin LNS18 and NKR-5-3B revealed 95.31% identity. The predicted 3D homology model of LNS18, after circularization and release of 22 amino acids, showed the formation of a bond between Leu23 and Trp86 amino acid residues at the site of circularization. Furthermore, areas of positive charges were due to the presence of 6 lysine residues resulting in a net positive charge of +4 on the bacteriocin surface. Based on the above mentioned results, our characterized bacteriocin is a promising agent to target liver cancer without any significant toxic effects on normal cell lines.

Development of a novel anti-biofilm peptide derived from profilin of Spodoptera frugiperda

Candida yeast infections are the fourth leading cause of death worldwide. Peptides with antimicrobial activity are a promising alternative treatment for such infections. Here, the antifungal activity of a new antimicrobial peptide-PEP-IA18-was evaluated against Candida species. PEP-IA18 was designed from the primary sequence of profilin, a protein from Spodoptera frugiperda, and displayed potent activity against Candida albicans and Candida tropicalis, showing a minimum inhibitory concentration (MIC) of 2.5 µM. Furthermore, the mechanism of action of PEP-IA18 involved interaction with the cell membrane (ergosterol complexation). Treatment at MIC and/or 10 × MIC significantly reduced biofilm formation and viability. PEP-IA18 showed low toxicity toward human fibroblasts and only revealed hemolytic activity at high concentrations. Thus, PEP-IA18 exhibited antifungal and anti-biofilm properties with potential applicability in the treatment of infections caused by Candida species.

Comparative Genomic Analysis Provides Insights into the Phylogeny, Resistome, Virulome, and Host Adaptation in the Genus Ewingella

Ewingella americana is a cosmopolitan bacterial pathogen that has been isolated from many hosts. Here, we sequenced a high-quality genome of E. americana B6-1 isolated from Flammulina filiformis, an important cultivated mushroom, performed a comparative genomic analysis with four other E. americana strains from various origins, and tested the susceptibility of B6-1 to antibiotics. The genome size, predicted genes, and GC (guanine-cytosine) content of B6-1 was 4.67 Mb, 4301, and 53.80%, respectively. The origin of the strains did not significantly affect the phylogeny, but mobile genetic elements shaped the evolution of the genus Ewingella. The strains encoded a set of common genes for type secretion, virulence effectors, CAZymes, and toxins required for pathogenicity in all hosts. They also had antibiotic resistance, pigments to suppress or evade host defense responses, as well as genes for adaptation to different environmental conditions, including temperature, oxidation, and nutrients. These findings provide a better understanding of the virulence, antibiotic resistance, and host adaptation strategies of Ewingella, and they also contribute to the development of effective control strategies.

Bacteriocins, Antimicrobial Peptides from Bacterial Origin: Overview of Their Biology and Their Impact against Multidrug-Resistant Bacteria

Currently, the emergence and ongoing dissemination of antimicrobial resistance among bacteria are critical health and economic issue, leading to increased rates of morbidity and mortality related to bacterial infections. Research and development for new antimicrobial agents is currently needed to overcome this problem. Among the different approaches studied, bacteriocins seem to be a promising possibility. These molecules are peptides naturally synthesized by ribosomes, produced by both Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB), which will allow these bacteriocin producers to survive in highly competitive polymicrobial environment. Bacteriocins exhibit antimicrobial activity with variable spectrum depending on the peptide, which may target several bacteria. Already used in some areas such as agro-food, bacteriocins may be considered as interesting candidates for further development as antimicrobial agents used in health contexts, particularly considering the issue of antimicrobial resistance. The aim of this review is to present an updated global report on the biology of bacteriocins produced by GPB and GNB, as well as their antibacterial activity against relevant bacterial pathogens, and especially against multidrug-resistant bacteria.

The bacterial instrument as a promising therapy for colon cancer

OBJECTIVE

Colon cancer is a great health concern worldwide, as it is the second leading cause of cancer-related death. Conventional treatment of cancer such as surgery, radiotherapy, and chemotherapy are faced with limitations and side effects. Therefore, strategies for the treatment of cancer need to be modified or new strategies replacing the old one.

AIMS

The aim of this study is to review the role of bacteria or their products (such as peptides, bacteriocins, and toxins) as a therapeutic agent for colon cancer.

RESULTS AND CONCLUSION

Recently, the therapeutic role of bacteria and their products in colon cancer treatment holds promise as emerging novel anti-cancer agents. Unlike the conventional treatments, targeted therapy based on the use of bacteria that are able to directly target tumor cells without affecting normal cells is evolving as an alternative strategy. Moreover, several bacterial species were used in live, attenuated or genetically modified that are able to multiply selectively in tumors and inhibiting their growth.

Whole Genome Sequencing and Comparative Genomics of Two Nematicidal Bacillus Strains Reveals a Wide Range of Possible Virulence Factors

Bacillus firmus nematicidal bacterial strains are used to control plant parasitic nematode infestation of crops in agricultural production. Proteases are presumed to be the primary nematode virulence factors in nematicidal B. firmus degrading the nematode cuticle and other organs. We determined and compared the whole genome sequences of two nematicidal strains. Comparative genomics with a particular focus on possible virulence determinants revealed a wider range of possible virulence factors in a B. firmus isolate from a commercial bionematicide and a wild type Bacillus sp. isolate with nematicidal activity. The resulting 4.6 Mb B. firmus I-1582 and 5.3 Mb Bacillus sp. ZZV12-4809 genome assemblies contain respectively 18 and 19 homologs to nematode-virulent proteases, two nematode-virulent chitinase homologs in ZZV12-4809 and 28 and 36 secondary metabolite biosynthetic clusters, projected to encode antibiotics, small peptides, toxins and siderophores. The results of this study point to the genetic capability of B. firmus and related species for nematode virulence through a range of direct and indirect mechanisms.

Plantaricin NC8 αβ exerts potent antimicrobial activity against Staphylococcus spp. and enhances the effects of antibiotics

The use of conventional antibiotics has substantial clinical efficacy, however these vital antimicrobial agents are becoming less effective due to the dramatic increase in antibiotic-resistant bacteria. Novel approaches to combat bacterial infections are urgently needed and bacteriocins represent a promising alternative. In this study, the activities of the two-peptide bacteriocin PLNC8 αβ were investigated against different Staphylococcus spp. The peptide sequences of PLNC8 α and β were modified, either through truncation or replacement of all L-amino acids with D-amino acids. Both L- and D-PLNC8 αβ caused rapid disruption of lipid membrane integrity and were effective against both susceptible and antibiotic resistant strains. The D-enantiomer was stable against proteolytic degradation by trypsin compared to the L-enantiomer. Of the truncated peptides, β1–22, β7–34 and β1–20 retained an inhibitory activity. The peptides diffused rapidly (2 min) through the bacterial cell wall and permeabilized the cell membrane, causing swelling with a disorganized peptidoglycan layer. Interestingly, sub-MIC concentrations of PLNC8 αβ substantially enhanced the effects of different antibiotics in an additive or synergistic manner. This study shows that PLNC8 αβ is active against Staphylococcus spp. and may be developed as adjuvant in combination therapy to potentiate the effects of antibiotics and reduce their overall use.

Enterocin Structural Gene Screening in Enterococci from Pannon White Breed Rabbits

This study was focused on screening the most frequently occurring enterocin (Ents) genes in faecal enterococci from the Pannon White breed of rabbits, in which this parameter never has been tested. Enterococci tested were Ent genes absent, except Enterococcus faecium EF9a, which possessed genes for four Ents. Strains produced a high amount of lactic acid (1.25 ± 0.055 mmol/L, on average) and sufficiently tolerate bile. Inhibition activity of crude bacteriocin substance-partially purified (Ent, CE EF9a)-was tested against altogether 53 indicator strains. The growth of 38 strains of different staphylococcal species was not inhibited. However, the growth of fifteen other Gram-positive indicators was inhibited with inhibition activity ranged from 100 to 12,800 AU/mL. Listeria monocytogenes LM 7562 was the most susceptible to CE EF9a treatment (12,800 AU/mL). Molecular mass of CE EF9a ranged between 3000 and 10,000 Da. After heat treatment at different temperatures and time, CE EF9a was active with the inhibition activity 12,800 AU/mL. After storage of CE EF9a at different conditions, it was active even after 2-month storage at room temperature (200 AU/mL against LM 7562 strain). Inhibition activity of CE EF9a after 2-month storage at 4 °C was 1600 AU/mL and the most stable was CE EF9a at - 20 °C; the activity 12,800 AU/mL was kept still after 2 months. It indicates a small, thermostable substance; however, in further detail, purification analysis is necessary.

Purification and Characterization of an Antibacterial Substance from Aerococcus urinaeequi Strain HS36

A bacterial strain inhibiting the growth of Vibrio anguillarum, the causative agent of vibriosis, was isolated from fish intestines. The isolated strain HS36 was identified as Aerococcus urinaeequi based on the characteristics of the genus according to Bergey's Manual of Systematic Bacteriology and by 16S rRNA sequencing. The growth rate and antibacterial activity of strain HS36 in shaking culture were higher than those in static culture, while the optimal pH and temperature for antibacterial activity were 7.0 and 30°C, respectively. The active antibacterial substance was purified from a culture broth of A. urinaeequi HS36 by Sephadex G-75 gel chromatography, Sephadex G-25 gel chromatography, and reverse-phase high-performance liquid chromatography. Its molecular weight, as estimated by Tricine SDS-polyacrylamide gel electrophoresis, was approximately 1,000 Da. The antibacterial substance produced by strain HS36 was stable after incubation for 1 h at 100°C. Although its antibacterial activity was optimal at pH 6-8, activity was retained at a pH range from 2 to 11. The purified antibacterial substance was inactivated by proteinase K, papain, and β-amylase treatment. The newly purified antibacterial substance, classified as a class II bacteriocin, inhibited the growth of Klebsiella pneumoniae, Salmonella enterica, and Vibrio alginolyticus.

Comparative genomics of multidrug-resistant Enterococcus spp. isolated from wastewater treatment plants

BACKGROUND

Wastewater treatment plants (WWTPs) are considered hotspots for the environmental dissemination of antimicrobial resistance (AMR) determinants. Vancomycin-Resistant Enterococcus (VRE) are candidates for gauging the degree of AMR bacteria in wastewater. Enterococcus faecalis and Enterococcus faecium are recognized indicators of fecal contamination in water. Comparative genomics of enterococci isolated from conventional activated sludge (CAS) and biological aerated filter (BAF) WWTPs was conducted.

RESULTS

VRE isolates, including E. faecalis (n = 24), E. faecium (n = 11), E. casseliflavus (n = 2) and E. gallinarum (n = 2) were selected for sequencing based on WWTP source, species and AMR phenotype. The pangenomes of E. faecium and E. faecalis were both open. The genomic fraction related to the mobilome was positively correlated with genome size in E. faecium (p < 0.001) and E. faecalis (p < 0.001) and with the number of AMR genes in E. faecium (p = 0.005). Genes conferring vancomycin resistance, including vanA and vanM (E. faecium), vanG (E. faecalis), and vanC (E. casseliflavus/E. gallinarum), were detected in 20 genomes. The most prominent functional AMR genes were efflux pumps and transporters. A minimum of 16, 6, 5 and 3 virulence genes were detected in E. faecium, E. faecalis, E. casseliflavus and E. gallinarum, respectively. Virulence genes were more common in E. faecalis and E. faecium, than E. casseliflavus and E. gallinarum. A number of mobile genetic elements were shared among species. Functional CRISPR/Cas arrays were detected in 13 E. faecalis genomes, with all but one also containing a prophage. The lack of a functional CRISPR/Cas arrays was associated with multi-drug resistance in E. faecium. Phylogenetic analysis demonstrated differential clustering of isolates based on original source but not WWTP. Genes related to phage and CRISPR/Cas arrays could potentially serve as environmental biomarkers.

CONCLUSIONS

There was no discernible difference between enterococcal genomes from the CAS and BAF WWTPs. E. faecalis and E. faecium have smaller genomes and harbor more virulence, AMR, and mobile genetic elements than other Enterococcus spp.

Bacteriocins, Potent Antimicrobial Peptides and the Fight against Multi Drug Resistant Species: Resistance Is Futile?

Despite highly specialized international interventions and policies in place today, the rapid emergence and dissemination of resistant bacterial species continue to occur globally, threatening the longevity of antibiotics in the medical sector. In particular, problematic nosocomial infections caused by multidrug resistant Gram-negative pathogens present as a major burden to both patients and healthcare systems, with annual mortality rates incrementally rising. Bacteriocins, peptidic toxins produced by bacteria, offer promising potential as substitutes or conjugates to current therapeutic compounds. These non-toxic peptides exhibit significant potency against certain bacteria (including multidrug-resistant species), while producer strains remain insusceptible to the bactericidal peptides. The selectivity and safety profile of bacteriocins have been highlighted as superior advantages over traditional antibiotics; however, many aspects regarding their efficacy are still unknown. Although active at low concentrations, bacteriocins typically have low in vivo stability, being susceptible to degradation by proteolytic enzymes. Another major drawback lies in the feasibility of large-scale production, with these key features collectively limiting their current clinical application. Though such limitations require extensive research, the concept of expanding bacteriocins from food preservation to human health opens many fascinating doors, including novel drug delivery systems and anticancer treatment applications.

The importance of antimicrobial compounds produced by beneficial bacteria on the biocontrol of phytopathogens

Bacteria produce antimicrobial compounds to compete for nutrients and space in a particular habitat. Antagonistic interactions can be evaluated by several methodologies including the double-layer agar and simultaneous inhibition assays. Among the well-known inhibitory substances produced by bacteria are the broad-spectrum antibiotics, organic acids, siderophores, antifungal, and bacteriocins. The most studied bacterial genera able to produce these inhibitory substances are Enterococcus, Lactococcus, Streptomyces, Bacillus, Pseudomonas, Klebsiella, Escherichia, and Burkholderia. Some beneficial bacteria can promote plant growth and degrade toxic compounds in the environment representing an attractive solution to diverse issues in agriculture and soil pollution, particularly in fields with damaged soils where pesticides and fertilizers have been indiscriminately used. Beneficial bacteria may increase plant health by inhibiting pathogenic microorganisms; some examples include Gluconacetobacter diazotrophicus, Azospirullum brasilense, Pseudomonas fluorescens, Pseudomonas protegens, and Burkholderia tropica. However, most studies showing the antagonistic potential of these bacteria have been performed in vitro, and just a few of them have been evaluated in association with plants. Several inhibitory substances involved in pathogen antagonism have not been elucidated yet; in fact, we know only 1 % of the bacterial diversity in a natural environment leading us to assume that many other inhibitory substances remain unexplored. In this review, we will describe the characteristics of some antimicrobial compounds produced by beneficial bacteria, the principal methodologies performed to evaluate their production, modes of action, and their importance for biotechnological purposes.

Bioactivity of Bac70 Produced by Bacillus atrophaeus Strain DDBCC70

BACKGROUND

Recently, using antibacterial peptides has been considered as a strategy to manage the worldwide antibiotic-resistance crisis. Screening of Dasht-Desert Bacterial Culture Collection (DDBCC) for bacteriocin or bacteriocin-like producer was aimed in this study to introduce native antibacterial agent(s).

METHODS

In this study, 170 isolates were examined by the cross-streak method against G+ and G- indicators. Isolates with antimicrobial activity were compared using turbidity and well diffusion tests. The candidate isolate, DDBCC70, was molecularly and biochemically characterized. Then, the production of an antibacterial agent was physicochemically optimized. The supernatant was saturated ammonium sulfate. SDS-PAGE and Thin-Layer Chromatography (TLC) analyses, cytotoxicity, and hemagglutination tests were performed.

RESULTS

First, 23 isolates were detected with antimicrobial activity against at least three of the indicator strains. DDBCC70 was distinguished with the broad-spectrum of antibacterial effects of the Cell-Free Supernatants (CFSs). The black pigments on BHI and a 98% similarity in 16S rDNA and similarity in biochemical tests confirmed the strain of DDBCC70 as Bacillus atrophaeus (B. atrophaeus). The highest amount of the antibacterial agent, Bac70, was obtained from the modified brain heart infusion medium. It was revealed that 70% ammonium sulfate-saturated Bac70 was 3.8 and 1.6 times more effective on Pseudomonas aeuroginosa (P. aeuroginosa) and Klebsiella pneumoniae (K. pneumoniae). Bac70, a >25 kDa protein and a safe compound for blood cells, neither agglutinated human erythrocyte nor lysed sheep blood. The purified bacteriocin-like molecule destroyed biofilms from P. aeruginosa and Staphylococcus aureus (S. aureus). Moreover, the fraction of Bac70 from the TLC plate showed higher inhibitory effects against K. pneumoniae.

CONCLUSION

Based on the above-mentioned features, Bac70 is a potential alternative therapeutic agent in pharmaceutical, food preservative and biotech-related industries.

The biotechnological potential of marine bacteria in the novel lineage of Pseudomonas pertucinogena

Marine habitats represent a prolific source for molecules of biotechnological interest. In particular, marine bacteria have attracted attention and were successfully exploited for industrial applications. Recently, a group of Pseudomonas species isolated from extreme habitats or living in association with algae or sponges were clustered in the newly established Pseudomonas pertucinogena lineage. Remarkably for the predominantly terrestrial genus Pseudomonas, more than half (9) of currently 16 species within this lineage were isolated from marine or saline habitats. Unlike other Pseudomonas species, they seem to have in common a highly specialized metabolism. Furthermore, the marine members apparently possess the capacity to produce biomolecules of biotechnological interest (e.g. dehalogenases, polyester hydrolases, transaminases). Here, we summarize the knowledge regarding the enzymatic endowment of the marine Pseudomonas pertucinogena bacteria and report on a genomic analysis focusing on the presence of genes encoding esterases, dehalogenases, transaminases and secondary metabolites including carbon storage compounds.

Human skin microbiota is a rich source of bacteriocin-producing staphylococci that kill human pathogens

The demand for novel antimicrobial therapies due to the threat posed by antimicrobial resistance has resulted in a growing interest in the protective role of our skin bacteria and the importance of competition among bacteria on the skin. A survey of the cultivable bacteria on human skin was undertaken to identify the capacity of the skin microbiota to produce bacteriocins with activity against skin pathogens. Twenty-one bacteriocins produced by bacteria isolated from seven sites on the human body of each subject exhibited inhibition spectra ranging from broad to narrow range, inhibiting many Gram-positive bacteria, including opportunistic skin pathogens such as Propionibacterium acnes (recently renamed Cutibacterium acnes), Staphylococcus epidermidis and methicillin-resistant Staphylococcus aureus (MRSA). Sequencing indicated that the antimicrobial-producing isolates were predominately species/strains of the Staphylococcus genus. Colony mass spectrometry revealed peptide masses that do not correspond to known bacteriocins. In an era where antibiotic resistance is of major concern, the inhibitory effect of novel bacteriocins from the bacteria of skin origin demonstrates the antimicrobial potential that could be harnessed from within the human skin microbiota.

Comparison of Different Nisin Separation and Concentration Methods: Industrial and Cost-Effective Perspectives

Separation and concentration of biotechnological products are the most important steps of purification stage in downstream processing. In the present study, three nisin separation and concentration methods including salting out by ammonium sulfate, solvent extraction (at 20 °C, 4 °C, and - 10 °C) and direct chromatography of culture medium were compared with each other. According to our results, nisin precipitation by ammonium sulfate at 40% saturation was the most efficient method (yield = 90.04%, purification fold = 168.80). Low yield and fold purification values were obtained by solvent extraction with chloroform (yield = 24.23%, fold purification = 37.43 at - 10 °C) and direct cation exchange chromatography of culture medium (yield = 20.00%, fold purification = 1.80). Also, performing purification steps in low pH values and acidic conditions (pH = 3.0) is essential for efficient nisin purification.

ADAPTABLE: a comprehensive web platform of antimicrobial peptides tailored to the user's research

Antimicrobial peptides (AMPs) are part of the innate immune response to pathogens in all of the kingdoms of life. They have received significant attention because of their extraordinary variety of activities, in particular, as candidate drugs against the threat of super-bacteria. A systematic study of the relation between the sequence and the mechanism of action is urgently needed, given the thousands of sequences already in multiple web resources. ADAPTABLE web platform (http://gec.u-picardie.fr/adaptable) introduces the concept of "property alignment" to create families of property and sequence-related peptides (SR families). This feature provides the researcher with a tool to select those AMPs meaningful to their research from among more than 40,000 nonredundant sequences. Selectable properties include the target organism and experimental activity concentration, allowing selection of peptides with multiple simultaneous actions. This is made possible by ADAPTABLE because it not only merges sequences of AMP databases but also merges their data, thereby standardizing values and handling non-proteinogenic amino acids. In this unified platform, SR families allow the creation of peptide scaffolds based on common traits in peptides with similar activity, independently of their source.