Purification and Molecular Characterization of the Novel Highly Potent Bacteriocin TSU4 Produced by Lactobacillus animalis TSU4

Genomic insights from Lactiplantibacillus plantarum BRD3A isolated from Atingba, a traditional fermented rice-based beverage and analysis of its potential for probiotic and antimicrobial activity against Methicillin-resistant Staphylococcus aureus

Lactiplantibacillus plantarum BRD3A was isolated from Atingba, a traditional fermented rice-based beverage of Manipur. Its genomic sequence has 13 contigs and its genome size is 3,320,817 bp with a guanine-cytosine (GC) ratio of 44.6%. It comprises 3185 genes including 3112 coding sequences (CDSs), 73 RNAs (including 66 tRNAs and others), and one clustered regularly interspaced short palindromic repeat (CRISPR) array. A comparative and phylogenetic analysis with the Lp. plantarum genome shows that this strain has close similarity with other Lp. plantarum strains and about 99% average nucleotide identity. Functional annotation using evolutionary genealogy of genes-non-supervised orthologous groups (EggNOG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) reveals genes associated with various biological processes such as metabolism, genetic information processing, and transport functions. Furthermore, the strain harbors bacteriocins like plantaricin E, Plantaricin F, and Enterocin X categorized under class IIb by the BAGEL4 database, indicating its potential antimicrobial properties. Additionally, AntiSMASH web server predicted four secondary regions-T3PKS, terpene, cyclic lactone inducer, and ribosomally synthesized and post-translationally modified peptide (RiPP)-suggesting an even higher antimicrobial potential. We validated the antimicrobial activity of Lp. plantarum BRD3A through in vitro experiments in which it exhibited promising bactericidal effects on methicillin-resistant Staphylococcus aureus, inhibiting their biofilm growth. These findings indicate the potential of Lp. plantarum BRD3A to be used as an alternative to conventional antibiotics.

Nanomedicine for drug resistant pathogens and COVID-19 using mushroom nanocomposite inspired with bacteriocin – A Review

Multidrug resistant (MDR) pathogens have become a major global health challenge and have severely threatened the health of society. Current conditions have gotten worse as a result of the COVID-19 pandemic, and infection rates in the future will rise. It is necessary to design, respond effectively, and take action to address these challenges by investigating new avenues. In this regard, the fabrication of metal NPs utilized by various methods, including green synthesis using mushroom, is highly versatile, cost-effective, eco-compatible, and superior. In contrast, biofabrication of metal NPs can be employed as a powerful weapon against MDR pathogens and have immense biomedical applications. In addition, the advancement in nanotechnology has made possible to modify the nanomaterials and enhance their activities. Metal NPs with biomolecules composite to prevents their microbial adhesion and kills the microbial pathogens through biofilm formation. Bacteriocin is an excellent antimicrobial peptide that works well as an augmentation substance to boost the antimicrobial effects. As a result, we concentrate on the creation of new, eco-compatible mycosynthesized metal NPs with bacteriocin nanocomposite via electrostatic, covalent, or non-covalent bindings. The synergistic benefits of metal NPs with bacteriocin to combat MDR pathogens and COVID-19, as well as other biomedical applications, are discussed in this review. Moreover, the importance of the adverse outcome pathway (AOP) in risk analysis of manufactured metal nanocomposite nanomaterial and their future possibilities also discussed.

Antimicrobial Activity of Ligilactobacillus animalis SWLA-1 and Its Cell-Free Supernatant against Multidrug-Resistant Bacteria and Its Potential Use as an Alternative to Antimicrobial Agents

The emergence of multidrug-resistant (MDR) bacteria and the spread of antimicrobial resistance among various bacteria are major threats to the global community. Due to the increased failure of classical antibiotic treatments against MDR bacterial infections, probiotics and their antimicrobial compounds have been suggested as promising alternatives to deal with MDR bacteria. Various strains of lactic acid bacteria have been reported to produce antagonistic molecules against pathogens. A new strain of Ligilactobacillus animalis, L. animalis SWLA-1, isolated from the feces of healthy dogs, shows strong antimicrobial activity against not only common pathogens but also MDR bacteria. In this study, we compared the antimicrobial activity of L. animalis SWLA-1 with that of other lactobacilli and antibiotics using an agar spot assay. Additionally, a novel spot inhibition index was developed and validated to quantitively evaluate the inhibitory activities of lactobacilli and antibiotics. A competitive coculture assay of L. animalis SWLA-1 with MDR bacteria further demonstrated its antibacterial activity. Furthermore, we evaluated the antimicrobial activity of the cell-free supernatant (CFS) of L. animalis SWLA-1 and its stability under various conditions in vitro. We found that L. animalis SWLA-1 and its CFS are potential alternatives to classic antimicrobial agents.

Antimicrobial activity of dominant Ligilactobacillus animalis strains in healthy canine feces and their probiotic potential

The number of companion animals living with humans has continually increased over the last few decades, and so has the interest of owners and stakeholders in the animal food and probiotics industry. Currently, the probiotic bacteria added to the feed of companion animals predominantly originate from the lactic acid bacteria (LAB) used for humans; however, there are differences between the microbiota of humans and that of their companion animals. This study aimed to determine the dominant LAB in dog feces and investigate their functional properties. Ligilactobacillus animalis (formerly called Lactobacillus animalis) was identified as the dominant lactic acid bacterium in dog feces. It displayed various inhibitory effects against pathogenic and enteropathogenic bacteria. This finding suggests that Ligilactobacillus animalis can potentially be used in novel probiotics or as a food additive for dogs.

Evaluation of inhibitory compounds produced by bacteria isolated from a hydrogen-producing bioreactor during the self-fermentation of wheat straw

AIMS

The objective of this study was to evaluate the inhibitory activity of compounds secreted by bacteria isolated from a hydrogen-producing bioreactor to understand how these microorganisms interact in this community.

METHODS AND RESULTS

In vitro inhibitory assays were performed using samples secreted by bacteria subject to different treatments to determine if their inhibitory effect was due to organic acids, non-proteinaceous compounds, or bacteriocin-like inhibitory substances (BLIS). Bacterial isolated were suppressed 43%, 30%, and 27% by neutralized, precipitated, and non-neutralized cell-free supernatants, respectively. Non-hydrogen producers (Non-H₂ P) LAB (Lactobacillus plantarum LB1, L. pentosus LB7, Pediococcus acidilactici LB4) and hydrogen producers (H₂ P) LAB (Enterococcus faecium F) were inhibited by the production of organic acids, non-proteinaceous compounds, and BLIS. Meanwhile, the obligate anaerobe H₂ P (Clostridium beijerinckii B) inhibited by the production of non-proteinaceous compounds and BLIS. The presence of BLIS was confirmed when proteolytic enzymes affected the inhibitory activity of secreted proteins in values ranging from 20 to 42%. The BLIS produced by L. plantarum LB1, P. acidilactici LB4, L. pentosus LB7, and E. faecium F showed molecular masses of ~ 11 kDa, 25 kDa, 20 kDa, and 11 kDa, respectively.

CONCLUSIONS

It was demonstrated antagonistic interactions between Lactobacillus- Enterococcus, and Pediococcus-Enterococcus species, generated by the secretion of organic acids, non-proteinaceous compounds, and BLIS.

SIGNIFICANCE AND IMPACT OF THE STUDY

We report the interactions between LAB isolated from hydrogen-producing bioreactors. These interactions might impact the dynamics of the microbial population during hydrogen generation. Our work lays a foundation for strategies that allow controlling bacteria that can affect hydrogen production.

A review on characterization, applications and structure-activity relationships of Bacillus species-produced bacteriocins

Antimicrobial peptides (AMPs) are inherently occurring proteins that are produced by microorganisms as secondary metabolites. Members of genus Bacillus produce many types of AMPs by ribosomal (bacteriocins) and non-ribosomal (polymyxins and iturins) mechanisms. Bacteriocins are ribosomally synthesized peptides that inhibit the growth of closely related bacterial strains. Moreover, bacteriocins produced by Bacillus species have been widely used in pharmaceutical, food industry, fishery, livestock as well as in agriculture sector. The objective of this review is to assess the characterization of the Bacillus-derived bacteriocins, their potential use in different sectors and structure-activity relationships.

Synergistic Inhibition of Plantaricin E/F and Lactic Acid Against Aeromonas hydrophila LPL-1 Reveals the Novel Potential of Class IIb Bacteriocin

Plantaricin E/F (PlnEF) is a pair of two-component class IIb bacteriocin produced by lactic acid bacteria. PlnEF commonly displays potent antimicrobial activity against certain Gram-positive organisms. In this study, we investigated the synergistic activity of PlnEF combined with lactic acid against Gram-negative food and aquaculture potential pathogen Aeromonas hydrophila LPL-1, which is naturally resistant to PlnEF. We applied SDS-PAGE, wavelength-scanning, laser confocal microscopy, flow cytometer, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and two-dimensional electrophoresis to investigate their synergistic inhibitory activities. The results showed that L-lactic acid drove the release of LPS from A. hydrophila, making it possible for PlnEF to contact the inner cell membrane of A. hydrophila. Besides, co-treatment of lactic acid and PlnEF caused severe morphological and intracellular changes of A. hydrophila, including blebs on the cell surface, abnormal cell elongation, inner membrane disruption, pore-forming through the outer and inner membrane, coagulation of the cytoplasm, and structural transformation of DNA. Protein profile analysis revealed that combined treatment of lactic acid and PlnEF inhibited the energy metabolism, protein synthesis, protein folding, and DNA replication in A. hydrophila. These findings proved that PlnEF combined with lactic acid was efficient against A. hydrophila and shed light on bacteriocin’s potential and a new inhibition mechanism against A. hydrophila.

Bacteriocins: Properties and potential use as antimicrobials

A variety of bacteriocins originate from lactic acid bacteria, which have recently been modified by scientists. Many strains of lactic acid bacteria related to food groups could produce bacteriocins or antibacterial proteins highly effective against foodborne pathogens such as Staphylococcus aureus, Pseudomonas fluorescens, P. aeruginosa, Salmonella typhi, Shigella flexneri, Listeria monocytogenes, Escherichia coli O157:H7, and Clostridium botulinum. A wide range of bacteria belonging primarily to the genera Bifidobacterium and Lactobacillus have been characterized with different health‐promoting attributes. Extensive studies and in‐depth understanding of these antimicrobials mechanisms of action could enable scientists to determine their production in specific probiotic lactic acid bacteria, as they are potentially crucial for the final preservation of functional foods or for medicinal applications. In this review study, the structure, classification, mode of operation, safety, and antibacterial properties of bacteriocins as well as their effect on foodborne pathogens and antibiotic‐resistant bacteria were extensively studied.

Therapeutic and Improving Function of Lactobacilli in the Prevention and Treatment of Cardiovascular-Related Diseases: A Novel Perspective From Gut Microbiota

The occurrence and development of cardiovascular-related diseases are associated with structural and functional changes in gut microbiota (GM). The accumulation of beneficial gut commensals contributes to the improvement of cardiovascular-related diseases. The cardiovascular-related diseases that can be relieved by Lactobacillus supplementation, including hypercholesterolemia, atherosclerosis, myocardial infarction, heart failure, type 2 diabetes mellitus, and obesity, have expanded. As probiotics, lactobacilli occupy a substantial part of the GM and play important functional roles through various GM-derived metabolites. Lactobacilli ultimately have a beneficial impact on lipid metabolism, inflammatory factors, and oxidative stress to relieve the symptoms of cardiovascular-related diseases. However, the axis and cellular process of gut commensal Lactobacillus in improving cardiovascular-related diseases have not been fully elucidated. Additionally, Lactobacillus strains produce diverse antimicrobial peptides, which help maintain intestinal homeostasis and ameliorate cardiovascular-related diseases. These strains are a field that needs to be further investigated immediately. Thus, this review demonstrated the mechanisms and summarized the evidence of the benefit of Lactobacillus strain supplementation from animal studies and human clinical trials. We also highlighted a broad range of lactobacilli candidates with therapeutic capability by mining their metabolites. Our study provides instruction in the development of lactobacilli as a functional food to improve cardiovascular-related diseases.

Mining, heterologous expression, purification, antibactericidal mechanism, and application of bacteriocins: A review

Bacteriocins are generally considered as low-molecular-weight ribosomal peptides or proteins synthesized by G⁺ and G^- bacteria that inhibit or kill other related or unrelated microorganisms. However, low yield is an important factor restricting the application of bacteriocins. This paper reviews mining methods, heterologous expression in different systems, the purification technologies applied to bacteriocins, and identification methods, as well as the antibacterial mechanism and applications in three different food systems. Bioinformatics improves the efficiency of bacteriocins mining. Bacteriocins can be heterologously expressed in different expression systems (e.g., Escherichia coli, Lactobacillus, and yeast). Ammonium sulfate precipitation, dialysis membrane, pH-mediated cell adsorption/desorption, solvent extraction, macroporous resin column, and chromatography are always used as purification methods for bacteriocins. The bacteriocins are identified through electrophoresis and mass spectrum. Cell envelope (e.g., cell permeabilization and pore formation) and inhibition of gene expression are common antibacterial mechanisms of bacteriocins. Bacteriocins can be added to protect meat products (e.g., beef and sausages), dairy products (e.g., cheese, milk, and yogurt), and vegetables and fruits (e.g., salad, apple juice, and soybean sprouts). The future research directions are also prospected.

Bacteriocin PJ4 from probiotic lactobacillus reduced adipokine and inflammasome in high fat diet induced obesity

One of the characteristic features of obesity is increased body weight and accumulation of adipose tissue. It is associated with low grade inflammation and gut dysbiosis. Probiotics and its products could be an ideal strategy to prevent or treat diabetes. In the present study, animals were induced obesity by providing them with high fat diet. Three purified bacteriocins i.e., DT24, PJ4 and TSU4, previously isolated and purified from various probiotic strains, were given as treatment strategies, following the induction of obesity. Upon the completion of the study, animals were sacrificed and were checked for their tissue expression of inflammatory mediators and adipokines. Serum hormone and cytokines analysis were performed to check their inflammatory state. Treatment with purified bacteriocin DT24 did not show any therapeutic effect in any of the parameter studied. Bacteriocin TSU4 on the other hand showed better reversal compared to DT24. Bacteriocin PJ4 showed the most promising results by reversing all the altered parameters significantly. It significantly reversed all the biochemical, immunological in terms of serum cytokines as well as altered morphological characteristics. PJ4 can be further explored to determine its mode of action. The anti-microbial proteins or to be more specific, bacteriocins, which shows broad spectrum efficacy, could be a better alternative in modulating gut microflora for the treatment of obesity and diabetes characteristics. The efficacy of bacteriocin PJ4 may also be due to the source of the host of Lactobacillus.

Scientific Opinion on the update of the list of QPS-recommended biological agents intentionally added to food or feed as notified to EFSA (2017-2019)

The qualified presumption of safety (QPS) was developed to provide a safety pre-assessment within EFSA for microorganisms. Strains belonging to QPS taxonomic units (TUs) still require an assessment based on a specific data package, but QPS status facilitates fast track evaluation. QPS TUs are unambiguously defined biological agents assessed for the body of knowledge, their safety and their end use. Safety concerns are, where possible, to be confirmed at strain or product level, and reflected as 'qualifications'. Qualifications need to be evaluated at strain level by the respective EFSA units. The lowest QPS TU is the species level for bacteria, yeasts and protists/algae, and the family for viruses. The QPS concept is also applicable to genetically modified microorganisms used for production purposes if the recipient strain qualifies for the QPS status, and if the genetic modification does not indicate a concern. Based on the actual body of knowledge and/or an ambiguous taxonomic position, the following TUs were excluded from the QPS assessment: filamentous fungi, oomycetes, streptomycetes, Enterococcus faecium, Escherichia coli and bacteriophages. The list of QPS-recommended biological agents was reviewed and updated in the current opinion and therefore now becomes the valid list. For this update, reports on the safety of previously assessed microorganisms, including bacteria, yeasts and viruses (the latter only when used for plant protection purposes) were reviewed, following an Extensive Literature Search strategy. All TUs previously recommended for 2016 QPS list had their status reconfirmed as well as their qualifications. The TUs related to the new notifications received since the 2016 QPS opinion was periodically evaluated for QPS status in the Statements of the BIOHAZ Panel, and the QPS list was also periodically updated. In total, 14 new TUs received a QPS status between 2017 and 2019: three yeasts, eight bacteria and three algae/protists.

Purification, characterization and mode of action of enterocin, a novel bacteriocin produced by Enterococcus faecium TJUQ1

Enterococcus faecium TJUQ1 with high bacteriocin-producing ability was isolated from pickled Chinese celery. In this study, enterocin TJUQ1 was purified by ammonium sulfate precipitation, reversed-phase chromatography (Sep-Pak C₈) and cation-exchange chromatography. The activity of the purified bacteriocin was 44,566.41 ± 874.69 AU/mg, which corresponds to a purification fold of 35.89 ± 2.34. The molecular mass was 5520 Da by MALDI-TOF MS and Tris-Tricine SDS-PAGE. The result of LC-MS/MS showed that the bacteriocin shared 59.15% identity with enterocin produced by E. faecium GN (accession no. O34071). PCR amplification revealed that E. faecium TJUQ1 possesses a gene encoding enterocin B with 60% identity to enterocin B. Circular dichroism (CD) spectroscopy showed that the molecular conformation was 32.6% helix, 19.5% beta, 12.9% turn and 35.0% random. The stability of enterocin TJUQ1 was measured. After exposure at 121 °C for 15 min, the residual antimicrobial activity of enterocin TJUQ1 was 85.95 ± 1.32%. The antimicrobial activity of enterocin TJUQ1 was still active over a pH range of 3-11. Enterocin TJUQ1 was inactivated after exposure to proteolytic enzymes but was not inactivated by lipase or amylase. These results showed that enterocin TJUQ1 was a novel class II bacteriocin. Enterocin TJUQ1 showed wide antibacterial activity against food-borne gram-negative and gram-positive pathogens, such as Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Salmonella enterica. The MIC was 5.26 ± 0.24 μg/mL against L. monocytogenes CMCC 1595. SEM and TEM were used to observe the changes in the morphological and intracellular organization of L. monocytogenes CMCC 1595 cells treated with enterocin TJUQ1. The results demonstrated that enterocin TJUQ1 increased extracellular electrical conductivity, facilitated pore formation, triggered the release of UV-absorbing materials, ATP and LDH, and even caused cell lysis in L. monocytogenes CMCC 1595 cells. Based on the characterization, the wide inhibitory spectrum and mode of action determined so far, enterocin TJUQ1 is a potential preservative for the food industry.

Molecular Characterization and Heterologous Production of the Bacteriocin Peocin, a DNA Starvation/Stationary Phase Protection Protein, from Paenibacillus ehimensis NPUST1

The production of a bacteriocin-like substance with antimicrobial activity, named peocin, by the probiotic Paenibacillus ehimensis NPUST1 was previously reported by our laboratory. The present study aimed to identify peocin and increase the peocin yield by heterologous expression in Escherichia coli BL21(DE3). Peocin was identified as a DNA starvation/stationary phase protection protein, also called DNA-binding protein from starved cells (Dps), by gel overlay and LC-MS/MS analysis. For mass production of peocin, fed-batch cultivation of E. coli was performed using a pH-stat control system. Purification by simple nickel affinity chromatography and dialysis yielded 45.3 mg of purified peocin from a 20-mL fed-batch culture (49.3% recovery). The biological activity of the purified peocin was confirmed by determination of the MIC and MBC against diverse pathogens. Purified peocin exhibited antimicrobial activity against aquatic, food spoilage, clinical and antibiotic-resistant pathogens. In an in vivo challenge test, zebrafish treated with purified peocin exhibited significantly increased survival rates after A. hydrophila challenge. The present study is the first to show the antimicrobial activity of Dps and provides an efficient strategy for production of bioactive peocin, which will aid the development of peocin as a novel antimicrobial agent with potential applications in diverse industries.

Heterologous expression and purification of BtCspB, a novel cold-shock protein-like bacteriocin from Bacillus thuringiensis BRC-ZYR2

A novel Bacillus thuringiensis (Bt) bacteriocin BtCspB, active against a food-borne pathogen Bacillus cereus, was identified and purified by a traditional four-step chromatographic process with low yield (44.5 µg/L) in our lab previously. The aim of this study was to dramatically increase its yield by heterologous expression of BtCspB. The BtCspB gene from Bt BRC-ZYR2 was successfully heterologously expressed in Escherichia coli BL21 (DE3). Affinity chromatography was used to obtain the pure BtCspB up to 20 mg/L. The purified BtCspB showed a MIC value of 12.5 µg/mL and a MBC value of 50.0 µg/mL against Bacillus cereus ATCC 10987. The bacteriocin activity of BtCspB against B. cereus ATCC 10987 was further directly detected in a gel-overlay assay. The anti-B. cereus activity, however, was lower than the bacteriocin purified by the traditional four-step chromatographic process probably because of structural modifications. Compared with the traditional method, the yield of the bacteriocin by heterologous expression increased by 449 times, and the purification step was dramatically simplified, which laying a foundation for the industrial production of this novel cold-shock protein-like bacteriocin BtCspB active against B. cereus.

In Vivo Assessment of Immunogenicity and Toxicity of the Bacteriocin TSU4 in BALB/c Mice

Bacteriocin TSU4 is a novel antimicrobial peptide isolated from Catla catla gut isolate Lactobacillus animalis TSU4. It has been reported for its potential antimicrobial activity against fish pathogens and food spoilage bacteria. In vivo safety evaluation is necessary to determine its immunogenicity, toxicity, and importance in real-life applications. The present study was designed to evaluate the immunogenicity, acute and sub-chronic toxicity of bacteriocin TSU4 in BALB/c mice to ensure its safety in industrial application. Male BALB/c mice were administered intraperitoneally for immunogenicity assessment, by oral gavage with 50, 100, and 200 mg/kg/body weight for acute test and 0.5 mg/kg/day dose of bacteriocin TSU4 for sub-chronic toxicity test. Neither mortality nor any infections were observed during experimental period. There was no major increase in antibody titer during the immunogenicity test, and no mortality was observed during acute or sub-chronic toxicity tests. The LD₅₀ value of bacteriocin TSU4 was found to be higher than 200 ± 0.45 mg/kg. No significant change in the serum biochemical markers, histopathological analysis and visual observation in spleen sizes was observed. These findings revealed that bacteriocin TSU4 is a non-immunogenic, safe, non-toxic, and could be a potential candidate for industrial applications in food preservation and aquaculture industries.

Potential of bacteriocins produced by probiotic bacteria isolated from tiger shrimp and prawns as antibacterial to Vibrio, Pseudomonas, and Aeromonas species on fish

Backgrounds: Bacteriocin has been used widely in industry as a biopreservative agent. The objective of the present study was to investigate the potency of Bacteriocin isolated from tiger prawn Penaeus monodon and freshwater shrimp Macrobrachium rosenbergii as an anti-bacterial on fish. Methods: A total of ten candidates of probiotic bacteria consisted of five isolates from tiger shrimps (H1, H2, H3, H4, H5) and five isolates from freshwater prawns (W1, W2, W3, W4, W5) were evaluated. Bacteriocin wasBacteriocin was produced by centrifugation at a speed of 150 rpm and at 37 °C for 24 hours. The bacteriocin extract was purified by adding sulphate ammonium salt {(NH4) 2SO4} at 80% of the saturation level. Bacteriocin activity was determined using a diffusion method against pathogenic bacteria Vibrio alginolyticus, Aeromonas hydrophillaAeromonas hydrophilla and Pseudomonas stutzeri. Bacteriocins were analyzed usinganalyzedusing High Performance Liquid Chromatography (HPLC) and Fourier Transform Infra-Red (FTIR). The data were subjected to analysis of variance (ANOVA) and followed with Duncans multiple range test. Results: Bacteriocins produced by bacteria isolate H4 from tiger prawn indicated the highest bacteriocin activity againstbacteriocin activity against Pseudomonas stutzeri at stutzeri at the diameter of inhibition zone of 887.10 ± 409.24 mm 2/mL. While isolate W2 from freshwater shrimp indicated inhibition zone of 1466.96 ± 127.62 mm 2/mL. Both bacteriocins were purified by chromatography column using Sephadex LH-20. Conclusions: This finding showed that bacterial isolates H4 and W2 have the potential to produce bacteriocins which inhibit the pathogenic bacteria. FTIR analysis showed an amide group at wave number 1652cm -1 contained in the bacteriocins of isolates H4 and W2.

Update of the list of QPS-recommended biological agents intentionally added to food or feed as notified to EFSA 6: suitability of taxonomic units notified to EFSA until March 2017

The qualified presumption of safety (QPS) concept was developed to provide a harmonised generic pre‐evaluation to support safety risk assessments of biological agents performed by EFSA's scientific Panels. The identity, body of knowledge, safety concerns and antimicrobial resistance of valid taxonomic units were assessed. Safety concerns identified for a taxonomic unit are, where possible and reasonable in number, reflected as ‘qualifications’ which should be assessed at the strain level by the EFSA's scientific Panels. No new information was found that would change the previously recommended QPS taxonomic units and their qualifications. Between the end of September 2016 and March 2017, the QPS notification list was updated with 87 applications for market authorisation. From these, 32 biological agents already had a QPS status, and 37 were not included in the evaluation as they are filamentous fungi or enterococci. Streptomyces species (Streptomyces cinnamonensis, Streptomyces mobaraensis and Streptomyces violaceoruber), Bacillus circulans (three notifications) and Escherichia coli (seven notifications) were re‐confirmed not suitable for QPS. Streptomyces rubiginosus and Streptomyces netropsis, not evaluated within the previous mandate, were also not recommended for QPS. Streptomyces spp. and E. coli will be excluded from further QPS evaluations within the current QPS mandate. Hyphomicrobium denitrificans, which has never been evaluated before, was not recommended for the QPS list and for Pseudomonas amyloderamosa, the QPS assessment was not applicable because it is not a validated species. Lactobacillus animalis was a new taxonomic unit recommended to have the QPS status.

Phospholipid/Polydiacetylene Vesicle-Based Colorimetric Assay for High-Throughput Screening of Bacteriocins and Halocins

The colorimetric assay is phospholipid/polydiacetylene vesicle-based assay used for the detection of membrane-acting peptides. Bacteriocins and halocins are antimicrobial peptides known to kill target cells by membrane disruption. Therefore, the assay was applied for high-throughput (HTP) screening of bacteriocins and halocins produced by lactic acid bacteria and haloarchaea, respectively. The assay consisted of vesicles which were synthesized using four different phospholipids: dipalmitoylphosphatydilcholine (DPPC), dimyristoylphosphatidylcholine (DMPC), dimyristoylphosphoethanolamine (DMPE) and dimyristoylphosphatidylglycerol (DMPG) in combination with diacetylene monomer 10,12-tricosadiy noic acid (TRCDA). These vesicles demonstrated blue colour at 640 nm and turned pink/red after interaction with nisin. DMPE/TRCDA vesicles showed pink colour with the highest colorimetric response (CR %) after treatment with nisin and, therefore, selected for the screening of bacteriocins and halocins. The colour of the vesicles was changed within 5 min in the presence of 5 μM nisin suggesting the sensitivity of assay. The assay was applied on 54 strains of lactic acid bacteria (LAB) and 53 haloarchaea for screening of bacteriocins and halocins, respectively. Out of these strains, three strains of LAB and five strains of haloarchaea were found to be bacteriocin and halocin non-producer, respectively. The other strains demonstrated the presence of bacteriocins and halocins. The colorimetric assay was found to be rapid, specific and reliable for HTP screening of antimicrobial peptides such as bacteriocins and halocins from producer strains isolated from various natural resources.

Determination of Acquired Resistance Profiles of Pseudomonas aeruginosa Isolates and Characterization of an Effective Bacteriocin-Like Inhibitory Substance (BLIS) Against These Isolates

Background

The emergence of pan-drug resistant strains (PDR) of Pseudomonas aeruginosa has led to renewed efforts to identify alternative agents, such as bacteriocins and bacteriocin-like inhibitory substances (BLISs).

Objectives

The aims of this study were to determine the acquired resistance profiles of multidrug-resistant (MDR), extensively drug-resistant (XDR), and PDR P. aeruginosa isolates based on the revised definitions of the CDC and ECDC and to screen and characterize effective BLISs against these isolates.

Patients and Materials

In a cross-sectional study, 96 P. aeruginosa strains were isolated during a 12-month period. The resistance profiles of these isolates were determined as MDR, XDR, and PDR, and the data were analyzed using WHONET5.6 software. A BLIS against the P. aeruginosa strains was characterized based on its physicochemical properties, size, growth curves, and production profiles.

Results

Among the 96 isolates of P. aeruginosa, 2 (2.1%), 94 (97.9%), and 63 (65.6%) were non-MDR, MDR, and XDR, respectively, and 1 (1.1%) was PDR. The most effective antibiotics against these isolates were polymyxins and fosfomycin. A BLIS isolated from the P. aeruginosa DSH22 strain had potent activity against 92 (95.8%) of the 96 isolates. The BLIS was heat stable, (up to 100°C for 10 min), UV stable, and active within a pH range of 3 - 9. The activity of BLIS disappeared when treated with trypsin, proteinase K, and pepsin, indicating its proteinous nature. Based on its size (25 kDa), the BLIS may belong to the large colicin-like bacteriocin family. BLIS production started in the midexponential phase of growth, and the maximum level (2700 AU/mL) occurred in the late-stationary phase after 25 hours of incubation at 30°C.

Conclusions

This BLIS with broad-spectrum activity may be a potential agent for the treatment or control of drug-resistant strains of P. aeruginosa infection.

Purification, Characterization, and Optimum Conditions of Fermencin SD11, a Bacteriocin Produced by Human Orally Lactobacillus fermentum SD11

Fermencin SD11, a bacteriocin produced by human orally Lactobacillus fermentum SD11, was purified, characterized, and optimized in conditions for bacterial growth and bacteriocin production. Fermencin SD11 was purified using three steps of ammonium sulfate precipitation, gel filtration chromatography, and reverse-phase high-performance liquid chromatography. The molecular weight was found to be 33,000 Da using SDS-PAGE and confirmed as 33,593.4 Da by liquid chromatography-mass spectrometry. Fermencin SD11 exhibited activity against a wide range of oral pathogens including cariogenic and periodontogenic pathogens and Candida. The active activity was stable between 60 - 80 °C in a pH range of 3.0 to 7.0. It was sensitive to proteolytic enzymes (proteinase K and trypsin), but it was not affected by α-amylase, catalase, lysozyme, and saliva. The optimum conditions for growth and bacteriocin production of L. fermentum SD11 were cultured at acidic with pH of 5.0-6.0 at 37 or 40 °C under aerobic or anaerobic conditions for 12 h. It is promising that L. fermentum SD11 and its bacteriocin may be an alternative approach for promoting oral health or prevention of oral diseases, e.g., dental caries and periodontitis, which would require further clinical trials.