Effect of bacteriocin and exopolysaccharides isolated from probiotic on P. aeruginosa PAO1 biofilm

The inhibition mechanism of co-cultured probiotics on biofilm formation of Klebsiella pneumoniae

AIMS

Klebsiella pneumoniae, an important opportunistic pathogen of nosocomial inflection, is known for its ability to form biofilm. The purpose of the current study is to assess how co- or mono-cultured probiotics affect K. pneumoniae's ability to produce biofilms and investigate the potential mechanisms by using a polyester nonwoven chemostat and a Caco-2 cell line.

METHODS AND RESULTS

Compared with pure cultures of Lactobacillus rhamnosus and Lactobacillus sake, the formation of K. pneumoniae biofilm was remarkably inhibited by the mixture of L. rhamnosus, L. sake, and Bacillus subtilis at a ratio of 5:5:1 by means of qPCR and FISH assays. In addition, Lactobacillus in combination with B. subtilis could considerably reduce the adherence of K. pneumoniae to Caco-2 cells by using inhibition, competition, and displacement assays. According to the RT-PCR assay, the adsorption of K. pneumoniae to Caco-2 cells was effectively inhibited by the co-cultured probiotics, leading to significant reduction in the expression of proinflammatory cytokines induced by K. pneumoniae. Furthermore, the HPLC and RT-PCR analyses showed that the co-cultured probiotics were able to successfully prevent the expression of the biofilm-related genes of K. pneumoniae by secreting plenty of organic acids as well as the second signal molecule (c-di-GMP), resulting in inhibition on biofilm formation.

CONCLUSION

Co-culture of L. sake, L. rhamnosus, and B. subtilis at a ratio of 5:5:1 could exert an antagonistic effect on the colonization of pathogenic K. pneumoniae by down-regulating the expression of biofilm-related genes. At the same time, the co-cultured probiotics could effectively inhibit the adhesion of K. pneumoniae to Caco-2 cells and block the expression of proinflammatory cytokines induced by K. pneumoniae.

Elimination of Pathogen Biofilms via Postbiotics from Lactic Acid Bacteria: A Promising Method in Food and Biomedicine

Pathogenic biofilms provide a naturally favorable barrier for microbial growth and are closely related to the virulence of pathogens. Postbiotics from lactic acid bacteria (LAB) are secondary metabolites and cellular components obtained by inactivation of fermentation broth; they have a certain inhibitory effect on all stages of pathogen biofilms. Postbiotics from LAB have drawn attention because of their high stability, safety dose parameters, and long storage period, which give them a broad application prospect in the fields of food and medicine. The mechanisms of eliminating pathogen biofilms via postbiotics from LAB mainly affect the surface adhesion, self-aggregation, virulence, and QS of pathogens influencing interspecific and intraspecific communication. However, there are some factors (preparation process and lack of target) which can limit the antibiofilm impact of postbiotics. Therefore, by using a delivery carrier and optimizing process parameters, the effect of interfering factors can be eliminated. This review summarizes the concept and characteristics of postbiotics from LAB, focusing on their preparation technology and antibiofilm effect, and the applications and limitations of postbiotics in food processing and clinical treatment are also discussed.

Restraining Staphylococcus aureus Virulence Factors and Quorum Sensing through Lactic Acid Bacteria Supernatant Extracts

The escalating prevalence of antibiotic-resistant bacteria poses a grave threat to human health, necessitating the exploration of novel alternatives to conventional antibiotics. This study investigated the impact of extracts derived from the supernatant of four lactic acid bacteria strains on factors contributing to the pathogenicity of three Staphylococcus aureus strains. The study evaluated the influence of lactic acid bacteria supernatant extracts on the growth, biofilm biomass formation, biofilm metabolic activity, and biofilm integrity of the S. aureus strains. Additionally, the impact on virulence factors (hemolysin and coagulase) was examined. Gas chromatography coupled with mass spectrometry was used to identify the bioactive compounds in the extracts, while molecular docking analyses explored potential interactions. Predominantly, the extracts contain eight 2,5-diketopiperazines, which are cyclic forms of peptides. The extracts demonstrated inhibitory effects on biofilm formation, the ability to disrupt mature biofilms, and reduce the biofilm cell metabolic activity of the S. aureus strains. Furthermore, they exhibited the ability to inhibit α-hemolysin production and reduce coagulase activity. An in silico docking analysis reveals promising interactions between 2,5-diketopiperazines and key proteins (SarA and AgrA) in S. aureus, confirming their antivirulence and antibiofilm activities. These findings suggest that 2,5-diketopiperazines could serve as a promising lead compound in the fight against antibiotic-resistant S. aureus.

Molecular Aspects of the Functioning of Pathogenic Bacteria Biofilm Based on Quorum Sensing (QS) Signal-Response System and Innovative Non-Antibiotic Strategies for Their Elimination

One of the key mechanisms enabling bacterial cells to create biofilms and regulate crucial life functions in a global and highly synchronized way is a bacterial communication system called quorum sensing (QS). QS is a bacterial cell-to-cell communication process that depends on the bacterial population density and is mediated by small signalling molecules called autoinducers (AIs). In bacteria, QS controls the biofilm formation through the global regulation of gene expression involved in the extracellular polymeric matrix (EPS) synthesis, virulence factor production, stress tolerance and metabolic adaptation. Forming biofilm is one of the crucial mechanisms of bacterial antimicrobial resistance (AMR). A common feature of human pathogens is the ability to form biofilm, which poses a serious medical issue due to their high susceptibility to traditional antibiotics. Because QS is associated with virulence and biofilm formation, there is a belief that inhibition of QS activity called quorum quenching (QQ) may provide alternative therapeutic methods for treating microbial infections. This review summarises recent progress in biofilm research, focusing on the mechanisms by which biofilms, especially those formed by pathogenic bacteria, become resistant to antibiotic treatment. Subsequently, a potential alternative approach to QS inhibition highlighting innovative non-antibiotic strategies to control AMR and biofilm formation of pathogenic bacteria has been discussed.

Exopolysaccharides of lactic acid bacteria: Structure, biological activity, structure-activity relationship, and application in the food industry: A review

Over the past few decades, researchers have discovered that probiotics play an important role in our daily lives. With the further deepening of research, more and more evidence show that bacterial metabolites have an important role in food and human health, which opens up a new direction for the research of lactic acid bacteria (LAB) in the food and pharmaceutical industry. Many LAB have been widely studied because of the ability of exopolysaccharides (EPS). Lactic acid bacteria exopolysaccharides (LAB EPS) not only have great potential in the treatment of human diseases but also can become natural ingredients in the food industry to provide special qualitative structure and flavor. This paper has organized and summarized the biosynthesis, strain selection, production process parameters, structure, and biological activity of LAB EPS, filling in the monotony and incompleteness of previous articles' descriptions of LAB EPS. Therefore, this paper focuses on the general biosynthetic pathway, structural characterization, structure-activity relationship, biological activity of LAB EPS, and their application in the food industry, which will help to deepen people's understanding of LAB EPS and develop new active drugs from LAB EPS. Although the research results are relatively affluent, the low yield, complex structure, and few clinical trials of EPS are still the reasons that hinder its development. Therefore, future knowledge expansion should focus on the regulation of structure, physicochemical properties, function, higher production of EPS, and clinical trial applications, which can further increase the commercial significance and value of EPS. Furthermore, better understanding the structure-function relationship of EPS in food remains a challenge to date.

Selected strategies to fight pathogenic bacteria

Natural products and analogues are a source of antibacterial drug discovery. Considering drug resistance levels emerging for antibiotics, identification of bacterial metalloenzymes and the synthesis of selective inhibitors are interesting for antibacterial agent development. Peptide nucleic acids are attractive antisense and antigene agents representing a novel strategy to target pathogens due to their unique mechanism of action. Antisense inhibition and development of antisense peptide nucleic acids is a new approach to antibacterial agents. Due to the increased resistance of biofilms to antibiotics, alternative therapeutic options are necessary. To develop antimicrobial strategies, optimised in vitro and in vivo models are needed. In vivo models to study biofilm-related respiratory infections, device-related infections: ventilator-associated pneumonia, tissue-related infections: chronic infection models based on alginate or agar beads, methods to battle biofilm-related infections are discussed. Drug delivery in case of antibacterials often is a serious issue therefore this review includes overview of drug delivery nanosystems.

Antibiofilm and antimicrobial activity of Lactobacillus cell free supernatant against Pseudomonas aeruginosa isolated from burn wounds

The present study investigated the antimicrobial and anti-biofilm effects of indigenous Lactobacillus probiotic strains on Pseudomonas aeruginosa isolated from burn wound infection in laboratory conditions. The effect of 7 probiotic strains isolated from infant faeces on the pathogenicity factors of P. aeruginosa, including protease, elastase, antibiofilm and antipyocyanin was measured. Also, diffusion methods in the well and micro broth dilution were used to evaluate the antimicrobial activity of probiotics. All tests were performed in triplicate. A negative control and a positive control were used for each test. SPSS version 22 software was used for statistical analysis, and a p < 0.05 was considered statistically significant. A total of 30 clinical isolates of P. aeruginosa were isolated. The elastolytic activity of P. aeruginosa isolates decreased after adding Cell free supernatant (CFS) of each Lactobacillus. L1, L4, L5, and L6 strains had a 100% inhibitory effect on pathogen isolates. L3 and L7 strains had the lowest inhibitory effect. The inhibitory effect of CFS extracted from lactobacilli on protease production by P. aeruginosa. L1, L4, L5, and L6 strains had an inhibitory effect on all tested isolates. L2, L3, and L7 strains had a less inhibitory effect. L4 strain had the highest inhibitory effect on pyocyanin production by P. aeruginosa (50%), followed by L5 (43.3%), L1 (40%), and L6 (23.3%) strains. L3 and L7 strains had no inhibitory effect on the pyocyanin production of P. aeruginosa isolates. It was found that the CFS of 4 isolates (L1, L4, L5, and L6) was the most active extract and had a 100% inhibitory effect against biofilm formation of all P. aeruginosa strains. The L3 strain had the least inhibitory effect against the biofilm formation of pathogens. Overall, this study showed that probiotics could be promising alternatives to combat the pathogenicity of P. aeruginosa in burn wounds.

Topical application of Lactobacilli successfully eradicates Pseudomonas aeruginosa biofilms and promotes wound healing in chronic wounds

Chronic wounds are difficult to treat due to the presence of biofilm which prevents wound healing. Pseudomonas aeruginosa is one of the most common pathogens found in chronic wounds and conventional treatment strategies have been ineffective in the eradication of its biofilm, without harming the surrounding healthy tissue at the same time. Here, we introduced an innovative approach applying the probiotic product Bio-K+ (containing three lactobacilli) topically as an antimicrobial and antibiofilm agent. We identified lactic acid as the main active component. While antibiotics and antiseptics such as silver-ions only demonstrated limited efficacy, Bio-K+ was able to completely eradicate mature P. aeruginosa biofilms established in an in-vitro and ex-vivo human skin model. Furthermore, it demonstrated biocompatibility in the co-culture with human dermal fibroblasts and accelerated the migration of fibroblasts in a cell migration assay promoting wound healing. To enhance clinical practicability, we introduced Bio-K+ into the hydrocolloid dressing Aquacel, achieving sustained release of lactic acid and biofilm eradication. This new treatment approach applying probiotics could represent a major improvement in the management of chronic wounds and can be extended in treating other biofilm-associated infections.

Optimization of starch extraction from Amorphophallus paeoniifolius corms using response surface methodology (RSM) and artificial neural network (ANN) for improving yield with tenable chemical attributes

The development of the extraction process for improving the starch yield from unconventional plants is emerging as a topic of interest. In this respect, the present work aimed to optimize the starch extraction from the corms of elephant foot yam (Amorphophallus paeoniifolius) with the help of response surface methodology (RSM) and artificial neural network (ANN). The RSM model performed better than the ANN in predicting the starch yield with higher precision. In this connection, this study for the first time reports the significant improvement of starch yield from A. paeoniifolius (51.76 g/100 g of the corm dry weight). The extracted starch samples based on yield - high (APHS), medium (APMS), and low (APLS) exhibited a variable granule size (7.17-14.14 μm) along with low ash content, moisture content, protein, and free amino acid indicating purity and desirability. The FTIR analysis also confirmed the chemical composition and purity of the starch samples. Moreover, the XRD analysis showed the prevalence of C-type starch (2θ = 14.303°). Based on other physicochemical, biochemical, functional, and pasting properties, the three starch samples showed more or less similar characteristics thereby indicating the sustentation of beneficial attributes of starch molecules irrespective of the variation in extraction parameters.

Implication of Obesity and Gut Microbiome Dysbiosis in the Etiology of Colorectal Cancer

The complexity and variety of gut microbiomes within and among individuals have been extensively studied in recent years in connection to human health and diseases. Our growing understanding of the bidirectional communication between metabolic diseases and the gut microbiome has also highlighted the significance of gut microbiome dysbiosis in the genesis and development of obesity-related cancers. Therefore, it is crucial to comprehend the possible role of the gut microbiota in the crosstalk between obesity and colorectal cancer (CRC). Through the induction of gut microbial dysbiosis, gut epithelial barrier impairment, metabolomic dysregulation, chronic inflammation, or dysregulation in energy harvesting, obesity may promote the development of colorectal tumors. It is well known that strategies for cancer prevention and treatment are most effective when combined with a healthy diet, physical activity, and active lifestyle choices. Recent studies also suggest that an improved understanding of the complex linkages between the gut microbiome and various cancers as well as metabolic diseases can potentially improve cancer treatments and overall outcomes. In this context, we herein review and summarize the clinical and experimental evidence supporting the functional role of the gut microbiome in the pathogenesis and progression of CRC concerning obesity and its metabolic correlates, which may pave the way for the development of novel prognostic tools for CRC prevention. Therapeutic approaches for restoring the microbiome homeostasis in conjunction with cancer treatments are also discussed herein.

Exopolysaccharides from vaginal lactobacilli modulate microbial biofilms

BACKGROUND

Exopolysaccharides (EPS) secreted by beneficial lactobacilli exert a plethora of positive activities, but little is known about their effects on biofilms of opportunistic vaginal pathogens and especially on biofilms of lactobacilli themselves. Here, the EPS produced by six vaginal lactobacilli, belonging to Lactobacillus crispatus (BC1, BC4, BC5) and Lactobacillus gasseri (BC9, BC12, BC14) species were isolated from cultural supernatants and lyophilized.

RESULTS

Lactobacillus EPS were chemically characterized in terms of monosaccharide composition by liquid chromatography (LC) analysis coupled to UV and mass spectrometry (MS) detection. Moreover, the ability of EPS (0.1, 0.5, 1 mg/mL) to stimulate the biofilm formation of lactobacilli and to inhibit the formation of pathogens' biofilms was evaluated by crystal violet (CV) staining and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Isolated EPS (yields 133-426 mg/L) were heteropolysaccharides mainly composed of D-mannose (40-52%) and D-glucose (11-30%). For the first time we demonstrated that Lactobacillus EPS were able to stimulate in a dose-dependent manner (p < 0.05) the formation of biofilms of ten strains belonging to L. crispatus, L. gasseri and Limosilactobacillus vaginalis species, in terms of cell viability (84-282% increase at 1 mg/mL) and especially biofilm biomass (40-195% increase at 1 mg/mL), quantified with MTT assay and CV staining, respectively. EPS released from L. crispatus and L. gasseri were found to better stimulate the biofilms of the same producer species rather than that of other species, including producing strains themselves and other strains. Conversely, the biofilm formation of bacterial (Escherichia coli, Staphylococcus spp., Enterococcus spp. and Streptococcus agalactiae) and fungal (Candida spp.) pathogens was inhibited. The anti-biofilm activity was dose-dependent and was more marked for L. gasseri-derived EPS (inhibition up to 86%, 70%, and 58% at 1 mg/mL, 0.5 mg/mL, and 0.1 mg/mL, respectively), whilst L. crispatus-derived EPS resulted overall less efficient (inhibition up to 58% at 1 mg/mL and 40% at 0.5 mg/mL) (p < 0.05).

CONCLUSIONS

Lactobacilli-derived EPS favour the biofilm formation of lactobacilli preventing, at the same time, that of opportunistic pathogens. These results support the possible employment of EPS as postbiotics in medicine as a therapeutic/preventive strategy to counteract vaginal infections.

Antibiofilm activity and NMR-based metabolomic characterization of cell-free supernatant of Limosilactobacillus reuteri DSM 17938

The microbial biofilm has been defined as a "key virulence factor" for a multitude of microorganisms associated with chronic infections. Its multifactorial nature and variability, as well as an increase in antimicrobial resistance, suggest the need to identify new compounds as alternatives to the commonly used antimicrobials. The aim of this study was to assess the antibiofilm activity of cell-free supernatant (CFS) and its sub-fractions (SurE 10 K with a molecular weight <10 kDa and SurE with a molecular weight <30 kDa), produced by Limosilactobacillus reuteri DSM 17938, vs. biofilm-producing bacterial species. The minimum inhibitory biofilm concentration (MBIC) and the minimum biofilm eradication concentration (MBEC) were determined via three different methods and an NMR metabolomic analysis of CFS and SurE 10K was performed to identify and quantify several compounds. Finally, the storage stability of these postbiotics was evaluated by a colorimetric assay by analyzing changes in the CIEL*a*b parameters. The CFS showed a promising antibiofilm activity against the biofilm developed by clinically relevant microorganisms. The NMR of CFS and SurE 10K identifies and quantifies several compounds, mainly organic acids and amino acids, with lactate being the most abundant metabolite in all the analyzed samples. The CFS and SurE 10 K were characterized by a similar qualitative profile, with the exception of formate and glycine detected only in the CFS. Finally, the CIEL*a*b parameters assess the better conditions to analyze and use these matrices for the correct preservation of bioactive compounds.

Antimicrobial activity against Staphylococcus aureus and genome features of Lactiplantibacillus plantarum LR-14 from Sichuan pickles

The persistence of Staphylococcus aureus within biofilm can lead to contamination of medical devices and life-threatening infections. Luckily, lactic acid bacteria (LAB) have an inhibitory effect on the growth of these bacteria. This study aims to select LAB strains from fermented vegetables, and analyze their potential inhibition activities against S. aureus. In total, 45 isolates of LAB were successfully isolated from Sichuan pickles, and the CFS of Lactiplantibacillus plantarum LR-14 exerted the strongest inhibitory effect against S. aureus. Moreover, S. aureus cells in planktonic and biofilm states both wrinkled and damaged when treated with the CFS of L. plantarum LR-14. In addition, whole genome sequencing analysis indicates that L. plantarum LR-14 contains various functional genes, including predicted extracellular polysaccharides (EPS) biosynthesis genes, and genes participating in the synthesis and metabolism of fatty acid, implying that L. plantarum LR-14 has the potential to be used as a probiotic with multiple functions.

Characterization of exopolysaccharide produced by probiotic Enterococcus durans DU1 and evaluation of its anti-biofilm activity

Exopolysaccharides (EPS) produced by lactic acid bacteria are complicated polymers with industrial applications. LAB were isolated, screened for EPS production, and their probiotic properties determined. The anti-biofilm activity of EPS was investigated. Safety of EPS-producing isolate was investigated and it was molecularly identified through 16S rRNA sequencing. Finally, anti-biofilm and emulsification activity of EPS was studied and it was characterized using FT-IR, TGA, ¹H-NMR, DLS and HPLC. Thirteen LAB were isolated from dairy products. They showed probiotic characteristics like acid resistance (0-6.51 CFU ml^-1) hydrophobicity (8-54.04%), autoaggregation (0% [t = 2 h]-99.8% [t = 24 h]) and coaggregation with food borne pathogens. Among them, Enterococcus durans DU1 had ability to produce EPS. EPS of Enterococcus durans DU1 showed antibiofilm activity against Y. enterocolitica (24.06-51.36%), S. aureus (12.33-49.6%), and B. cereus (11.66-27.16%). FT-IR showed this EPS had characteristic absorption peaks due to the presence of the pyran ring of sugars. ¹H NMR showed that EPS has N-acetyl, methyl, and alkyl groups in its structure. The HPLC analysis showed that EPS is a heteropolysaccharide and consists of sucrose, glucose, and fructose. EPS showed significant thermal stability (20% weight loss) under 300 °C and zeta potential of - 18.1 mV. This EPS can be used in the food industry with no adverse effect on consumers.

Optimization of cultural conditions for enhancement of anti-quorum sensing potential in the probiotic strain Lactobacillus rhamnosus GG against Pseudomonas aeruginosa

Disruption of quorum sensing (QS) system, which is a central regulator for pathogenesis of Pseudomonas aeruginosa, is referring to as quorum quenching (QQ). This study was undertaken to evaluate and enhance the anti-quorum sensing (AQS) potential of probiotic strain Lactobacillus rhamnosus GG. The cell-free supernatant (CFS) of this probiotic strain showed anti-quorum sensing activity against Pseudomonas aeruginosa, which was determined using well-diffusion agar-plate assay. Anti-quorum sensing potential of L. rhamnosus GG was enhanced by optimization of various cultural conditions using classical and statistical optimization approaches. Six variables were optimized using one-variable-at-a-time (OVAT) method. Four significant variables, viz., temperature, pH, incubation time, metal ion, and its concentration, were chosen for further optimization by response surface methodology (RSM) using central composite design (CCD). Analysis of variance (ANOVA) demonstrated that the regression model is highly significant, as indicated by F test with a low probability value (p  < 0.0002) and high value of coefficient of determination (0.8738) and also had significant influence on the generation of anti-quorum sensing effector molecules. Maximum production of anti-quorum sensing activity, in terms of zones of inhibition, was achieved under the following optimized conditions such as 37 °C temperature, pH 6.5, incubation time 24 h, and 2.5 mM concentration of zinc sulfate (ZnSO₄). The quadratic model predicted 1.3-fold increase anti-quorum sensing activity production over un-optimized cultural conditions. The present research is the first report representing the enhancement of anti-quorum sensing potential of L. rhamnosus GG.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03187-2.

Bacterial driver-passenger model in biofilms: a new mechanism in the development of colorectal cancer

Colorectal cancer (CRC) is a heterogeneous disease of the intestinal epithelium and ranks the third largest diagnosed malignancy in the world. Many studies have shown that the high risk of CRC is believed to be related to the formation of biofilms. To prove causation, it will be significant to decipher which specific bacteria in biofilms initiate and maintain CRC and fully describe their underlying mechanisms. Here we introduce a bacterial driver-passenger model. This model added a novel and compelling angle to the role of microorganisms, putting more emphasis on the transformation of bacterial composition in biofilms which play different roles in the development of CRC. In this model, bacterial drivers can initiate the formation of CRC through genotoxicity, while bacterial passengers maintain the CRC process through metabolites. On the basis of these pathogens, we further turned our attention to strategies that can inhibit and eradicate these pathogenic biofilms, with the aim of finding new ways to hinder colorectal carcinogenesis.

Combinatorial Therapeutic Strategy of Biogenics Derived from Lactobacillus fermentum PUM and Zingerone Against Pseudomonas aeruginosa PAO1-Induced Surgical Site Infection: an Experimental Study

Pseudomonas aeruginosa, a WHO-prioritized multidrug-resistant Gram-negative bacteria, is one of the frequently implicated pathogen in surgical site infection (SSI) due to its virulence phenotypes and biofilm-forming ability. In the present study, cell-free supernatant (CFS) and biogenics (organic acids and precipitated protein fraction) of indigenous potential probiotic, Lactobacillus fermentum PUM both alone and in combination with zingerone were found to inhibit pyocyanin, pyochelin, protease, elastase, the virulence factors, and motility of P. aeruginosa PAO1. Furthermore, scanning electron microscopy indicated that biofilm formation was attenuated maximally by CFS of L. fermentum combined with zingerone. In vivo study revealed reduced P. aeruginosa burden, suppuration at surgical site vis-a-vis reduced levels of oxidants, pro-inflammatory cytokines, ameliorated anti-oxidants, and healed infected surgical site compared with counter controls. In totality, combination of L. fermentum PUM-derived biogenics and zingerone could be employed to treat P. aeruginosa-induced SSI that needs to be correlated clinically.

Anti-biofilm potential of Lactobacillus plantarum Y3 culture and its cell-free supernatant against multidrug-resistant uropathogen Escherichia coli U12

Uropathogens develop biofilms on urinary catheters, resulting in persistent and chronic infections that are associated with resistance to antimicrobial therapy. Therefore, the current study was performed to control biofilm-associated urinary tract infections through assaying the anti-biofilm ability of lactic acid bacteria (LAB) against multidrug-resistant (MDR) uropathogens. Twenty LAB were obtained from pickles and fermented dairy products, and screened for their anti-biofilm and antimicrobial effects against MDR Escherichia coli U12 (ECU12). Lactobacillus plantarum Y3 (LPY3) (MT498405), showed the highest inhibitory effect and biofilm production. Pre-coating of a microtitre plate with LPY3 culture was more potent than co-incubation. Pre-coating with LPY3 culture generated a higher anti-biofilm effect with an adherence of 14.5% than cell free supernatant (CFS) (31.2%). Anti-biofilm effect of CFS was heat stable up to 100 °C with higher effect at pH 4-6. Pre-coating urinary catheter with LPY3 culture reduced the CFU/cm2 of ECU12 attached to the catheter for up to seven days. Meanwhile, CFS reduced the ECU12 CFU/cm2 for up to four days. Scanning electron microscope confirmed the reduction of ECU12 adherence to catheters after treatment with CFS. Therefore, Lactobacillus plantarum can be applied in medical devices as prophylactic agent and as a natural biointervention to treat urinary tract infections.

Probiotic characterization of Lactiplantibacillus plantarum HOM3204 and its restoration effect on antibiotic-induced dysbiosis in mice

The purpose of this study was to evaluate the probiotic characteristics of Lactiplantibacillus plantarum HOM3204 isolated from homemade pickled cabbage and to examine its restoration effect on antibiotic-induced dysbiosis in mice. Lact. plantarum HOM3204 tolerated simulated gastric and intestinal juices with a 99.38% survival rate. It also showed strong adhesion ability (3.45%) to Caco-2 cells and excellent antimicrobial activity against foodborne pathogens in vitro. For safety (antibiotic susceptibility) of this strain, it was susceptible to all the tested seven antibiotics. Lact. plantarum HOM3204 had good stability during storage, especially in cold and frozen conditions. Furthermore, Lact. plantarum HOM3204 significantly restored the gut microbiota composition by increasing the abundance of Lactobacilli and Bifidobacteria and decreasing Enterococci, and improved antioxidative function by raising the concentrations of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in serum of antibiotic-induced dysbiosis in mice. These results suggest that Lact. plantarum HOM3204 could be a potential probiotic as a functional food ingredient.

Probiotics as Therapeutic Tools against Pathogenic Biofilms: Have We Found the Perfect Weapon?

Bacterial populations inhabiting a variety of natural and human-associated niches have the ability to grow in the form of biofilms. A large part of pathological chronic conditions, and essentially all the bacterial infections associated with implanted medical devices or prosthetics, are caused by microorganisms embedded in a matrix made of polysaccharides, proteins, and nucleic acids. Biofilm infections are generally characterized by a slow onset, mild symptoms, tendency to chronicity, and refractory response to antibiotic therapy. Even though the molecular mechanisms responsible for resistance to antimicrobial agents and host defenses have been deeply clarified, effective means to fight biofilms are still required. Lactic acid bacteria (LAB), used as probiotics, are emerging as powerful weapons to prevent adhesion, biofilm formation, and control overgrowth of pathogens. Hence, using probiotics or their metabolites to quench and interrupt bacterial communication and aggregation, and to interfere with biofilm formation and stability, might represent a new frontier in clinical microbiology and a valid alternative to antibiotic therapies. This review summarizes the current knowledge on the experimental and therapeutic applications of LAB to interfere with biofilm formation or disrupt the stability of pathogenic biofilms.

Gibberellic acids promote growth and exopolysaccharide production in Tetraselmis suecica under reciprocal nitrogen concentration: an assessment on antioxidant properties and nutrient removal efficacy of immobilized iron-magnetic nanoparticles

The present study was aimed to assess the effect of gibberellic acids to enhance the growth, biomass, pigment, and exopolysaccharides production in Tetraselmis suecica under reciprocal nitrogen concentrations. For this study, the seven types of experimental media (N-P, NL-P/2GA3, N0-P/2GA3, NL-P/4GA3, N0-P/4GA3, NL-P/6GA3, and N0-P/6GA3) were prepared with the addition of gibberellic acids under various nitrogen concentrations. The experiment lasted for 15 days and the cell density, biomass, chlorophyll 'a', and exopolysaccharides (EPS) concentration of T. suecica were estimated for every 3 days. Then the EPS was subjected to the analyses of chemical (carbohydrate, protein, sulfate, and uronic acid), and antioxidant activity. In addition, nutrient removal efficiency was evaluated using different concentration of EPS. The highest DPPH (2,2-diphenyl-1-picrylhydrazyl) (86.7 ± 0.95%) and hydroxyl radical activity (85.7 ± 2.48%) were observed at the EPS concentrations 2.5 and 1.2 mg/mL, respectively. The immobilized magnetic Fe₃O₄-EPS (ferric oxide-exopolysaccharides) nanoparticles (5.0 and 10.0 g/L) have efficiently removed the excessive phosphate (89.5 ± 1.65%) and nitrate (73.5 ± 1.72%) from the Litopenaeus vannamei cultured wastewater. Thus, the application of gibberellic acids combined with limited nitrogen concentration could produce higher EPS that could exhibit excellent antioxidant activity, and nutrient removal efficacy in the form of Fe₃O₄-EPS magnetic nanoparticles.

Weissella confusa with thermostable β-hemolytic exopolysaccharide

Consuming cooked meat contaminated with bacteria that carry thermostable hemolytic exopolysaccharide (ESP), could lead to severe diseases. Culture of a 5- h boiled sample of meat goulash on blood agar showed growth of a gram positive rod-shaped, mucoid and hemolytic bacterium. Biochemical tests and amplification of 1500 bp product of 16S rDNA and sequencing revealed bacterial identity as Weissella confusa. After 1 h boiling of bacterial suspension, they were alive and hemolytic, increased in volume and aggregated. After 8 h boiling of bacterial suspension with coverslip, live bacteria showed hemolysis, clustered and adhered to coverslip. Bacterial bacteriocin and hemolytic activities remained unchanged upon autoclaving. Purified bacterial EPS retained hemolytic activity after autoclaving. Boiling contaminated meat had no negative impact on viability of heat-stable W. confusa and its hemolytic EPS. Thermostable hemolytic EPS protected W. confusa from excessive heat. Hygienic practice in butcheries and kitchens are necessary to eliminate bacterial contaminants.

Effect of Lactobacillus plantarum Biofilms on the Adhesion of Escherichia coli to Urinary Tract Devices

Novel technologies to prevent biofilm formation on urinary tract devices (UTDs) are continually being developed, with the ultimate purpose of reducing the incidence of urinary infections. Probiotics have been described as having the ability to displace adhering uropathogens and inhibit microbial adhesion to UTD materials. This work aimed to evaluate the effect of pre-established Lactobacillus plantarum biofilms on the adhesion of Escherichia coli to medical-grade silicone. The optimal growth conditions of lactobacilli biofilms on silicone were first assessed in 12-well plates. Then, biofilms of L. plantarum were placed in contact with E. coli suspensions for up to 24 h under quasi-static conditions. Biofilm monitoring was performed by determining the number of culturable cells and by confocal laser scanning microscopy (CLSM). Results showed significant reductions of 76%, 77% and 99% in E. coli culturability after exposure to L. plantarum biofilms for 3, 6 and 12 h, respectively, corroborating the CLSM analysis. The interactions between microbial cell surfaces and the silicone surface with and without L. plantarum biofilms were also characterized using contact angle measurements, where E. coli was shown to be thermodynamically less prone to adhere to L. plantarum biofilms than to silicone. Thus, this study suggests the use of probiotic cells as potential antibiofilm agents for urinary tract applications.

Bacteriocin of Pediococcus acidilactici HW01 Inhibits Biofilm Formation and Virulence Factor Production by Pseudomonas aeruginosa

Pseudomonas aeruginosa is a potential source of food contamination that leads to food spoilage and infections as a result of the generation of biofilm and virulence factors. In the present study, we demonstrate that bacteriocin produced by Pediococcus acidilactici HW01 (HW01 bacteriocin) effectively inhibited the biofilm formation of Ps. aeruginosa (66.41, 45.77, and 21.73% of biofilm formation at 0.5, 1, and 2 mg/mL of HW01 bacteriocin, respectively) as well as the production of virulence factors. By means of a microtiter plate method and scanning electron microscopy, HW01 bacteriocin inhibited biofilm formation by Ps. aeruginosa in a dose-dependent manner. Although the viability of biofilm cells of Ps. aeruginosa was reduced in the presence of HW01 bacteriocin, the viability of planktonic cells of Ps. aeruginosa was not affected by HW01 bacteriocin (2.0 × 10⁹ CFU/mL vs. 2.4 × 10⁹ CFU/mL in the absence and the presence of HW01 bacteriocin, respectively). Additionally, HW01 bacteriocin decreased the twitching motility of Ps. aeruginosa as well as the production of virulence factors, such as pyocyanin, protease, and rhamnolipid. Furthermore, HW01 bacteriocin significantly inhibited Ps. aeruginosa biofilm formation on the surface of stainless steel (57% reduction at 24 h and 83% reduction at 72 h). These results indicate that HW01 bacteriocin is an effective antagonist of Ps. aeruginosa as a result of its ability to inhibit biofilm formation and the production of virulence factors.

Impact of DMPEI on Biofilm Adhesion on Latex Urinary Catheter

BACKGROUND

Microorganisms can migrate from the external environment to the patient's organism through the insertion of catheters. Despite being indispensable medical device, the catheter surface can be colonized by microorganisms and become a starting point for biofilm formation. Therefore, new technologies are being developed in order to modify surfaces to prevent the adhesion and survival of microorganisms. Patents with the use of DMPEI have been filed.

OBJECTIVE

In the present work, we coated latex catheter surfaces with 2 mg mL-1 DMPEI in different solvents, evaluated the wettability of the surface and the anti- biofilm activity of the coated catheter against Escherichia coli, Staphylococcus aureus, and Candida albicans.

METHODS

We coated the inner and outer catheter surfaces with 2 mg mL-1 of DMPEI solubilized in butanol, dimethylformamide, and cyclohexanone and the surfaces were analyzed visually. Contact angle measurement allowed the analysis of the wettability of the surfaces. The CFU mL-1 count evaluated E. coli, S. aureus, and C. albicans adhesion onto the control and treated surfaces.

RESULTS

The contact angle decreased from 50.48º to 46.93º on the inner surface and from 55.83º to 50.91º on the outer surface of latex catheters coated with DMPEI. The catheter coated with DMPEI showed anti-biofilm activity of 83%, 88%, and 93% on the inner surface and 100%, 92%, and 86% on the outer surface for E. coli, S. aureus, and C. albicans, respectively.

CONCLUSION

Latex catheter coated with DMPEI efficiently impaired the biofilm formation both on the outer and inner surfaces, showing a potential antimicrobial activity along with a high anti-biofilm activity for medical devices.

Synergistic Effect of Biogenics Derived from Potential Probiotics Together with Zingerone Against Biofilm Formation by Pseudomonas aeruginosa PAO1

Biogenics are compounds produced by living organisms such as animals, plants, bacteria, etc. Probiotics and their biogenics are known for their antimicrobial potential. Therefore, the present study was designed to evaluate the antibiofilm potential of probiotic-derived biogenics in conjunction with zingerone against the Pseudomonas aeruginosa PAO1 biofilm. Cell-free supernatant (CFS) of potential probiotics Pediococcus acidilactici BNS5B and Lactobacillus fermentum PUM was found to inhibit the growth of Ps. aeruginosa PAO1 maximally among the nineteen isolated lactic acid bacteria. L. fermentum PUM produced precipitated protein fraction (PP), organic acids (OAs), exopolysaccharides (EPSs), biosurfactants (BSs) and various volatile antimicrobial compounds, while Ped. acidilactici BNS5B was found to produce PP, OA, EPS, BS and fewer volatile antimicrobial compounds only. More specifically, CFS and selected biogenics (OA and PP from L. fermentum PUM; OA from Ped. acidilactici BNS5B) of both potential probiotics showed synergy with zingerone against Ps. aeruginosa growth as observed by FIC index (< 0.5). Interestingly, CFS of both potential probiotics in combination with zingerone led to the formation of a more distorted biofilm compared with OA of L. fermentum PUM and zingerone, OA of Ped. acidilactici BNS5B and zingerone, PP of L. fermentum PUM and zingerone as well as their individual counterparts. Similarly, both confocal laser scanning microscopy and XTT assay showed an increased number of dead and impaired cells along with the decreased viability of biofilm cells. Thus, it can be reckoned that a combination of probiotic-derived biogenics and zingerone can have therapeutic application against Ps. aeruginosa infections which needs to be validated clinically.

The Use of Probiotics to Fight Biofilms in Medical Devices: A Systematic Review and Meta-Analysis

Medical device-associated infections (MDAI) are a critical problem due to the increasing usage of medical devices in the aging population. The inhibition of biofilm formation through the use of probiotics has received attention from the medical field in the last years. However, this sparse knowledge has not been properly reviewed, so that successful strategies for biofilm management can be developed. This study aims to summarize the relevant literature about the effect of probiotics and their metabolites on biofilm formation in medical devices using a PRISMA-oriented (Preferred Reporting Items for Systematic reviews and Meta-Analyses) systematic search and meta-analysis. This approach revealed that the use of probiotics and their products is a promising strategy to hinder biofilm growth by a broad spectrum of pathogenic microorganisms. The meta-analysis showed a pooled effect estimate for the proportion of biofilm reduction of 70% for biosurfactants, 76% for cell-free supernatants (CFS), 77% for probiotic cells and 88% for exopolysaccharides (EPS). This review also highlights the need to properly analyze and report data, as well as the importance of standardizing the in vitro culture conditions to facilitate the comparison between studies. This is essential to increase the predictive value of the studies and translate their findings into clinical applications.

The potential of Streptococcus salivarius oral films in the management of dental caries: An inkjet printing approach

The use of probiotics, which can be administered in oro-dispersible films (ODFs) and have prolonged activity in the mouth, was explored. ODFs made of xylitol and containing Streptococcus salivarius were formulated using inkjet printing and tested against Streptococcus mutans - a causative organism of dental caries. The testing of the prepared ODFs involved co-incubating an ink-jetted formulation of S. salivarius and xylitol with S. mutans and monitoring the microbial growth kinetics in real-time using isothermal microcalorimetry and colony plate counts. Cell-free supernatants (CFS) of S. salivarius were also tested against S. mutans. The phosphate solubilisation potential of S. salivarius was also determined and found to be negative, an indication that the species will not deplete phosphate from teeth. From the tests, it was observed that the formulation reduced the S. mutans population from 7.9 to 5.04 Log CFU/mL post-calorimetry (approximately 3 Log reduction) which was comparable to the 99.9% reduction expected during antimicrobial activity testing. A gradual decrease in S. mutans population was also observed with increasing of CFS of S. salivarius volumes indicative of pathogen suppression. This study demonstrates that S. salivarius can be useful in managing dental caries and ODFs of S. salivarius can be formulated easily using ink-jetting for such management.

Postbiotics against Pathogens Commonly Involved in Pediatric Infectious Diseases

The Sustainable Development goals for 2020 included reducing all causes associated with infant and perinatal mortality in their priorities. The use of compounds with bioactive properties has been proposed as a therapeutic strategy due to their stimulating effect on the host's immune system. Additionally, biotherapeutic products such as postbiotics, tentatively defined as compounds produced during a fermentation process that support health and well-being, promote intestinal barrier integrity without posing considerable risks to children's health. Although this is a concept in development, there are increasing studies in the field of nutrition, chemistry, and health that aim to understand how postbiotics can help prevent different types of infections in priority populations such as minors under the age of five. The present review aims to describe the main mechanisms of action of postbiotics. In addition, it presents the available current evidence regarding the effects of postbiotics against pathogens commonly involved in pediatric infections. Postbiotics may constitute a safe alternative capable of modulating the cellular response and stimulating the host's humoral response.

A strategy to control colonization of pathogens: embedding of lactic acid bacteria on the surface of urinary catheter

Indwelling urinary catheterization is one of the major causes of urinary tract infection (UTI) in hospitalized patients worldwide. A catheter serves as a surface for the colonization and formation of biofilm by UTI-related pathogenic bacteria. To combat the biofilm formation on its surface, several strategies have already been employed such as coating it with antibiofilm and antimicrobial compounds. For instance, the application of lactic acid bacteria (LAB) offers a potential strategy for the treatment of biofilm formation on the surface of the urinary catheter due to its ability to kill the pathogenic bacteria. The killing of pathogenic bacteria by LAB occurs via the production of antimicrobial compounds such as lactic acid, bacteriocin, and hydrogen peroxide. LAB also displays a competitive exclusion mechanism to prevent the adhesion of pathogens on the surfaces. Hence, LAB has been extensively applied as a bacteriotherapy to combat infectious diseases. Several strategies have been employed to attach LAB to a surface, but its easy detachment during long time exposure becomes one of the drawbacks in its application. Here, we have proposed a novel strategy for its adhesion on the surface of the urinary catheter with the utilization of mannose-specific adhesin (Msa) protein in a way similar as uropathogenic bacteria interacts between Msa present on the tip of the type I fimbriae/pilus and the mannose moieties on the host epithelial cell surfaces. KEY POINTS: • Urinary tract infection (UTI) is one of the common hospital-acquired infections, which is associated with the application of an indwelling urinary catheter. • Based on the competitive exclusions properties of LAB, attachment of the LAB on the catheter surface would be a promising approach to control the formation of pathogenic biofilm. • The strategy employed for the adhesion of LAB is via a covalent interaction of its mannose-specific adhesin (Msa) protein to the mannose residues grafted on the catheter surface.

Postbiotics produced by lactic acid bacteria: The next frontier in food safety

There are many critical challenges in the use of primary and secondary cultures and their biological compounds in food commodities. An alternative is the application of postbiotics from the starter and protective lactic acid bacteria (LAB). The concept of postbiotics is relatively new and there is still not a recognized definition for this term. The word "postbiotics" is currently used to refer to bioactive compounds, which did not fit to the traditional definitions of probiotics, prebiotics, and paraprobiotics. Therefore, the postbiotics may be presently defined as bioactive soluble factors (products or metabolic byproducts), produced by some food-grade microorganisms during the growth and fermentation in complex microbiological culture (in this case named cell-free supernatant), food, or gut, which exert some benefits to the food or the consumer. Many LAB are considered probiotic and their postbiotic compounds present similar or additional health benefits to the consumer; however, this review aimed to address the most recent applications of the postbiotics with food safety purposes. The potential applications of postbiotics in food biopreservation, food packaging, and biofilm control were reviewed. The current uses of postbiotics in the reduction and biodegradation of some food safety-related chemical contaminants (e.g., biogenic amines) were considered. We also discussed the safety aspects, the obstacles, and future perspectives of using postbiotics in the food industry. This work will open up new insights for food applications of postbiotics prepared from LAB.

Targeting Gut Microbial Biofilms-A Key to Hinder Colon Carcinogenesis?

Colorectal cancer (CRC) is a global public health issue which poses a substantial humanistic and economic burden on patients, healthcare systems and society. In recent years, intestinal dysbiosis has been suggested to be involved in the pathogenesis of CRC, with specific pathogens exhibiting oncogenic potentials such as Fusobacterium nucleatum, Escherichia coli and enterotoxigenic Bacteroides fragilis having been found to contribute to CRC development. More recently, it has been shown that initiation of CRC development by these microorganisms requires the formation of biofilms. Gut microbial biofilm forms in the inner colonic mucus layer and is composed of polymicrobial communities. Biofilm results in the redistribution of colonic epithelial cell E-cadherin, increases permeability of the gut and causes a loss of function of the intestinal barrier, all of which enhance intestinal dysbiosis. This literature review aims to compile the various strategies that target these pathogenic biofilms and could potentially play a role in the prevention of CRC. We explore the potential use of natural products, silver nanoparticles, upconverting nanoparticles, thiosalicylate complexes, anti-rheumatic agent (Auranofin), probiotics and quorum-sensing inhibitors as strategies to hinder colon carcinogenesis via targeting colon-associated biofilms.

The Battle of Probiotics and Their Derivatives Against Biofilms

Biofilm-related infections have been a major clinical problem and include chronic infections, device-related infections and malfunction of medical devices. Since biofilms are not fully available for the human immune system and antibiotics, they are difficult to eradicate and control; therefore, imposing a global threat to human health. There have been avenues to tackle biofilms largely based on the disruption of their adhesion and maturation. Nowadays, the use of probiotics and their derivatives has gained a growing interest in battling against pathogenic biofilms. In the present review, we have a close look at probiotics with the ultimate objective of inhibiting biofilm formation and maturation. Overall, insights into the mechanisms by which probiotics and their derivatives can be used in the management of biofilm infections would be warranted.

Influence of cell-free extracts of Bifidobacterium bifidum and Lactobacillus reuteri on proliferation and biofilm formation by Escherichia coli and Pseudomonas aeruginosa

The development of new effective preparations for the correction of microecological disorders based on probiotic derivatives requires a comprehensive study of the biological activity of the latter. We studied the proliferative activity and biofilm formation by clinical isolates: Escherichia coli and Pseudomonas aeruginosa under the influence of cell-free extracts containing structural components and metabolites of the Bifidobacterium bifidum and Lactobacillus reuteri probiotic strains. Cell-free extracts were obtained from disintegrates and cultures of probiotics. Disintegrates were prepared by cyclic freezing-thawing of probiotic cell suspensions. The cultures were obtained by cultivating probiotic microorganisms in their own disintegrates. The obtained disintegrates and cultures were filtered. The proliferative activity of the test cultures was studied using the spectrophotometric microtiter plate method after an hour-long exposure in undiluted cell-free extracts and subsequent cultivation in a nutrient medium containing 30%vol of the studied extracts at 37 °C for 24 hours. The biofilm formation of the test cultures was studied with 30% vol content of cell-free extracts in the cultivation medium using the spectrophotometric microtiter plate method. All the studied extracts exerted a similar effect on the proliferative activity and biofilm formation by E. coli and P. aeruginosa. Exposure of the test cultures in all undiluted extracts during an hour led to a significant decrease in the optical density of the test samples: optical density of the test wells ranged from 36.5% to 49.8% of the control wells. The test cultures that were exposed to the extracts: filtrate of L. reuteri disintegrate (L), filtrate of В. bifidum disintegrate (B) and filtrate of В. bifidum culture, grown in В. bifidum disintegrate (MB) after dilution and subsequent cultivation over the next 24 hours completely restored the ability to proliferate. The proliferative activity of the test cultures that were exposed to the extracts: filtrate of L. reuteri culture, grown in L. reuteri disintegrate (ML) and filtrate of L. reuteri culture, grown in L. reuteri disintegrate supplemented with 0.8 M glycerol and 0.4 M glucose (MLG), was significantly inhibited after dilution and subsequent cultivation. The inhibition indices calculated for the ML extract were: 25.9% (E. coli) and 53.0% (P. aeruginosa). Inhibition indices calculated for the MLG extract were: 62.0% (E. coli) and 96.9% (P. aeruginosa). MLG extract had more pronounced inhibitory effect on the proliferation of the test cultures than ML extract. All the studied extracts exerted significant inhibitory effect on the biofilm formation of the test cultures. Analysis of the results of the study shows that cell-free extracts of L. reuteri culture grown in its disintegrate without supplementation or supplemented with glycerol and glucose have the highest antimicrobial activity and can be used as metabiotics to prevent overgrowth of potentially pathogenic bacteria, as well as inoculation and proliferation of pathogenic gram-negative bacteria in the gastrointestinal tract. They can be used alone or in combination with cellular probiotics to enhance their probiotic action. This study encourages further careful investigation of the biochemical composition of cell-free extracts and clarifying the mechanism of their action.

Antibacterial and anti-adhesive efficiency of Pediococcus acidilactici against foodborne biofilm producer Bacillus cereus attached on different food processing surfaces

This study aimed to assess the biofilm formation by Bacillus cereus on two novel surfaces namely: aluminum and cold steel in comparison study with stainless steel and polystyrene. Also, it aimed to study the inhibitory effect of a new strain Pediococcus acidilactici against biofilm formation by B. cereus grown on these surfaces. In this study, B. cereus M50 isolated from milky machine surface was selected as the highest biofilm producer. The number of M50 cells adhered to aluminum and stainless steel surfaces were more than that adhered to polystyrene and cold steel, respectively. The antimicrobial, anti-adhesive and SEM studies revealed that the P. acidilactici P12 culture and its cell free filtrate showed a significant potential inhibition of biofilm formation of M50 on all tested surfaces under different conditions. These results demonstrated that P. acidilactici strain are considered a new biotreatment for biofilm destruction of food borne pathogens, food biopreservation and food safety.