Potential Properties of Lactobacillus plantarum F-10 as a Bio-control Strategy for Wound Infections

Probiotics in Wound Healing

Wound infections caused by opportunistic bacteria promote persistent infection and represent the main cause of delayed healing. Probiotics are acknowledged for their beneficial effects on the human body and could be utilized in the management of various diseases. They also possess the capacity to accelerate wound healing, due to their remarkable anti-pathogenic, antibiofilm, and immunomodulatory effects. Oral and topical probiotic formulations have shown promising openings in the field of dermatology, and there are various in vitro and in vivo models focusing on their healing mechanisms. Wound dressings embedded with prebiotics and probiotics are now prime candidates for designing wound healing therapeutic approaches to combat infections and to promote the healing process. The aim of this review is to conduct an extensive scientific literature review regarding the efficacy of oral and topical probiotics in wound management, as well as the potential of wound dressing embedding pre- and probiotics in stimulating the wound healing process.

The role of the skin microbiome in wound healing

The efficient management of skin wounds for rapid and scarless healing represents a major clinical unmet need. Nonhealing skin wounds and undesired scar formation impair quality of life and result in high healthcare expenditure worldwide. The skin-colonizing microbiota contributes to maintaining an intact skin barrier in homeostasis, but it also participates in the pathogenesis of many skin disorders, including aberrant wound healing, in many respects. This review focuses on the composition of the skin microbiome in cutaneous wounds of different types (i.e. acute and chronic) and with different outcomes (i.e. nonhealing and hypertrophic scarring), mainly based on next-generation sequencing analyses; furthermore, we discuss the mechanistic insights into host-microbe and microbe-microbe interactions during wound healing. Finally, we highlight potential therapeutic strategies that target the skin microbiome to improve healing outcomes.

Strong Activity and No Resistance Induction Exerted by Cell-Free Supernatants from Lacticaseibacillus rhamnosus against Mono-Species and Dual-Species Biofilms of Wound Pathogens in In Vivo-like Conditions

It is widely agreed that microbial biofilms play a major role in promoting infection and delaying healing of chronic wounds. In the era of microbial resistance, probiotic strains or their metabolic products are emerging as an innovative approach for the treatment of hard-to-heal (chronic) wounds due to their antimicrobial, healing, and host immune-modulatory effects. In this study, we aimed to investigate the potential of cell-free supernatants (CFS) from Lacticaseibacillus rhamnosus GG against mono- and dual-species biofilms of wound pathogens in a 3D in vitro infection model. Mature biofilms of Pseudomonas aeruginosa and Staphylococcus aureus were obtained on collagen scaffolds in the presence of a simulant wound fluid (SWF) and treated with CFS at different doses and time intervals. At 1:4 dilution in SWF, CFS caused a marked reduction in the colony forming-unit (CFU) numbers of bacteria embedded in mono-species biofilms as well as bacteria released by the biofilms in the supernatant. CFU count and electron microscopy imaging also demonstrated a marked antibiofilm effect against dual-species biofilms starting from 8 h of incubation. Furthermore, CFS exhibited acceptable levels of cytotoxicity at 24 h of incubation against HaCaT cells and, differently from ciprofloxacin, failed to induce resistance after 15 passages at sub-inhibitory concentrations. Overall, the results obtained point to L. rhamnosus GG postbiotics as a promising strategy for the treatment of wound biofilms.

Biofilm therapy for chronic wounds

Chronic wounds have been a major factor of serious harm to global public health. At present, it is known that almost all chronic wounds contain biofilms, which seriously hinder the healing process. Removal of biofilms can effectively promote the healing of chronic wounds. As the study of wound biofilms deepens, many new treatment methods have emerged, thus bringing revolutionary means for the treatment of chronic wound biofilm. This review summarizes various methods for the treatment of chronic wound biofilm worldwide to provide a theoretical summary and practical basis for the selection of suitable wound biofilm treatment methods in clinical practice.

Healing wounds, defeating biofilms: Lactiplantibacillus plantarum in tackling MRSA infections

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) infections are well-known hospital-borne infections and are a major contributing factor to global health concerns of antimicrobial resistance due to the formation of biofilms. Probiotics are known to assist in the healing of wounds through immunomodulation and also possess anti-pathogen properties via competitive inhibition. The probiotic bacterium, Lactiplantibacillus plantarum MTCC 2621 and its cell-free supernatant (Lp2621) have previously been reported to have antibacterial, excellent antioxidant, and wound healing activity in in vitro conditions and wounds contaminated with S. aureus in mice.

Methods

In the current study, we evaluated its anti-MRSA, biofilm inhibition and eradication efficacy, immunomodulatory activity in THP-1 cells, and wound healing potential in wounds contaminated with MRSA infection in mice.

Results

In agar well diffusion assay, Lp2621 showed anti-MRSA activity and revealed dose-dependent inhibition and eradication of biofilm by crystal violet assay as well as by Confocal Scanning Laser Microscopy (CLSM) analysis. Further, Lp2621 showed immunomodulatory activity at varied concentrations as measured by IL-6 and IL-10 gene expression in THP-1 cells. Similar findings were observed in serum samples of mice after treatment of excision wound contaminated with MRSA infection by Lp2621 gel, as evident by expression of IL-6 (pro-inflammatory) and IL-10 (anti-inflammatory) cytokines.

Conclusions

Overall, our results show that Lp2621 has potent anti-MRSA and antioxidant properties and can prevent and eliminate biofilm formation. It also showed promise when applied to mice with MRSA-infected wounds.

Nanocurcumin and viable Lactobacillus plantarum based sponge dressing for skin wound healing

Curcumin loaded solid lipid nanoparticles (CSLNs) and probiotic (Lactobacillus plantarum UBLP-40; L. plantarum) were currently co-incorporated into a wound dressing. The combination with manifold anti-inflammatory, anti-infective, analgesic, and antioxidant properties of both curcumin and L. plantarum will better manage complex healing process. Recent reports indicate that polyphenolics like curcumin improve probiotic effects. Curcumin was nanoencapsulated (CSLNs) to improve its bioprofile and achieve controlled release on the wound bed. Bacteriotherapy (probiotic) is established to promote wound healing via antimicrobial activity, inhibition of pathogenic toxins, immunomodulation, and anti-inflammatory actions. Combination of CSLNs with probiotic enhanced (560%) its antimicrobial effects against planktonic cells and biofilms of skin pathogen, Staphylococcus aureus 9144. The sterile dressing was devised with selected polymers, and optimized for polymer concentration, and dressing characteristics using a central composite design. It exhibited a swelling ratio of 412 ± 36%, in vitro degradation time of 3 h, optimal water vapor transmission rate of 1516.81 ± 155.25 g/m2/day, high tensile strength, low-blood clotting index, case II transport, and controlled release of curcumin. XRD indicated strong interaction between employed polymers. FESEM revealed a porous sponge like meshwork embedded with L. plantarum and CSLNs. It degraded and released L. plantarum, which germinated in the wound bed. The sponge was stable under refrigerated conditions for up to six months. No translocation of probiotic from wound to the internal organs confirmed safety. The dressing exhibited faster wound closure and lowered bioburden in the wound area in mice. This was coupled with a decrease in TNF-α, MMP-9, and LPO levels; and an increase in VEGF, TGF-β, and antioxidant enzymes such as catalase and GSH, establishing multiple healing pathways. Results were compared with CSLNs and probiotic-alone dressings. The dressing was as effective as the silver nanoparticle-based marketed hydrogel dressing; however, the cost and risk of developing resistance would be much lower currently.

The Potential of Lactiplantibacillus plantarum ATCC 14917 in the Development of Alginate-Based Gel Formulations with Anti-Staphylococcus aureus Properties

This study aimed to evaluate the potential of lactic acid bacteria (LAB) in developing alginate-based gel formulations to inhibit Staphylococcus aureus. Initially, the antagonistic actions of three lactic acid bacteria (LAB) (Lacticaseibacillus rhamnosus ATCC 10863, Lactiplantibacillus plantarum ATCC 14917, Limosilactobacillus fermentum ATCC 23271) were evaluated against S. aureus ATCC 25923. All tested LAB inhibited S. aureus, but the highest activity was observed for L. plantarum ATCC 14917 (p < 0.05). The antimicrobial effects of L. plantarum ATCC 14917 cell suspensions, sonicate cells extract, and cell-free supernatants (pH 5 or 7) were analyzed using a broth-based assay. The cell suspensions inhibited S. aureus at concentrations ≥ 10%, and these effects were confirmed by a time-kill assay. Alginate-based gels were formulated with cell suspensions, sonicate cells extract, and cell-free supernatant (pH 5). These formulations inhibited S. aureus growth. Based on the results, the alginate gel with cell suspensions at 10% was selected for further characterization. L. plantarum ATCC 14917 survived in the alginate-based gel, especially when stored at 5 °C. At this temperature, the L. plantarum-containing alginate gel was stable, and it was in compliance with microbiological standards. These findings suggest it can be a promising agent for the topical treatment of infections induced by S. aureus.

ESKAPEE Pathogen Biofilm Control on Surfaces with Probiotic Lactobacillaceae and Bacillus species

Combatting the rapidly growing threat of antimicrobial resistance and reducing prevalence and transmission of ESKAPEE pathogens in healthcare settings requires innovative strategies, one of which is displacing these pathogens using beneficial microorganisms. Our review comprehensively examines the evidence of probiotic bacteria displacing ESKAPEE pathogens, with a focus on inanimate surfaces. A systematic search was conducted using the PubMed and Web of Science databases on 21 December 2021, and 143 studies were identified examining the effects of Lactobacillaceae and Bacillus spp. cells and products on the growth, colonization, and survival of ESKAPEE pathogens. While the diversity of study methods limits evidence analysis, results presented by narrative synthesis demonstrate that several species have the potential as cells or their products or supernatants to displace nosocomial infection-causing organisms in a variety of in vitro and in vivo settings. Our review aims to aid the development of new promising approaches to control pathogen biofilms in medical settings by informing researchers and policymakers about the potential of probiotics to combat nosocomial infections. More targeted studies are needed to assess safety and efficacy of different probiotic formulations, followed by large-scale studies to assess utility in infection control and medical practice.

Isolation of lectin from Musa acuminata for its antibiofilm potential against Methicillin-resistant Staphylococcus aureus and its synergistic effect with Enterococcus species

Methicillin resistant Staphylococcus aureus (MRSA) is an emerging pathogen posing a considerable burden on the healthcare system due to its involvement in skin and soft tissue infections (SSTIs). Lectins are carbohydrate binding proteins found ubiquitously in animals, plants and microorganisms. Extraction and isolation of proteins from Musa acuminata were performed by using Affinity chromatography with Sephadex G 75 to determine antibiofilm activity against MRSA. Enterococcus strains obtained from dairy products, beans and vegetables were also screened for its potential to inhibit growth and biofilm formation of MRSA by using 96 well microtiter plates. Synergistic effect of cell free supernatant of Enterococcus with proteins from ripe banana were also tested. BanLec was successfully isolated and appeared as 15 KDa band after SDS-PAGE (15%) while multiple bands of unbound protein fractions were observed. The unbound fractions showed inhibition of planktonic cells and biofilm but BanLec exhibited no significant effect. The CFS of Enterococcus faecium (LCM002), Enterococcus lactis (LCM003) and Enterococcus durans (LCM004 and LCM005) displayed antagonistic effects against pathogen. The synergistic effect of CFS from E. lactis (LCM003) and unbound proteins showed inhibition of biofilm and pathogenic growth. This study demonstrates the use of Enterococcus species and plant proteins against pathogens and results suggested that it can inhibit the growth of resistant strains of Staphylococcus aureus and their synergistic effect has opened new ways to tackle emerging resistance. Furthermore, after assessment of Enterococcus as probiotics, this could be used in food industries as well as in treatment of severe skin infections.

Development and Characterization of Hydroxyethyl Cellulose-Based Gels Containing Lactobacilli Strains: Evaluation of Antimicrobial Effects in In Vitro and Ex Vivo Models

This study aimed to develop a hydroxyethyl cellulose-based topical formulation containing probiotics and to evaluate its antimicrobial action using in vivo and ex vivo models. Initially, the antagonistic effects of Lacticaseibacillus rhamnosus ATCC 10863, Limosilactobacillus fermentum ATCC 23271, Lactiplantibacillus plantarum ATCC 8014 and Lactiplantibacillus plantarum LP-G18-A11 were analyzed against Enterococcus faecalis ATCC 29212, Klebsiella pneumoniae ATCC 700603, Staphylococcus aureus ATCC 27853 and Pseudomonas aeruginosa ATCC 2785. The best action was seen for L. plantarum LP-G18-A11, which presented high inhibition against S. aureus and P. aeruginosa. Then, lactobacilli strains were incorporated into hydroxyethyl cellulose-based gels (natrosol); however, only the LP-G18-A11-incorporated gels (5% and 3%) showed antimicrobial effects. The LP-G18-A11 gel (5%) maintained its antimicrobial effects and viability up to 14 and 90 days at 25 °C and 4 °C, respectively. In the ex vivo assay using porcine skin, the LP-G18-A11 gel (5%) significantly reduced the skin loads of S. aureus and P. aeruginosa after 24 h, while only P. aeruginosa was reduced after 72 h. Moreover, the LP-G18-A11 gel (5%) showed stability in the preliminary and accelerated assays. Taken together, the results show the antimicrobial potential of L. plantarum LP-G18-A11, which may be applied in the development of new dressings for the treatment of infected wounds.

The Emerging Role of Probiotics and their Derivatives against Biofilm-Producing MRSA: A Scoping Review

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the main bacterial pathogens causing chronic infections, mainly because of its capacity to produce biofilm. Biofilm production is one of the underlying strategies for antibacterial drug resistance. Accordingly, preventing and attenuating biofilm production has become an emerging approach to controlling persistent infections. Therefore, this scoping review is aimed at surveying the published literature describing the usage of probiotics and their derivatives against biofilm-producing MRSA.

Methods

Updated literature searches were conducted across seven electronic databases including Web of Science, PubMed, Scopus, Cochrane Library, ProQuest, Embase, and Google Scholar to identify all original published articles about probiotics against MRSA. In this regard, studies were summarized and analyzed in the present review.

Results

In the reviewed studies, various microorganisms and compounds were used as probiotics as follows: Lactobacillus species (8 studies), Enterococcus species (4 studies), Bacillus species (2 studies), Streptomyces species (2 studies), Saccharomyces cerevisiae (1 study), Corynebacterium accolens (1 study), and Lactococcus lactis derived Nisin (3 studies). Based on our comprehensive search, 21 studies with eligibility criteria were included in the present review including 12 studies on clinical strains, 6 studies on ATCC, 2 studies simultaneously on clinical and standard strains, and finally 1 study on food sample.

Conclusions

Our study showed that there was an increasing trend in the number of publications reporting probiotics against biofilm-producing MRSA. The results of this scoping review could use to guide the undertaking of the subsequent systematic reviews. In summary, probiotics with antimicrobial and antibiofilm properties can use as an embedded agent in food products or as a biopharmaceutical in the prevention and treatment of MRSA infections.

Lactic acid bacteria: prominent player in the fight against human pathogens

INTRODUCTION

The human microbiome is a unique repository of diverse bacteria. Over 1000 microbial species reside in the human gut, which predominantly influences the host's internal environment and plays a significant role in host health. Lactic acid bacteria have long been employed for multiple purposes, ranging from food to medicines. Lactobacilli, which are often used in commercial food fermentation, have improved to the point that they might be helpful in medical applications.

AREAS COVERED

This review summarises various clinical and experimental evidence on efficacy of lactobacilli in treating a wide range of infections. Both laboratory based and clinical studies have been discussed.

EXPERT OPINION

Lactobacilli are widely accepted as safe biological treatments and host immune modulators (GRAS- Generally regarded as safe) by the US Food and Drug Administration and Qualified Presumption of Safety. Understanding the molecular mechanisms of lactobacilli in the treatment and pathogenicity of bacterial infections can help with the prediction and development of innovative therapeutics aimed at pathogens which have gained resistance to antimicrobials. To formulate effective lactobacilli based therapy significant research on the effectiveness of different lactobacilli strains and its association with demographic distribution is required. Also, the side effects of such therapy needs to be evaluated.

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.

Development of guar gum-based dual-layer wound dressing containing Lactobacillus plantarum: Rapid recovery and mechanically flexibility

This study aimed to develop a Lactobacillus plantarum (L. plantarum)-loaded dual-layer wound dressing (DLD) with excellent wound recovery and mechanical properties. L. plantarum-loaded DLD was fabricated by covering the hydrogel (inner layer) with a hydrocolloid (external layer). The hydrocolloid was manufactured by the hot-melt method, consisting of liquid paraffin, polyisobutylene, styrene-isoprene-styrene, and sodium carboxymethylcellulose (12:20:25:43, w/w/w/w). In contrast, the hydrogel was fabricated by the freeze-and-thaw method to load heat-labile L. plantarum. Various non-ionic materials have been investigated to select appropriate hydrogel components. The hydrogel composed of L. plantarum stock solution, guar gum, and polyvinyl alcohol (10:2:10, w/w/w) was chosen for its excellent swelling capacity and mechanical properties. As a result, heat-labile L. plantarum was successfully loaded into the guar-gum-based DLD. Moreover, guar gum-based DLD containing L. plantarum exhibited significantly enhanced swelling capacity and elasticity compared to single hydrogel layer (swelling capacity: DLD, 920.7 ± 32.4 % vs. hydrogel, 282.2 ± 6.5 %; elastic modulus: DLD, 2.9 ± 0.3 × 10^-3 N/mm² vs. hydrogel, 4.2. ± 0.7 × 10^-3 N/mm²). The wound recovery test using Pseudomonas aeruginosa-infected animal model and histological profiles confirmed guar gum-based DLD containing L. plantarum to elicit accelerated wound recovery with complete re-epithelialization compared to commercial product and non-treated (recovery rate at Day 3: DLD, 67.8 ± 6.2 % vs. commercial product, 30.4 ± 11.7 % vs. non-treated, 14.2 ± 7.5 %). Therefore, L. plantarum-loaded DLD is an effective system for wound treatment.

Antibiofilm and Antiquorum Sensing Potential of Lactiplantibacillus plantarum Z057 against Vibrio parahaemolyticus

Vibrio parahaemolyticus is a widespread foodborne pathogen that causes serious seafood-borne gastrointestinal infections. Biofilm and quorum sensing (QS) are critical in regulating these infections. In this study, first, the ability of Lactiplantibacillus plantarum Z057 to compete, exclude, and displace V. parahaemolyticus biofilm was evaluated. Then, the inhibitory effects of L. plantarum Z057 extract (Z057-E) on V. parahaemolyticus biofilm and QS were explored from the aspects of biofilm biomass, metabolic activity, physicochemical properties, extracellular polymer matrix content, QS signal AI-2 activity, biofilm microstructure, and the expression levels of biofilm and QS-related genes. Results showed that L. plantarum Z057 effectively inhibited biofilm formation of V. parahaemolyticus and interfered with the adhesion of V. parahaemolyticus on the carrier surface. In addition, the Z057-E could significantly reduce the biofilm biomass, metabolic activity, hydrophobicity, auto-aggregation ability, swimming and swarming migration diameter, AI-2 activity, extracellular polysaccharide (EPS), and extracellular protein content of V. parahaemolyticus. Fluorescence microscope and scanning electron microscope (SEM) images demonstrated that the Z057-E could efficiently inactivate the living cells, destroy the dense and complete biofilm architectures, and reduce the essential component of the extracellular polymer matrix. Real-time fluorescence quantitative PCR revealed that the Z057-E treatment down-regulated the expression of flagellum synthesis-related genes (flaA, flgM), EPS, and extracellular protein synthesis-related genes (cpsA, cpsQ, cpsR, ompW), QS-related genes (luxS, aphA, opaR), and hemolysin secretion-related genes (toxS, toxR) of V. parahaemolyticus. Thus, our results suggested that L. plantarum Z057 could represent an alternative biocontrol strategy against foodborne pathogens with anti-adhesive, antibiofilm, and antiquorum sensing activities.

Biosynthesized Silver Nanoparticles from Eruca sativa Miller Leaf Extract Exhibits Antibacterial, Antioxidant, Anti-Quorum-Sensing, Antibiofilm, and Anti-Metastatic Activities

Worldwide, the primary problem today is the proliferation of cancer and secondary bacterial infections caused by biofilms, as they are the principal causes of death due to the lack of effective drugs. A great deal of biological activities of silver nanoparticles (AgNPs) have made them a brilliant choice for the development of new drugs in recent years. The present study was conducted to evaluate the anticancer, antibacterial, anti-QS, and antibiofilm effects of AgNPs synthesized from Eruca sativa (E. sativa) leaf extract. The ultraviolet–visible (UV–Vis) spectra showed a peak of surface plasmon resonance at 424 nm λmax, which corresponded to AgNP formation. The Fourier transform infrared spectroscopy (FT-IR) confirmed that biological moieties are involved for the development of AgNPs. Moreover, transmission electron microscopy (TEM) analyses confirmed the spherical shape and uniform size (8.11 to 15 nm) of the AgNPs. In human lung cancer cells (A549), the anticancer potential of AgNPs was examined by the MTT [3-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, scratch assay, and invasion assay. The results indicated that AgNPs inhibit the migration of A549 cells. The synthesized AgNPs showed MIC values of 12.5 µg/mL against Chromobacterium violaceum (C. violaceum) and 25 µg/mL against Pseudomonas aeruginosa (P. aeruginosa), which demonstrated their antibacterial abilities. Biological compounds that disable the QS system are being investigated as potential strategies for preventing bacterial infections. Thus, we analyzed the potential effectiveness of synthesized AgNPs in inhibiting QS-regulated virulence factors and biofilm formation in both strains of bacteria. In C. violaceum, the synthesized AgNPs significantly inhibited both violacein (85.18% at 1/2 × MIC) and acyl homoserine lactone (78.76% at 1/2 × MIC). QS inhibitory activity was also demonstrated in P. aeruginosa at a sub-MIC concentration (1/2 × MIC) by a reduction in pyocyanin activity (68.83%), total protease (68.50%), LasA activity (63.91%), and LasB activity (56.40%). Additionally, the exopolysaccharide production was significantly reduced in both C. violaceum (65.79% at 1/2 × MIC) and P. aeruginosa (57.65% at 1/2 × MIC). The formation of biofilm was also significantly inhibited at 1/2 × MIC in C. violaceum (76.49%) and in P. aeruginosa (65.31%). Moreover, a GC–MS analysis confirmed the presence of different classes of bioactive phytochemical constituents present in the leaf extract of E. sativa. On the basis of our results, we conclude that biologically synthesized AgNPs showed numerous multifunctional properties and have the potential to be used against human cancer and bacterial biofilm-related infections.

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.

Assessment of probiotic efficacy and anticancer activities of Lactiplantibacillus plantarum ESSG1 (MZ683194.1) and Lactiplantibacillus pentosus ESSG2 (MZ683195.1) isolated from dairy products

Resistance to antibiotics is on the rise, and its indiscriminate usage has resulted in human and animal management constraints. In the research for an innovative treatment to diminish antimicrobial resistance, lactic acid bacteria (LAB) throw light on diminishing this problem in public health. As a result, this paper looked at the efficacy of LAB isolates and their active metabolites to combat pathogens, reduce antibiotic use in clinical settings, and explore the anticancer potential of 8 strains of LAB isolated from dairy products. Antifungal and antibacterial potential of LAB isolates against selected crop pathogenic fungi and food pathogenic bacteria had been estimated. Results revealed that all isolates exert antioxidant efficacy relating to DPPH, NO scavenging ability, reducing power, superoxide anion, hydroxyl radical, and anti-lipid peroxidation potential. Additionally, 12B isolate exert the highest anticancer upshot with IC₅₀ values of 43.98 ± 0.4; 36.7 ± 0.6, 43.1 ± 0.8, and 35.1 ± 0.3 μg/ml, versus Caco-2, MCF-7, HepG-2, and PC3 cell lines respectively, whereas 13B isolate significantly had the highest selectivity index between peripheral blood mononuclear cells (PBMCs) and the tested human cancer cell lines compared to 5-fluorouracil. 13B was the most apoptosis-dependent death inducer for all human cancer cell lines besides exerting the lowest percentage of apoptosis against PBMCs suggesting its safety against PBMCs. The most promising strains 12B and 13B were identified by 16S rRNA sequencing as Lactiplantibacillus plantarum ESSG1 (MZ683194.1) and Lactiplantibacillus pentosus ESSG2 (MZ683195.1). LAB and their extracts are superb substitutive, safe, and efficient antimicrobial, antioxidant, and antitumor curative agents.

Lactiplantibacillus plantarum-Derived Biosurfactant Attenuates Quorum Sensing-Mediated Virulence and Biofilm Formation in Pseudomonas aeruginosa and Chromobacterium violaceum

Quorum sensing (QS) controls the expression of diverse biological traits in bacteria, including virulence factors. Any natural bioactive compound that disables the QS system is being considered as a potential strategy to prevent bacterial infection. Various biological activities of biosurfactants have been observed, including anti-QS effects. In the present study, we investigated the effectiveness of a biosurfactant derived from Lactiplantibacillus plantarum on QS-regulated virulence factors and biofilm formation in Pseudomonas aeruginosa and Chromobacterium violaceum. The structural analogues of the crude biosurfactant were identified using gas chromatography–mass spectrometry (GC–MS). Moreover, the inhibitory prospects of identified structural analogues were assessed with QS-associated CviR, LasA, and LasI ligands via in silico molecular docking analysis. An L. plantarum-derived biosurfactant showed a promising dose-dependent interference with the production of both violacein and acyl homoserine lactone (AHL) in C. violaceum. In P. aeruginosa, at a sub-MIC concentration (2.5 mg/mL), QS inhibitory activity was also demonstrated by reduction in pyocyanin (66.63%), total protease (60.95%), LasA (56.62%), and LasB elastase (51.33%) activity. The swarming motility and exopolysaccharide production were also significantly reduced in both C. violaceum (61.13%) and P. aeruginosa (53.11%). When compared with control, biofilm formation was also considerably reduced in C. violaceum (68.12%) and P. aeruginosa (59.80%). A GC–MS analysis confirmed that the crude biosurfactant derived from L. plantarum was a glycolipid type. Among all, n-hexadecanoic acid, oleic acid, and 1H-indene,1-hexadecyl-2,3-dihydro had a high affinity for CviR, LasI, and LasA, respectively. Thus, our findings suggest that the crude biosurfactant of L. plantarum can be used as a new anti-QS/antibiofilm agent against biofilm-associated pathogenesis, which warrants further investigation to uncover its therapeutic efficacy.

Postbiotics of Lactobacillus casei target virulence and biofilm formation of Pseudomonas aeruginosa by modulating quorum sensing

Among various anti-virulence aspects, the efficacy of the bioactive constituents of probiotics, referred to as postbiotics, to affect quorum sensing (QS)-modulated signaling of pathogens, is considered as a safe natural approach. The present study investigated the potential QS-inhibitory activity of lyophilized postbiotics from Lactobacillus casei sub sp. casei PTCC 1608 on virulence phenotypes and biofilm of two strains and three clinical isolates of Pseudomonas aeruginosa. The effect of L. casei postbiotics (LCP) at sub-minimum inhibitory concentration on the expression of QS genes including lasR/I, rhlR/I, pqsA, pqsR and virulence genes including pelF (pellicle/biofilm glycosyltransferase PelF), lasB (elastase LasB) and toxA (exotoxin A) was evaluated. The viability of mouse fibroblastic NIH/3T3 cell line treated with sub-MIC_S of LCP was also investigated. Postbiotics were characterized using mass spectrometry-based analyses. The QS-attenuation effect of pure lactic acid as the major constituent of LCP was determined on P. aeruginosa strains. Neutralized postbiotics and crude bacteriocin did not exhibit any antibacterial activity. It was found that sub-MIC_S of LCP could more drastically attenuate the tested virulence phenotypes and biofilm formation than lactic acid. Biofilm inhibition was confirmed using scanning electron microscopy. The rhlI, rhlR, and pelF genes were down-regulated after treatment with LCP. No cytotoxicity effect was observed on NIH/3T3 cell line. The findings demonstrated that postbiotics of L. casei could reduce the virulence and biofilm development of P. aeruginosa and suggested a novel safe natural source for the expansion of anti-virulence treatments.

Synergistic Antimicrobial Effect of Lactiplantibacillus plantarum and Lawsonia inermis Against Staphylococcus aureus

Purpose

The developed resistance of pathogenic microorganisms towards the currently used antimicrobial agents requires the fast search for newer potent antimicrobials. One of the most important ways to combat the previously mentioned disaster is the use of natural alternatives like medicinal plants. Our study aimed to estimate the anti-inflammatory property, and antibacterial effects of probiotics Lactiplantibacillus plantarum and ethanol extracts of Lawsonia inermis leaves against Staphylococcus aureus when they were used separately or collectively as synergism.

Material and Methods

Experimentally induced infected wound model in mice was created and divided into 10 groups then treated for two days by L. plantarum and L. inermis individually or in combination, followed by biochemical assays. The antibacterial, anti-inflammatory, and wound healing activity were evaluated through histopathological sections taken before and after treatment.

Results

Our results revealed that L. plantarum and L. inermis mixture could inhibit growth of S. aureus and decrease the minimal inhibitory concentration (MIC) of L. plantarum to 2 mg/mL. The mixture decreased level of both interleukin 6 (IL-6) and interferon-alpha (TNF-α) to a level near the normal uninfected group. Histopathological study showed that animals treated with both L. plantarum and L. inermis had achieved almost 90% healing.

Conclusion

These results suggest that L. plantarum and L. inermis mixture has synergistic effect on healing of infected wound.

The role of microbiota-derived postbiotic mediators on biofilm formation and quorum sensing-mediated virulence of Streptococcus mutans: A perspective on preventing dental caries

Dental caries is not only one of the most prevalent diseases worldwide, but also a public health problem, undoubtedly. Among the various types of cariogenic bacteria, Streptococcus mutans is considered to be the major etiological pathogen of dental caries. The present study aimed to assess the influence of microbiota-derived postbiotic mediators (PMs) on the pathogenesis of dental caries. Within this aim, the antibacterial (agar diffusion method) and antibiofilm (crystal violet assay) characteristics of PMs derived from Lactiplantibacillus plantarum EIR/IF-1, Lactiplantibacillus curvatus EIR/DG-1, and Lactiplantibacillus curvatus EIR/BG-2 against S. mutans (ATCC 25175) were analyzed. According to the results, PM of the strain EIR/IF-1, isolated from infant feces showed the highest inhibitory effect (pH-dependent). Besides, sub-MIC doses of all PMs eliminated the biofilm formation following the co-incubation and pre-treatment assays. The reduction of cell viability and notable changes in biofilm formation was also confirmed both on glass coverslips and ex vivo human tooth surfaces by confocal laser scanning microscopy and scanning electron microscopy. Moreover, sub-MIC values of PMs down-regulated the expression of gtfC, comA, and comX, without any significant growth inhibition. Organic acids, fatty acids, and vitamins in PMs were also reported. Overall, these findings indicated the possible preventive roles of microbiota-derived PMs for the pathogenesis of dental caries.

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.

Bioprospecting Antimicrobials from Lactiplantibacillus plantarum: Key Factors Underlying Its Probiotic Action

Lactiplantibacillus plantarum (L. plantarum) is a well-studied and versatile species of lactobacilli. It is found in several niches, including human mucosal surfaces, and it is largely employed in the food industry and boasts a millenary tradition of safe use, sharing a long-lasting relationship with humans. L. plantarum is generally recognised as safe and exhibits a strong probiotic character, so that several strains are commercialised as health-promoting supplements and functional food products. For these reasons, L. plantarum represents a valuable model to gain insight into the nature and mechanisms of antimicrobials as key factors underlying the probiotic action of health-promoting microbes. Probiotic antimicrobials can inhibit the growth of pathogens in the gut ensuring the intestinal homeostasis and contributing to the host health. Furthermore, they may be attractive alternatives to conventional antibiotics, holding potential in several biomedical applications. The aim of this review is to investigate the most relevant papers published in the last ten years, bioprospecting the antimicrobial activity of characterised probiotic L. plantarum strains. Specifically, it focuses on the different chemical nature, the action spectra and the mechanisms underlying the bioactivity of their antibacterial and antiviral agents. Emerging trends in postbiotics, some in vivo applications of L. plantarum antimicrobials, including strengths and limitations of their therapeutic potential, are addressed and discussed.

Topical Delivery of Lactobacillus Culture Supernatant Increases Survival and Wound Resolution in Traumatic Acinetobacter baumannii Infections

Species of Lactobacillus have been proposed as potential candidates for treating wound infections due to their ability to lower pH, decrease inflammation, and release antimicrobial compounds. This study investigated the impact of lactobacilli (Lactobacillus acidophilus ATCC 4356, Lactobacillus casei ATCC 393, Lactobacillus reuteri ATCC 23272) secreted products on wound pathogens in vitro and in a murine wound infection model. Evaluation of 1-5 day lactobacilli conditioned media (CM) revealed maximal inhibition against wound pathogens using the 5-day CM. The minimum inhibitory concentration (MIC) of 5-day Lactobacillus CMs was tested by diluting CM in Mueller-Hinton (MH) broth from 0 to 25% and was found to be 12.5% for A. baumannii. Concentrating the CM to 10× with a 3 kDa centrifuge filter decreased the CM MIC to 6.25-12.5% for A. baumannii planktonic cells. Minimal impact of 5-day CMs was observed against bacterial biofilms. No toxicity was observed when these Lactobacillus CMs were injected into Galleria melonella waxworms. For the murine A. baumannii wound infection studies, improved survival was observed following topical treatment with L. acidophilus ATCC 4356 or L. reuteri ATCC 23272, while L. reuteri ATCC 23272 treatment alone improved wound resolution. Overall, this study suggests that the topical application of certain Lactobacillus species byproducts could be effective against gram-negative multi-drug resistant (MDR) wound pathogens, such as A. baumannii.

A New Approach to Harness Probiotics Against Common Bacterial Skin Pathogens: Towards Living Antimicrobials

In this study, the potential of certain lactic acid bacteria—classified as probiotics and known to be antimicrobially active against pathogens or food-poisoning microorganisms—was evaluated with respect to their activity against bacterial skin pathogens. The aim of the study was to develop a plaster/bandage for the application of inhibitory substances produced by these probiotics when applied to diseased skin. For this purpose, two Streptococcus salivarius strains and one Lactobacillus plantarum were tested for production of antimicrobials (bacteriocin-like substances) active against Gram-positive and Gram-negative pathogens using established methods. A newly designed membrane test ensured that the probiotics produce antimicrobials diffusible through membranes. Target organisms used were Cutibacterium acnes, Staphylococcus aureus, and Pseudomonas aeruginosa. Moreover, the L. plantarum 8P-A3 strain was tested against additional bacteria involved in skin disorders. The Lactobacillales used were active against all potential skin pathogens tested. These probiotics could be enclosed between polymer membranes—one tight, the other permeable for their products, preserved by vacuum drying, and reactivated after at least three months storage. Importantly, the reactivated pads containing the probiotics demonstrated antibacterial activity on agar plates against all pathogens tested. This suggests that the probiotic containing pads may be topically applied for the treatment of skin disorders without the need for a regular antibiotic treatment or as an adjunctive therapy.

Colonization and immunoregulation of Lactobacillus plantarum BF_15, a novel probiotic strain from the feces of breast-fed infants

Immunosuppression is a manifestation imbalance in the immune system, often during unhealthy states. In recent years, lactic acid bacteria (LAB) have been found to be important components of the body's innate immune system, and indispensable to maintaining normal immune function. Lactobacillus plantarum BF_15, a novel strain isolated from the feces of breast-fed infants, which has shown potential as an immunomodulator in vitro. In the present study, with the Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) based on RNA-polymerase beta subunit encoding gene (rpoB) to analyze the colonization of L. plantarum BF_15 in the intestine of mice. In addition, Lactobacillus rhamnosus GG (LGG) as a positive control strain, by measuring immune-related indexes and the diversity of intestinal microbiota, the effects of BF_15 on immunoregulation and intestinal microbiota dysbiosis were investigated to elucidate whether the attenuation of immunosuppression is related to the modulation of intestinal microbiota. Results did indeed support this notion that BF_15 did colonize murine intestines well, in which it could still be detected in mice feces 14 days after stopping the probiotic administration. Moreover, BF_15 found to protect mice against reduction in the levels of several immune-related indicators, including the thymus and spleen indexes, splenic lymphocyte proliferation, toe swelling degree, serum hemolysin-antibody level, and macrophage phagocytosis index, triggered by high-dose (200 mg kg-1) intraperitoneal administration of cyclophosphamide (CTX). In addition, the strain was also found to effectively balance intestinal microbiota dysbiosis in the mice. Collectively, these results indicated that L. plantarum BF_15 can not only successfully colonize murine intestines, but also can effectively alleviate CTX-induced immunosuppression, once established, by rebalancing the intestinal microbiota. This, therefore, provides strong evidence for the view that BF_15 has the potential to become a highly effective immunomodulating probiotic in human microbiota as well.

Health-Promoting Role of Lactiplantibacillus plantarum Isolated from Fermented Foods

Fermentation processes have been used for centuries for food production and preservation. Besides the contribution of fermentation to food quality, recently, scientific interest in the beneficial nature of fermented foods as a reservoir of probiotic candidates is increasing. Fermented food microbes are gaining attention for their health-promoting potential and for being genetically related to human probiotic bacteria. Among them, Lactiplantibacillus (Lpb.) plantarum strains, with a long history in the food industry as starter cultures in the production of a wide variety of fermented foods, are being investigated for their beneficial properties which are similar to those of probiotic strains, and they are also applied in clinical interventions. Food-associated Lpb. plantarum showed a good adaptation and adhesion ability in the gastro-intestinal tract and the potential to affect host health through various beneficial activities, e.g., antimicrobial, antioxidative, antigenotoxic, anti-inflammatory and immunomodulatory, in several in vitro and in vivo studies. This review provides an overview of fermented-associated Lpb. plantarum health benefits with evidence from clinical studies. Probiotic criteria that fermented-associated microbes need to fulfil are also reported.

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.

Effects of Natural Products on Bacterial Communication and Network-Quorum Sensing

Quorum sensing (QS) has emerged as a research hotspot in microbiology and medicine. QS is a regulatory cell communication system used by bacterial flora to signal to the external environment. QS influences bacterial growth, proliferation, biofilm formation, virulence factor production, antibiotic synthesis, and environmental adaptation. Through the QS system, natural products can regulate the growth of harmful bacteria and enhance the growth of beneficial bacteria, thereby improving human health. Herein, we review advances in the discovery of natural products that regulate bacterial QS systems.

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.

Efficacy of Using Probiotics with Antagonistic Activity against Pathogens of Wound Infections: An Integrative Review of Literature

The skin and its microbiota serve as physical barriers to prevent invasion of pathogens. Skin damage can be a consequence of illness, surgery, and burns. The most effective wound management strategy is to prevent infections, promote healing, and prevent excess scarring. It is well established that probiotics can aid in skin healing by stimulating the production of immune cells, and they also exhibit antagonistic effects against pathogens via competitive exclusion of pathogens. Our aim was to conduct a review of recent literature on the efficacy of using probiotics against pathogens that cause wound infections. In this integrative review, we searched through the literature published in the international following databases: PubMed, ScienceDirect, Web of Science, and Scopus using the search terms “probiotic” AND “wound infection.” During a comprehensive review and critique of the selected research, fourteen in vitro studies, 8 animal studies, and 19 clinical studies were found. Two of these in vitro studies also included animal studies, yielding a total of 39 articles for inclusion in the review. The most commonly used probiotics for all studies were well-known strains of the species Lactobacillus plantarum, Lactobacillus casei, Lactobacillus acidophilus, and Lactobacillus rhamnosus. All in vitro studies showed successful inhibition of chosen skin or wound pathogens by the selected probiotics. Within the animal studies on mice, rats, and rabbits, probiotics showed strong opportunities for counteracting wound infections. Most clinical studies showed slight or statistically significant lower incidence of surgical site infections, foot ulcer infection, or burn infections for patients using probiotics. Several of these studies also indicated a statistically significant wound healing effect for the probiotic groups. This review indicates that exogenous and oral application of probiotics has shown reduction in wound infections, especially when used as an adjuvant to antibiotic therapy, and therefore the potential use of probiotics in this field remains worthy of further studies, perhaps focused more on typical skin inhabitants as next-generation probiotics with high potential.

Recent Advances in Non-Conventional Antimicrobial Approaches for Chronic Wound Biofilms: Have We Found the 'Chink in the Armor'?

Chronic wounds are a major healthcare burden, with huge public health and economic impact. Microbial infections are the single most important cause of chronic, non-healing wounds. Chronic wound infections typically form biofilms, which are notoriously recalcitrant to conventional antibiotics. This prompts the need for alternative or adjunct ‘anti-biofilm’ approaches, notably those that account for the unique chronic wound biofilm microenvironment. In this review, we discuss the recent advances in non-conventional antimicrobial approaches for chronic wound biofilms, looking beyond standard antibiotic therapies. These non-conventional strategies are discussed under three groups. The first group focuses on treatment approaches that directly kill or inhibit microbes in chronic wound biofilms, using mechanisms or delivery strategies distinct from antibiotics. The second group discusses antimicrobial approaches that modify the biological, chemical or biophysical parameters in the chronic wound microenvironment, which in turn enables the disruption and removal of biofilms. Finally, therapeutic approaches that affect both, biofilm bacteria and microenvironment factors, are discussed. Understanding the advantages and limitations of these recent approaches, their stage of development and role in biofilm management, could lead to new treatment paradigms for chronic wound infections. Towards this end, we discuss the possibility that non-conventional antimicrobial therapeutics and targets could expose the ‘chink in the armor’ of chronic wound biofilms, thereby providing much-needed alternative or adjunct strategies for wound infection management.