Lactobacillus paracasei modulates the immune system of Galleria mellonella and protects against Candida albicans infection

Influence of the use of complete denture adhesives on microbial adhesion and biofilm formation by single- and mixed-species

Objectives

To verify whether the Ultra Corega Cream and Corega Strip Denture Adhesive adhesives interfere in the microbial adhesion and biofilm formation by Candida albicans and Lactobacillus casei in single- and mixed-species settings, and observe whether synergistic or antagonistic relationships between these species occur.

Methods

Specimens made from heat-polymerized acrylic resin (Lucitone 550) were fabricated (n = 144) with a circular shape and standardized roughness (3.0 μm ±0.3 Ra) and were divided into three groups: Without Adhesive (WA), with Ultra Corega Cream adhesive (CA) and Corega Strips adhesive (SA). These groups were divided into three subgroups each: C. albicans single-species, L. casei single-species and C. albicans with L. casei (mixed-species). Microbial adhesion and biofilm formation assays were performed in duplicate at four distinct experimental times (n = 8 per experimental condition). The amount of each microorganism on the surfaces of the specimens was observed by counting of the Colony Forming Units (CFU) per substrate. Additional specimens were characterized by Scanning Electron Microscopy (SEM), with 18 specimens being used in this analysis (n = 18), 2 per experimental condition (n = 2). Two-way ANOVA and Tukey’s test for multiple comparisons were employed, using α≤0.05.

Results

L. casei (mixed-species) adhered more on the WA substrate than the CA, while C. albicans (single- and mixed-species) adhered more on the SA. C. albicans, both single- and mixed-species adhered more than the L. casei (single- and mixed-species), regardless of the substrate. L. casei (single-species) formed more biofilm on the WA, but in its mixed cultivation, it had no difference of growth among the tested situations. C. albicans (single- and mixed-species) formed more biofilm on the SA than the CA, and the fungus formed more biofilm when compared to L. casei. In general, whenever a species was compared in its single- and mixed-species situation, no statistically significant difference was observed. SEM of biofilm formation assays demonstrated that L. casei single-species WA formed more biofilm than when the adhesives tested were used, and C. albicans (both single- and mixed-species) formed more biofilm on the SA than on the CA.

Conclusions

(1) The two denture adhesives tested increased the adhesion of C. albicans but not of L. casei; (2) biofilm formation by C. albicans (single- and mixed-species) was increased on the SA; (3) Relations of synergism or antagonism was not observed between the two microorganisms studied.

Methodologies for in vitro and in vivo evaluation of efficacy of antifungal and antibiofilm agents and surface coatings against fungal biofilms

Unlike superficial fungal infections of the skin and nails, which are the most common fungal diseases in humans, invasive fungal infections carry high morbidity and mortality, particularly those associated with biofilm formation on indwelling medical devices. Therapeutic management of these complex diseases is often complicated by the rise in resistance to the commonly used antifungal agents. Therefore, the availability of accurate susceptibility testing methods for determining antifungal resistance, as well as discovery of novel antifungal and antibiofilm agents, are key priorities in medical mycology research. To direct advancements in this field, here we present an overview of the methods currently available for determining (i) the susceptibility or resistance of fungal isolates or biofilms to antifungal or antibiofilm compounds and compound combinations; (ii) the in vivo efficacy of antifungal and antibiofilm compounds and compound combinations; and (iii) the in vitro and in vivo performance of anti-infective coatings and materials to prevent fungal biofilm-based infections.

Draft Genome Sequence of Lactobacillus paracasei DUP 13076, Which Exhibits Potent Antipathogenic Effects against Salmonella enterica Serovars Enteritidis, Typhimurium, and Heidelberg

Lactobacillus paracasei DUP 13076 demonstrates antagonistic effects against the foodborne pathogens Salmonella enterica serovars Enteritidis, Typhimurium, and Heidelberg in coculture and in vitro experiments. Here, we report the draft genome sequence of Lactobacillus paracasei DUP 13076, which has a circular chromosome of 3,048,314 bp and a G+C content of 46.3%.

Lactobacillus paracasei 28.4 reduces in vitro hyphae formation of Candida albicans and prevents the filamentation in an experimental model of Caenorhabditis elegans

The objective of this study was to evaluate the influence of microbe-microbe interactions to identify a strain of Lactobacillus that could reduce the filamentation of Candida albicans ATCC 18804 using in vitro and in vivo models. Thus presenting a probiotic effect against the fungal pathogen. First, we analyzed the ability of 25 clinical isolates of Lactobacillus to reduce filamentation in C. albicans in vitro. We found that L. paracasei isolate 28.4 exhibited the greatest reduction of C. albicans hyphae (p = 0.0109). This reduction was confirmed by scanning electron microscopy analysis. The influence of C. albicans filamentation was found to be contributed through reduced gene expression of filament associated genes (TEC1 and UME6). In an in vivo study, prophylactic provisions with L. paracasei increased the survival of Caenorhabditis elegans worms infected with C. albicans (p = 0.0001) by 29%. Prolonged survival was accompanied by the prevention of cuticle rupture of 27% of the worms by filamentation of C. albicans, a phenotype that is characteristic of C. albicans killing of nematodes, compared to the control group. Lactobacillus paracasei isolate 28.4 reduced the filamentation of C. albicans in vitro by negatively regulating the TEC1 and UME6 genes that are essential for the production of hyphae. Prophylactic provision of Lactobacillus paracasei 28.4 protected C. elegans against candidiasis in vivo. L. paracasei 28.4 has the potential to be employed as an alternative method to control candidiasis.

Clinical strains of Lactobacillus reduce the filamentation of Candida albicans and protect Galleria mellonella against experimental candidiasis

Candida albicans is the most common human fungal pathogen and can grow as yeast or filaments, depending on the environmental conditions. The filamentous form is of particular interest because it can play a direct role in adherence and pathogenicity. Therefore, the purpose of this study was to evaluate the effects of three clinical strains of Lactobacillus on C. albicans filamentation as well as their probiotic potential in pathogen-host interactions via an experimental candidiasis model study in Galleria mellonella. We used the reference strain Candida albicans ATCC 18804 and three clinical strains of Lactobacillus: L. rhamnosus strain 5.2, L. paracasei strain 20.3, and L. fermentum strain 20.4. First, the capacity of C. albicans to form hyphae was tested in vitro through association with the Lactobacillus strains. After that, we verified the ability of these strains to attenuate experimental candidiasis in a Galleria mellonella model through a survival curve assay. Regarding the filamentation assay, a significant reduction in hyphae formation of up to 57% was observed when C. albicans was incubated in the presence of the Lactobacillus strains, compared to a control group composed of only C. albicans. In addition, when the larvae were pretreated with Lactobacillus spp. prior to C. albicans infection, the survival rate of G. mellonela increased in all experimental groups. We concluded that Lactobacillus influences the growth and expression C. albicans virulence factors, which may interfere with the pathogenicity of these microorganisms.

Immunomodulatory effects and anti-Candida activity of lactobacilli in macrophages and in invertebrate model of Galleria mellonella

Due to the growing number of multi-resistant Candida spp., adjuvant treatments that may help combat these fungal pathogens are relevant and useful. This study evaluated the immunomodulation and anti-Candida activity of Lactobacillus rhamnosus (LR), Lactobacillus acidophilus and Lactobacillus paracasei suspensions, either single- or multiple-strain, in mouse macrophages (RAW 264.7) and Galleria mellonella (GM). Mouse macrophages were activated by different lactobacilli suspensions and challenged with C. albicans (CA). Tumor necrosis factor (TNF)-α, interleukin IL-1β, IL-6 and IL-17 production and cell viability were investigated. LR was the best suspension for stimulating all evaluated cytokines and thus was used in subsequent in vivo assays. Two C. albicans clinical strains, CA21 and CA60, were then added to the GM assays to further confirm the results. LR suspension was injected into the larvae 24 h before challenging with CA. Survival curve, CFU per larva and hemocytes were counted. In the GM, the LR suspension increased the survival rate and hemocyte counts and decreased the CFU per larva counts for all groups. Lactobacilli suspensions presented strain-dependent immunomodulation; however, single suspensions showed better results. Anti-Candida activity was demonstrated by decreased Candida counts in the GM with the use of LR.

Immunomodulatory effect of photodynamic therapy in Galleria mellonella infected with Porphyromonas gingivalis

Porphyromonas gingivalis is an important pathogen in the development of periodontal disease. Our study investigated if the treatment with antimicrobial photodynamic therapy (aPDT) that employs a nontoxic dye, followed by irradiation with harmless visible light can attenuate the experimental infection of P. gingivalis in Galleria mellonella. Firstly, different concentrations of P. gingivalis ranging from 10² to 10⁶ cells/larva were injected into the animal to obtain a lethal concentration. Next, the following groups of G. mellonella infected with P. gingivalis were evaluated: inoculation of the photosensitizer and application of laser (P + L+), inoculation of physiologic solution and application of laser (P-L+), inoculation the photosensitizer without laser (P + L-) and inoculation of physiologic solution without Laser (P-L-). The effects of aPDT on infection by P. gingivalis were evaluated by survival curve analysis and hemocytes count. A lethal concentration of 10⁶ cells/larva was adopted for evaluating the effects of aPDT on experimental infection with P. gingivalis. We found that after 120 s of PDT application, the death of G. mellonella was significantly lower compared to the control groups (p = 0.0010). Moreover, the hemocyte density in the P+L+ group was increased by 9.6 × 10⁶ cells/mL (2.62-fold increase) compared to the infected larvae with no treatment (L-P- group) (p = 0.0175). Finally, we verified that the aPDT led to a significant reduction of the number of P. gingivalis cells in G. mellonella hemolymph. In conclusion, PDT application was effective against P. gingivalis infection by increasing the survival of G. mellonella and was able to increase the circulating hemocytes indicating that PDT activates the G. mellonella immune system.