The killer phenomenon in yeasts has been revealed to be a multicentric model for molecular biologists, virologists, phytopathologists, epidemiologists, industrial and medical microbiologists, mycologists, and pharmacologists. The surprisingly widespread occurrence of the killer phenomenon among taxonomically unrelated microorganisms, including prokaryotic and eukaryotic pathogens, has engendered a new interest in its biological significance as well as its theoretical and practical applications. The search for therapeutic opportunities by using yeast killer systems has conceptually opened new avenues for the prevention and control of life-threatening fungal diseases through the idiotypic network that is apparently exploited by the immune system in the course of natural infections. In this review, the biology, ecology, epidemiology, therapeutics, serology, and idiotypy of yeast killer systems are discussed.
Twenty-three Lactobacillus strains of dairy origin were evaluated for some functional properties relevant to their use as probiotics. A preliminary subtractive screening based on the abilities to inhibit the growth of microbial pathogens and hydrolyze conjugated bile salts was applied, and six strains were selected for further characterization including survival under gastrointestinal environmental conditions, adhesion to gut epithelial tissue, enzymatic activity, and some safety properties. All selected strains maintained elevated cell numbers under conditions simulating passage through the human gastrointestinal tract, well comparable to the values obtained for the probiotic strain Lactobacillus rhamnosus GG, and were able to adhere to Caco-2 cells to various extents (from 3 to 20%). All strains exhibited high aminopeptidase, and absent or very low proteolytic and strong β-galactosidase activities; none was found to be haemolytic or to produce biogenic amines and all were susceptible to tetracycline, chloramphenicol, erythromycin, ampicillin, and amoxicillin/clavulanic acid. Our results indicate that the Lactobacillus strains analyzed could be considered appropriate probiotic candidates, due to resistance to GIT simulated conditions, antimicrobial activity, adhesion to Caco-2 cell-line, and absence of undesirable properties. They could be used as adjunct cultures for contributing to the quality and health related functional properties of dairy products.
Rat monoclonal yeast killer toxin (KT)-like immunoglobulin M (IgM) anti-idiotypic antibodies (KT-IdAbs) were produced by idiotypic vaccination with a mouse monoclonal antibody (MAb; MAb KT4) that neutralized a Pichia anomala KT characterized by a wide spectrum of antimicrobial activity. The characteristics of the KT-IdAbs were demonstrated by their capacity to compete with the KT to the idiotype of MAb KT4 and to interact with putative KT cell wall receptors (KTRs) of sensitive Candida albicans cells. The internal-image properties of KT-IdAbs were proven by their killer activity against KT-sensitive yeasts. This lethal effect was abolished by prior adsorption of KT-IdAbs with MAb KT4. These findings stressed the potential importance of antibody-mediated immunoprotection against candidiasis and suggested a feasible experimental approach for producing antimicrobial receptor antibodies without purifying the receptor. KT-IdAbs might represent the basis for producing engineered derivatives with a high potential for effective therapeutic antifungal activity. MATERIALS AND METHODS Strains. P. anomala ATCC 96603 (formerly defined as UP 25F) was used for KT production. P. anomala UM3 and C. albicans UP 10, two yeast isolates known to be sensitive to the activity of the P. anomala KT, were also used in this study. These yeasts were subcultured on Sabouraud dextrose agar plates (Difco Laboratories, Detroit, Mich.) and are maintained in sterile distilled water in our fungus collection. KT production. KT was produced by a previously described procedure (21). Briefly, P. anomala ATCC 96603 was grown for 24 h at 25ЊC in Sabouraud broth (Difco) buffered at pH 4.6 with 0.1 M citric acid and 0.2 M sodium phosphate. The supernatant was filtered and concentrated 50 times with Minicon B15 concentrators (Amicon Division, W. R. Grace & Co., Beverly, Mass.). The concentrated KT was tested for killer activity against a recognized sensitive strain by conventional well assay (33) and was refrigerated (4ЊC) until it was used. Animals. Fischer-344 rats (CPA Rot, Roquemaure, France) were used in this study to produce KT-IdAbs. Immunogen. An immunoglobulin G1 (IgG1) MAb (MAb KT4) which neutralized the activity of P. anomala KT against recognized KT-sensitive strains of C. albicans and which was produced by standard procedures as described previ
Two recombinant strains of Streptococcus gordonii, secreting or displaying a microbicidal single-chain antibody (H6), and stably colonizing rat vagina, were used to treat an experimental vaginitis caused by Candida albicans. A post-challenge intravaginal delivery of the H6-secreting strain was as efficacious as fluconazole in rapidly abating the fungal burden. Three weeks after challenge, 75% and 37.5% of the rats treated with the H6-secreting or displaying bacteria, respectively, were cured of the infection, which persisted in 100% of the animals treated with a S. gordonii strain expressing an irrelevant single-chain antibody. Thus, a human commensal bacterium can be suitably engineered to locally release a therapeutic antibody fragment.
scFvKT exerted a microbicidal activity against multidrug resistant bacteria, which may represent the basis for the drug modeling of new antibiotics with broad antibacterial spectra to tackle the emergence of microbial resistance.
The aim of this study was to test the application in vitro of different laser wavelengths at a low fluence in combination or not with proper photosensitizing dyes on Candida albicans biofilm with or without a synthetic killer decapeptide (KP).Candida albicans SC5314 was grown on Sabouraud dextrose agar plates at 37°C for 24 h. Cells were suspended in RPMI 1640 buffered with MOPS and cultured directly on the flat bottom of 96-wells plates. The previously described killer decapeptide KP was used in this study.Three different combinations of wavelengths and dyes were applied, laser irradiation has been performed at a fluence of 10 J/cm 2 . The effect on C. albicans biofilm was evaluated by the XTT assay. Microscopic observations were realized by fluorescence optic microscopy with calcofluor white and propidium iodide.Compared with control, no inhibition of C. albicans biofilm viability was obtained with application of red, blue and green lasers alone or with any combination of red diode laser, toluidine blue and KP. The combined application of blue diode laser with curcumin and/or KP showed always a very significant inhibition, as curcumin alone and the combination of curcumin and KP did, while combination of blue diode laser and KP gave a less significant inhibition, the same obtained with KP alone. The combined application of green diode laser with erythrosine and/or KP showed always a very significant inhibition, as the combination of erythrosine and KP did, but no difference was observed with respect to the treatment with erythrosine alone. Again, combination of green diode laser and KP gave a significant inhibition, although paradoxically lower than the one obtained with KP alone.Treatment with KP alone, while reducing biofilm viability did not cause C. albicans death in the adopted experimental conditions. On the contrary, combined treatment with blue laser, curcumin and KP, as well as green laser, erythrosine and KP led to death most C. albicans cells.The combination of laser light at a fluence of 10 J/cm 2 and the appropriate photosensitizing agent, together with the use of KP, proved to exert differential effects on C. albicans biofilm.
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