Incidence of Saccharomyces cerevisiae fungemia in hospitalised patients administered Saccharomyces boulardii probiotic

Unlocking the power of postbiotics: A revolutionary approach to nutrition for humans and animals

Postbiotics, which comprise inanimate microorganisms or their constituents, have recently gained significant attention for their potential health benefits. Extensive research on postbiotics has uncovered many beneficial effects on hosts, including antioxidant activity, immunomodulatory effects, gut microbiota modulation, and enhancement of epithelial barrier function. Although these features resemble those of probiotics, the stability and safety of postbiotics make them an appealing alternative. In this review, we provide a comprehensive summary of the latest research on postbiotics, emphasizing their positive impacts on both human and animal health. As our understanding of the influence of postbiotics on living organisms continues to grow, their application in clinical and nutritional settings, as well as animal husbandry, is expected to expand. Moreover, by substituting postbiotics for antibiotics, we can promote health and productivity while minimizing adverse effects. This alternative approach holds immense potential for improving health outcomes and revolutionizing the food and animal products industries.

A Repertoire of the Less Common Clinical Yeasts

Invasive fungal diseases are a public health problem. They affect a constantly increasing number of at-risk patients, and their incidence has risen in recent years. These opportunistic infections are mainly due to Candida sp. but less common or rare yeast infections should not be underestimated. These so-called "less common" yeasts include Ascomycota of the genera Candida (excluding the five major Candida species), Magnusiomyces/Saprochaete, Malassezia, and Saccharomyces, and Basidiomycota of the genera Cryptococcus (excluding the Cryptococcus neoformans/gattii complex members), Rhodotorula, and Trichosporon. The aim of this review is to (i) inventory the less common yeasts isolated in humans, (ii) provide details regarding the specific anatomical locations where they have been detected and the clinical characteristics of the resulting infections, and (iii) provide an update on yeast taxonomy. Of the total of 239,890 fungal taxa and their associated synonyms sourced from the MycoBank and NCBI Taxonomy databases, we successfully identified 192 yeasts, including 127 Ascomycota and 65 Basidiomycota. This repertoire allows us to highlight rare yeasts and their tropism for certain anatomical sites and will provide an additional tool for diagnostic management.

Saccharomyces boulardii prophylaxis for targeted antibiotics and infectious indications to reduce healthcare facility-onset Clostridioides difficile infection

BACKGROUND

Probiotic prophylaxis for Clostridioides difficile infection (CDI) is controversial stemming from deficits in strain and disease specificity considerations and concern for adverse effects. Here risk for healthcare facility-onset CDI (HO-CDI) dependent on concomitant antibiotic and infectious indication is assessed to identify opportunities for targeted prophylaxis.

METHODS

Retrospective matched-cohort study from January 2016 through March 2019. Patient-admissions administered high risk antibiotics were categorized by Saccharomyces boulardii administration and matched 1:1 to non-recipients. Unadjusted and adjusted HO-CDI risk estimated using Cox proportional hazards regression.

RESULTS

S. boulardii administration was associated with 48% risk reduction for HO-CDI compared to non-recipients (aHR 0.52, 95% CI: 0.31-0.87). Patient-admissions administered antibiotics and S. boulardii for a pneumonia indication exhibited a 57% reduction in risk for HO-CDI (aHR 0.43, 95% CI: 0.19-0.95). Administration of S. boulardii with ceftriaxone was associated with a 76% reduced risk of HO-CDI (aHR 0.24, 95% CI: 0.11-0.53) compared to ceftriaxone without S. boulardii, number needed to treat of 100.

CONCLUSIONS

S. boulardii administration is associated with a significant HO-CDI risk reduction for inpatients receiving antibiotics associated with CDI. Institutions interested in targeted use of S. boulardii to limit potential adverse effects may consider prophylaxis for inpatients with pneumonia or receiving ceftriaxone.

Modulation of yeast Erg1 expression and terbinafine susceptibility by iron bioavailability

Ergosterol is a specific sterol component of yeast and fungal membranes. Its biosynthesis is one of the most effective targets for antifungal treatments. However, the emergent resistance to multiple sterol‐based antifungal drugs emphasizes the need for new therapeutic approaches. The allylamine terbinafine, which selectively inhibits squalene epoxidase Erg1 within the ergosterol biosynthetic pathway, is mainly used to treat dermatomycoses, whereas its effectiveness in other fungal infections is limited. Given that ergosterol biosynthesis depends on iron as an essential cofactor, in this report, we used the yeast Saccharomyces cerevisiae to investigate how iron bioavailability influences Erg1 expression and terbinafine susceptibility. We observed that both chemical and genetic depletion of iron decrease ERG1 expression, leading to an increase in terbinafine susceptibility. Deletion of either ROX1 transcriptional repressor or CTH1 and CTH2 post‐transcriptional repressors of ERG1 expression led to an increase in Erg1 protein levels and terbinafine resistance. On the contrary, overexpression of CTH2 led to the opposite effect, lowering Erg1 levels and increasing terbinafine susceptibility. Although strain‐specific particularities exist, opportunistic pathogenic strains of S. cerevisiae displayed a response similar to the laboratory strain. These data indicate that iron bioavailability and particular regulatory factors could be used to modulate susceptibility to terbinafine.

Update of the list of QPS-recommended microbiological agents intentionally added to food or feed as notified to EFSA 16: suitability of taxonomic units notified to EFSA until March 2022

The qualified presumption of safety (QPS) approach was developed to provide a regularly updated generic pre‐evaluation of the safety of microorganisms, intended for use in the food or feed chains, to support the work of EFSA's Scientific Panels. The QPS approach is based on an assessment of published data for each agent, with respect to its taxonomic identity, the body of relevant knowledge, safety concerns and occurrence of antimicrobial resistance. Safety concerns identified for a taxonomic unit (TU) are, where possible, confirmed at the species/strain or product level and reflected by ‘qualifications’. In the period covered by this statement, no new information was found that would change the status of previously recommended QPS TUs. Of the 50 microorganisms notified to EFSA in October 2021 to March 2022 (inclusive), 41 were not evaluated: 10 filamentous fungi, 1 Enterococcus faecium, 1 Clostridium butyricum, 3 Escherichia coli and 1 Streptomyces spp. because are excluded from QPS evaluation, and 25 TUs that have already a QPS status. Nine notifications, corresponding to seven TUs were evaluated: four of these, Streptococcus salivarius, Companilactobacillus formosensis, Pseudonocardia autotrophica and Papiliotrema terrestris, being evaluated for the first time. The other three, Microbacterium foliorum, Pseudomonas fluorescens and Ensifer adhaerens were re‐assessed. None of these TUs were recommended for QPS status: Ensifer adhaerens, Microbacterium foliorum, Companilactobacillus formosensis and Papiliotrema terrestris due to a limited body of knowledge, Streptococcus salivarius due to its ability to cause bacteraemia and systemic infection that results in a variety of morbidities, Pseudonocardia autotrophica due to lack of body of knowledge and uncertainty on the safety of biologically active compounds which can be produced, and Pseudomonas fluorescens due to possible safety concerns.

Heme Oxygenase-1 (HMX1) Loss of Function Increases the In-Host Fitness of the Saccharomyces 'boulardii' Probiotic Yeast in a Mouse Fungemia Model

The use of yeast-containing probiotics is on the rise; however, these products occasionally cause fungal infections and possibly even fungemia among susceptible probiotic-treated patients. The incidence of such cases is probably underestimated, which is why it is important to delve deeper into the pathomechanism and the adaptive features of S. ‘boulardii’. Here in this study, the potential role of the gene heme oxygenase-1 (HMX1) in probiotic yeast bloodstream-derived infections was studied by generating marker-free HMX1 deletion mutants with CRISPR/Cas9 technology from both commercial and clinical S. ‘boulardii’ isolates. The six commercial and clinical yeasts used here represented closely related but different genetic backgrounds as revealed by comparative genomic analysis. We compared the wild-type isolates against deletion mutants for their tolerance of iron starvation, hemolytic activity, as well as kidney burden in immunosuppressed BALB/c mice after lateral tail vein injection. Our results reveal that the lack of HMX1 in S. ‘boulardii’ significantly (p < 0.0001) increases the kidney burden of the mice in most genetic backgrounds, while at the same time causes decreased growth in iron-deprived media in vitro. These findings indicate that even a single-gene loss-of-function mutation can, surprisingly, cause elevated fitness in the host during an opportunistic systemic infection. Our findings indicate that the safety assessment of S. ‘boulardii’ strains should not only take strain-to-strain variation into account, but also avoid extrapolating in vitro results to in vivo virulence factor determination.