Curdlan, a β-1,3/1,6-glucan found in Alcaligenes faecalis (A. faecalis) wall, activates innate and humoral immunity. The aim of this study is to evaluate whether pretreated rats with A. faecalis A12C could prevent sepsis disturbances and identify the immunomodulatory mechanisms involved. Experiments occurred in two stages: a survival study with 16 rats randomly divided into septic (SC) (n = 8) and septic pretreated (SA) (n = 8) groups and 45 rats divided into four groups: healthy (AGUSAN) (n = 9), septic (AGUIC) (n = 13), septic pretreated (AGUIA) (n = 14), and healthy pretreated (AGUSTO) (n = 9). Sepsis was induced by cecal ligation and puncture after 30 days of A. faecalis A12C pretreatment or without. SA group had a higher survival rate of 58% vs. 16% for SC group (P < 0.05). Overall, AGUIA showed better status than AGUIC (P < 0.01). Higher monocytosis was found in AGUIA and AGUSTO vs. AGUIC and AGUSAN, respectively (P < 0.05). A gradual increase in curdlan fecal concentration was observed in AGUIA during pretreatment. Fecal concentrations of Escherichia coli significantly decreased in AGUIA and AGUSTO. Bacterial load in urine, peritoneal lavage fluid (PLF), and bronchoalveolar lavage fluid (BALF) decreased (P < 0.05) in AGUIA vs. AGUIC. Finally, lower inflammation was observed in serum, BALF, and PLF, with reduced IL-6, IL-10, IL-1β, and TNF-α, along with less damage in lungs and peritoneum in AGUIA vs. AGUIC. These findings suggest the connection between curdlan—produced by A. faecalis A12C—with the immune system and the reduction in severity of experimental sepsis.

Microalgae hold great potential towards pharmaceutical and nutraceutical sectors due to their substantial content of highly functional bioactive compounds. To assess their potential as a sustainable source of valuable products, 10 cyanobacterial and 10 eukaryotic microalgal strains belonging to different taxonomic groups (Chlorophyta, Cyanophyta, Euglenophyta, Heterokontophyta and Rhodophyta) were screened for their biochemical profile, antioxidant and antimicrobial activity against Staphylococcus aureus. Total phenol content and antioxidant activity were positively correlated (r = 0.69, p < 0.01), with the highest values observed in Euglena cantabrica, Haematococcus pluvialis, and Chrysoreinhardia giraudii. HPLC-PAD pigment analysis revealed species-specific profiles, with β,β-carotene as major carotenoid in most cyanobacteria, whereas neoxanthin, violaxanthin and lutein were predominantly present in Chlorophyta, and fucoxanthin was the main carotenoid in C. giraudii, Entomoneis sp. and Isochrysis galbana. Protein content ranged from 9.2 ± 0.4% to 57.6 ± 0.5% with the highest levels in the cyanobacteria Microcystis aeruginosa, Nostoc sp., Cylindrospermum stagnale, Anabaena minutissima, and Arthrospira platensis. Multivariate analysis differentiated cyanobacteria and eukaryotes based on their fatty acid profiles. Organic extracts from 15 species showed inhibitory effects against S. aureus with MIC50 < 1024 µg/mL. The eukaryotes Entomoneis sp., C. giraudii, I. galbana, Picochlorum sp. and the cyanobacteria C. stagnale and Nodularia sp. exhibited the strongest inhibitory effects on bacterial growth. In conclusion, E. cantabrica and C. giraudii stood out for their high antioxidant activity and significant antimicrobial effects, respectively, highlighting their potential as valuable sources of bioactive compounds.

Major depressive disorder pathophysiology involves complex gut-brain axis interactions, yet the systemic non-neurochemical impacts of selective serotonin reuptake inhibitors re-main poorly defined. This study evaluated the multidimensional effects of chronic fluoxe-tine administration in Sprague-Dawley rats. Male rats received fluoxetine (10 mg/kg/day) or water for 60 days, followed by behavioral phenotyping, fecal microbiological quantifi-cation, serum biochemistry, complete blood count analysis, and immunohistochemical assessment of the immediate-early gene product c-Fos (cellular proto-oncogene protein) in the striatum. Fluoxetine treatment significantly reduced immobility time in the forced swim test, whereas object recognition memory deteriorated without alterations in anxie-ty-like behavior. Pharmacological intervention markedly depleted fecal bacterial popula-tions and significantly decreased serum vitamin D concentrations. Hematologically, treated animals exhibited significant reductions in total leukocytes, red blood cells, and platelets, alongside elevated hematocrit and mean corpuscular volume. Concurrently, c-Fos-positive neuronal activation increased significantly within the striatal nucleus ac-cumbens. In conclusion, chronic fluoxetine exposure induces profound systemic disrup-tion, altering gut microbial homeostasis, depleting vitamin D, and modulating peripheral blood profiles while enhancing central striatal neuronal plasticity. These findings under-score the necessity of monitoring gut-brain axis integrity during prolonged antidepressant therapy.