Ana Bačić

Probiotics are widely used to support host health by modulating microbial communities and immune–metabolic homeostasis. Such interventions may be particularly relevant in long COVID syndrome, a condition characterized by persistent symptoms, low-grade inflammation, and microbiota alterations following SARS-CoV-2 infection. This study investigated the effects of a multi-strain probiotic on gut microbiota composition and predicted functional potential and biochemical parameters in individuals with long COVID and convalescent participants. Healthy individuals were included as reference controls. In an interventional study, 34 participants received a 12-week probiotic formulation containing Saccharomyces boulardii, Lacticaseibacillus rhamnosus GG, and two Lactiplantibacillus plantarum strains, while 40 served as non-supplemented controls. Fecal microbiota, assessed using 16S rRNA sequencing, and biochemical markers were measured at baseline and post-intervention. Probiotic supplementation induced selective compositional changes without significantly altering overall microbial diversity. Effects were more pronounced in long COVID participants and included enrichment of bacteria associated with metabolic and immune regulation, including Adlercreutzia, Coprococcus, and Eubacterium. Functional prediction analysis identified a probiotic-responsive signature in long-COVID-affected individuals, characterized by enrichment of pathways related to energy metabolism and redox balance. These microbial changes were accompanied by a consistent trend toward reduced inflammatory and hepatic markers. Overall, probiotic intervention demonstrated microbiota-status-dependent potential in long COVID recovery.

Phenolic compounds, abundantly found in medicinal herbs, may promote health by modulating the gut microbiota. Yarrow is a traditional remedy for digestive and non‐gastrointestinal diseases with unexplored interaction with gut microbes. This study aimed to evaluate the effects of yarrow extract and a phenolic mixture comprising apigenin, caffeic, and chlorogenic acids on the gut microbiota using the TIM‐2 in vitro system. The TIM‐2 units were inoculated with fecal samples from healthy individuals and supplemented with test substrates for 72 h. Microbiota composition was assessed by V₃‐V₄ 16S rRNA gene sequencing, while organic acid production was evaluated by GC‐MS. The yarrow extract stimulated probiotic bacteria Lactiplantibacillus, and other abundant and symbiotic gut inhabitants, including Eggerthellaceae, Christensenellaceae, Butyricicoccaceae, and the Eubacterium coprostanoligenes group. The phenolic mixture exerted milder effects on gut microbiota by enhancing the growth of Eggerthellaceae and Collinsella. Looking at the microbial activity, the production of SCFAs, specifically acetic and propionic acids, was increased in the yarrow group. The obtained results highlight the importance of yarrow phenolics in maintaining microbiota balance. The yarrow extract and specific phenolics may modulate the gut microbiota by promoting the growth of SCFA producers and stimulating SCFA synthesis.

Helicobacter pylori eradication is characterized by decreasing successful eradication rates. Although treatment failure is primarily associated with resistance to antibiotics, other unknown factors may influence the eradication outcome. This study aimed to assess the presence of the antibiotics resistance genes in H. pylori and the presence of Candida spp., which are proposed to be endosymbiotic hosts of H. pylori, in gastric biopsies of H. pylori-positive patients while simultaneously assessing their relationship. The detection and identification of Candida yeasts and the detection of mutations specific for clarithromycin and fluoroquinolones were performed by using the real-time PCR (RT-PCR) method on DNA extracted from 110 gastric biopsy samples of H. pylori-positive participants. Resistance rate to clarithromycin and fluoroquinolone was 52% and 47%, respectively. Antibiotic resistance was associated with more eradication attempts (p < 0.05). Candida species were detected in nine (8.18%) patients. Candida presence was associated with older age (p < 0.05). A high rate of antibiotic resistance was observed, while Candida presence was scarce, suggesting that endosymbiosis between H. pylori and Candida may not be a major contributing factor to the eradication failure. However, the older age favored Candida gastric mucosa colonization, which could contribute to gastric pathologies and microbiome dysbiosis.

A thriving community of microorganisms resides in our intestines, forming complex interactions and producing signaling molecules that can affect human physiological processes. Intrinsic and environmental factors modulate the composition of the microbial ecosystem, with diet representing a key factor affecting the formation of gut microbiota. The epidemic of noncommunicable chronic diseases has been associated with the Western diet, which may modulate the gut microbiota, resulting in a detrimental derangement in the microbial community, termed dysbiosis. Dysbiosis may be reverted through dietary interventions and the application of probiotics and prebiotics. Phenolic compounds represent plant-based nutraceuticals, which can be separated into phenolic acids and polyphenols, that exert prebiotic-like effects and may prevent the development of diseases. Besides direct health-promoting activities, beneficial effects of phenolic compounds may be exerted through their interaction with the gut microbiota. A bidirectional relationship between the gut microbiota and phenolic compounds has been observed, as microorganisms are involved in the metabolism of phenolic compounds, whereas phenolic compounds may affect the composition of the microbiota, with selective stimulatory or inhibitory activity towards the growth of microbial members. In this review, insight into the gut microbiota-polyphenols relationship will be given, with a focus on the application of polyphenols for modifying microbiota and promoting health.

The present study aimed to investigate the neuroprotective effects of the vitamin B complex (B1, B2, B3, B5, B6, and B12—VBC), by studying the changes in the femoral nerve, quadriceps muscle, popliteal lymph nodes and gut microbiota in the rat model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). VBC treatment attenuated clinical signs of EAE during the disease, and reduced the duration of EAE thereby contributing to a faster recovery. In VBC-treated EAE rats, a significant decrease in nerve and muscle nuclear density was revealed during the onset period of the disease, while a marked increase was detected at the end of the disease, compared with untreated EAE rats. In the lymph nodes of VBC-treated EAE rats, a fewer number of lymphoid follicles in the cortical area and smaller epithelioid granulomas were detected. The changes in microbiota composition were examined using 16S rRNA gene sequencing and bioinformatics analysis, which revealed the potential of VBC treatment in establishing and/or maintaining gut microbiota homeostasis. Finally, the present study demonstrated that VBC treatment ameliorated the cellular changes in the affected peripheral nerve, muscles innervated by this nerve, and the gut microbiota dysbiosis which occurred during the EAE.