Lactobacillus is a genus of Gram-positive bacteria that are facultative anaerobes or microaerophilic and are commonly found in the human microbiota, especially in the gut, vagina, and mouth. They are well known for their probiotic properties, meaning they can provide health benefits when consumed in adequate amounts.

### Key characteristics: - Shape: Rod-shaped (bacilli). - Gram stain: Positive. - Fermentation: They ferment carbohydrates to produce lactic acid, which helps inhibit the growth of harmful bacteria. - Habitat: Commonly found in fermented foods like yogurt, kefir, sauerkraut, and also as part of the natural flora in the human body. - Health benefits:

1. Promote gut health and aid digestion.
2. Support the immune system.
3. Help prevent and treat vaginal infections.
4. May reduce inflammation and symptoms of IBS (Irritable Bowel Syndrome).

Alterations in the abundance and diversity of Lactobacillus species may affect immune dysregulation, neuroinflammatory responses, anxiety- and depressive-like behaviors, and neuroprotective mechanisms activated in response to TBI.

A study aims to evaluate the protective and preventive effects of Pan-probiotic (PP) treatment on the inflammatory response during both the acute and chronic phases of TBI.

Males and female mice underwent controlled cortical impact (CCI) injury or sham injury. They received a PP mixture in drinking water containing strains of Lactobacillus plantarum, L. reuteri, L. helveticas, L. fermentum, L. rhamnosus, L. gasseri, and L. casei. In the acute group, mice received PP or vehicle (VH) treatment for 7 weeks before TBI, continuing until 3 days post-injury (dpi). In the chronic group, treatment began 2 weeks before TBI and was extended through 35 dpi. The taxonomic microbiome profiles of fecal samples were evaluated using 16S rRNA V1-V3 sequencing analysis, and Short-chain fatty acids (SCFAs) were measured. Immunohistochemical, in situ hybridization, and histological analyses were performed to assess neuroinflammation post-TBI, while behavioral assessments were conducted to evaluate sensorimotor and cognitive functions.

The findings suggest that a 7-week PP administration induces specific microbial changes, including increased abundance of beneficial bacteria such as Lactobacillaceae, Limosilactobacillus, and Lactiplantibacillus. PP treatment reduces lesion volume and cell death at 3 dpi, elevates SCFA levels at 35 dpi, and decreases microglial activation at both time points, particularly in males. Additionally, PP treatment improved motor recovery in males and alleviated depressive-like behaviors in females.

The findings indicate that PP administration modulates microbiome composition, reduces neuroinflammation, and improves motor deficits following TBI, with these effects being particularly pronounced in male mice ¹⁾.