# Long-Term Treatment with Alcaligenes faecalis A12C Improves Host Resistance to Pathogens in Septic Rats: Possible Contribution of Curdlan-Like Immune Trainer

## TL;DR

Long-term treatment with Alcaligenes faecalis A12C boosts immune resistance in septic rats, possibly through curdlan-like compounds.

## Contribution

This study demonstrates that pretreatment with A. faecalis A12C improves survival and reduces inflammation in septic rats.

## Key findings

- Pretreated rats had a 58% survival rate compared to 16% in untreated septic rats.
- Pretreatment reduced bacterial load and inflammation markers like IL-6 and TNF-α in septic rats.
- Fecal curdlan levels increased during pretreatment, correlating with immune improvements.

## Abstract

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.

The online version contains supplementary material available at 10.1007/s12602-024-10252-0.