Isolation of derivatives from the food-grade probiotic <i>Lactobacillus johnsonii</i> CNCM I-4884 with enhanced anti- <i>Giardia</i> activity

Giardiasis, a widespread intestinal parasitosis affecting humans and animals, is a growing concern due to the emergence of drug-resistant strains of <i>G. intestinalis</i>. Probiotics offer a promising alternative for preventing and treating giardiasis. Recent studies have shown that the probiotic <i>Lactobacillus johnsonii</i> CNCM I-4884 inhibits <i>G. intestinalis</i> growth both <i>in vitro</i> and <i>in vivo</i>. This protective effect is largely mediated by bile salt hydrolase (BSH) enzymes, which convert conjugated bile acids (BAs) into free forms that are toxic to the parasite. The objective of this study was to use adaptive evolution to develop stress-resistant derivatives of <i>L. johnsonii</i> CNCM I-4884, with the aim of improving its anti-<i>Giardia</i> activity. Twelve derivatives with enhanced resistance to BAs and reduced autolysis were generated. Among them, derivative M11 exhibited the highest <i>in vitro</i> anti-<i>Giardia</i> effect with enhanced BSH activity. Genomic and proteomic analyses of M11 revealed two SNPs and the upregulation of the global stress response by SigB, which likely contributed to its increased BAs resistance and BSH overproduction. Finally, the anti-<i>Giardia</i> efficacy of M11 was validated in a murine model of giardiasis. In conclusion, our results demonstrate that adaptive evolution is an effective strategy to generate robust food-grade bacteria with improved health benefits.