Metagenomic and metatranscriptomic profiling of Lactobacillus casei Zhang in the human gut

Little is known about the replication and dynamic transcription of probiotics during their “passenger” journey in the human GI tract, which has therefore limited the understanding of their probiotic mechanisms. Here, metagenomic and metatranscriptomic sequencing was used to expose the in vivo expression patterns of the probiotic Lactobacillus casei Zhang (LcZ), which was compared with its in vitro growth transcriptomes, as well as the dynamics of the indigenous microbiome response to probiotic consumption. Extraction of the strain-specific reads revealed that replication and transcripts from the ingested LcZ were increased, while those from the resident L. casei strains remained unchanged. Mapping of all sequencing reads to LcZ genome showed that gene expression in vitro and in vivo differed dramatically. Approximately 39% of mRNAs and 45% of sRNAs of LcZ well-expressed were repressed after ingestion into human gut. The expression of ABC transporter genes and amino acid metabolism genes was induced at day 14 of ingestion, and genes for sugar and SCFA metabolism were activated at day 28 of ingestion. Expression of rli28c sRNA with peaked expression during the in vitro stationary phase was also activated in the human gut; this sRNA repressed LcZ growth and lactic acid production in vitro. However, the response of the human gut microbiome to LcZ was limited and heterogeneous. These findings implicate the ingested probiotic has to change its transcription patterns to survive and adapt in the human gut, and the time-dependent activation patterns indicate highly dynamic cross-talk between the probiotic and human gut microbes.

PSVIII-8 Effect of Lactobacillus Casei Zhang on E. coli induced injury of blood and milk barrier in dairy cow

Bovine mastitis is one of the major diseases which directly affects the milk production performance and it causes huge economic losses in the dairy industry. Bacterial infection is the main risk factor of bovine mastitis and the antibiotic therapy is the primary choice to control the disease. However, persistence use of antibiotic increases the incidence of bacterial resistance and traces of antibiotic residues in animal products. Lactobacillus casei Zhang is one of the probiotics with multiple biological functions, which has certain bacteriostatic effect on pathogenic microorganism. The purpose of this study was to explore the effect of Lactobacillus casei Zhang (L. casei Zhang) on the prevention of E. coli-induced milk-blood barrier damage. Bovine mammary epithelial cells (BMECs) were used to establish a milk-blood model and Control group (PBS), E. coli group, and L. casei Zhang pretreatment plus E. coli group were set up respectively. The results showed that: L. casei Zhang could significantly reduce the increase of LDH release caused by E. coli treatment (P< 0.05). And it can also significantly reduce the decrease of transmembrane resistance of monolayer cells caused by E. coli treatment (P< 0.05). In addition, L. casei Zhang could significantly reduce the expression of tight junction proteins ZO-1, Claudin-1, Claudin-4 and Occludin (P < 0.05). In conclusion, L. casei Zhang could effectively improve the damage of the blood-milk barrier caused by E. coli and could protect BMECs during bacterial infection.

PSVIII-18 Protective effect of Lactobacillus Casei Zhang on E. coli induced mastitis in mice

Mastitis is an acute, obvious and harmful clinical disease in mammals. It is also one of the productive diseases with high incidence, rapid epidemic and great economic loss in dairy farming. Antibiotics are the first choice for the treatment of infectious mastitis, but the long-term use of antibiotics in large quantities will lead to the emergence of antibiotic residues and bacterial resistance, which is harmful to the health of both human and animals. As a potential substitute of antibiotics, Lactobacillus has great potential in the control of pathogenic microorganisms. The purpose of this study was to explore the effect of Lactobacillus casei Zhang (L. Casei Zhang) on the prevention of E. coli-induced mastitis in mice and its protective effect on the damage of the blood and milk barrier. Intramammary administration of E. coli was used to establish a mouse mastitis model. Control group (PBS), E. coli administration group, and L. casei Zhang pretreatment plus E. coli administration group were set up respectively and the mammary gland samples were collected for analysis. The results showed that: L. casei Zhang could significantly reduce the degree of breast tissue damage and the content of inflammatory factors TNF-α，IL-6 and IL-1β (P < 0.05). In addition, the expression of tight junction proteins ZO-1, Claudin-3 and Occludin in the mammary gland tissues of mice was significantly promoted (P < 0.05). In conclusion, intramammary administration of L. casei Zhang could effectively reduce the inflammation of the mouse mammary gland induced by E. coli, and this protection is achieved by promoting the expression of the blood-milk barrier tight junction proteins.