title: Risks associated with high-dose Lactobacillus rhamnosus in an Escherichia coli model of piglet diarrhoea: intestinal microbiota and immune imbalances.
abstract: Probiotic could be a promising alternative to antibiotics for the prevention of enteric infections; however, further information on the dose effects is required. In this study, weanling piglets were orally administered low- or high-dose Lactobacillus rhamnosus ACTT 7469 (10(10) CFU/d or 10(12) CFU/d) for 1 week before F4 (K88)-positive Escherichia coli challenge. The compositions of faecal and gastrointestinal microbiota were recorded; gene expression in the intestines was assessed by real-time PCR; serum tumour necrosis factor-α (TNF-α) concentrations and intestinal Toll-like receptor 4 (TLR4) were detected by ELISA and immunohistochemistry, respectively. Unexpectedly, high-dose administration increased the incidence of diarrhoea before F4(+)ETEC challenge, despite the fact that both doses ameliorated F4(+)ETEC-induced diarrhoea with increased Lactobacillus and Bifidobacterium counts accompanied by reduced coliform shedding in faeces. Interestingly, L. rhamnosus administration reduced Lactobacillus and Bifidobacterium counts in the colonic contents, and the high-dose piglets also had lower Lactobacillius and Bacteroides counts in the ileal contents. An increase in the concentration of serum TNF-α induced by F4(+)ETEC was observed, but the increase was delayed by L. rhamnosus. In piglets exposed to F4(+)ETEC, jejunal TLR4 expression increased at the mRNA and protein levels, while jejunal interleukin (IL)-8 and ileal porcine β-defensins 2 (pBD2) mRNA expression increased; however, these increases were attenuated by administration of L. rhamnosus. Notably, expression of jejunal TLR2, ileal TLR9, Nod-like receptor NOD1 and TNF-α mRNA was upregulated in the low-dose piglets after F4(+)ETEC challenge, but not in the high-dose piglets. These findings indicate that pretreatment with a low dose of L. rhamnosus might be more effective than a high dose at ameliorating diarrhoea. There is a risk that high-dose L. rhamnosus pretreatment may negate the preventative effects, thus decreasing the prophylactic benefits against potential enteric pathogens. Our data suggest a safe threshold for preventative use of probiotics in clinical practice.
authors: College of Veterinary Medicine, China Agricultural University, Beijing, China.
authors: Xiao-Qiong
authors: XQ
authors: Li
authors: Yao-Hong
authors: YH
authors: Zhu
authors: Hong-Fu
authors: HF
authors: Zhang
authors: Yuan
authors: Y
authors: Yue
authors: Zheng-Xing
authors: ZX
authors: Cai
authors: Qing-Ping
authors: QP
authors: Lu
authors: Lu
authors: L
authors: Zhang
authors: Xiao-Gang
authors: XG
authors: Weng
authors: Fan-Jian
authors: FJ
authors: Zhang
authors: Dong
authors: D
authors: Zhou
authors: Jin-Cai
authors: JC
authors: Yang
authors: Jiu-Feng
authors: JF
authors: Wang
mesh_terms: D000818:Animals; D003106:Colon / Q000276:immunology / Q000382:microbiology; D016207:Cytokines / Q000276:immunology; D003967:Diarrhea; D004195:Disease Models, Animal; D004306:Dose-Response Relationship, Immunologic; D054307:Enterotoxigenic Escherichia coli / Q000276:immunology*; D004927:Escherichia coli Infections / Q000276:immunology* / Q000473:pathology / Q000517:prevention & control; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology; D007082:Ileum / Q000276:immunology / Q000382:microbiology; D052201:Lacticaseibacillus rhamnosus / Q000276:immunology*; D008297:Male; D053474:Nod1 Signaling Adaptor Protein / Q000276:immunology; D013552:Swine; D051195:Toll-Like Receptor 2 / Q000276:immunology; D051217:Toll-Like Receptor 9 / Q000276:immunology
chemical_list: D016207:Cytokines; D053474:Nod1 Signaling Adaptor Protein; D051195:Toll-Like Receptor 2; D051217:Toll-Like Receptor 9