Animal & Avian Sciences Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2741
Browse
3 results
Search Results
Item ANTAGONISTIC MECHANISM OF METABOLITES FROM LACTOBACILLUS CASEI AGAINST FOODBORNE ENTEROHEMORRHAGIC ESCHERICHIA COLI(2022) Aditya, Arpita; Biswas, Debabrata; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Enterohemorrhagic Escherichia coli O157: H7 (EHEC), a foodborne enteropathogen, remains a significant public health concern since its discovery in 1982. With an incredibly low infectious dose (10-100 bacteria), this pathogen can cause self-limiting diarrhea, vomiting, and abdominal cramps. However, more complicated disease conditions such as bloody diarrhea or hemolytic colitis have been known to develop depending on the serotype involved in the infection, and on immune status and/or age of the patients. Due to its Shiga toxin (Stx) production ability, EHEC infection may lead to a kidney-related problem known as hemolytic uremic syndrome (HUS), which requires advanced medical care. Unlike other bacterial illnesses, therapeutic administration of antibiotics to treat EHEC infections is not recommended due to their controversial association with Stx production. As a result, only preventative/prophylactic and immune-supportive strategies are followed for EHEC infections. Using the antibacterial properties of probiotic bacteria and the metabolites they produce are promising alternative strategies for preventing EHEC infections. We have targeted the probiotic bacteria Lactobacillus casei to determine the mechanism of this alternative strategy. In our study, we have executed microbiological, molecular, chromatographic, and metagenomic approaches to determine the antagonistic mechanisms of action of their metabolites, specifically conjugated linoleic acid (CLA) produced by Lactobacillus casei, against the growth and metabolism of EHEC. The metabolites of wild-type L. casei (LCwt) were augmented by supplementing it with a prebiotic-like dietary component, namely peanut flour (PF) (LCwt+PF), while another LCwt was also genetically engineered (LCCLA) to over convert CLA from linoleic acid (LA). These modifications showed effective results in controlling EHEC both in vitro and in ex vivo conditions. Total metabolites present in cell-free culture supernatant (CFCS) of LCwt, LCwt+PF, and LCCLA were able to control the growth of EHEC without negatively hampering the relative abundance of Firmicutes and Bacteroidetes present in rumen fluid (RF). Among these CFCSs, CFCSCLA exerted the most desirable outcome by eliminating EHEC. In vitro studies demonstrated that, a lower concentration of purified CLA worked synergistically with other metabolites of LCwt and augmented their inhibitory activity against EHEC. The orchestrated effect of metabolites has been observed to downregulate the virulence genes, disrupt the cell membrane, interfere with cell division, and damage their genomic DNA. The probable effect of these metabolites, specifically CLA, on Stx production and neutralization was also investigated by assessing host cell cytotoxicity. Total metabolites of Lactobacillus spp. as well as CLA itself, showed improvement in cell survivability when exposed to Stx. Our findings established a ground to explore the effect of specific metabolites obtained from probiotic bacteria in control and prevention of EHEC. The findings also showed a promising association of purified CLA in neutralizing Stx which can be further explored to use it in therapeutic purposes.Item Effect of Air on Rumen Gas Production(2021) Rha, Rachel Youngah; Kohn, Richard A; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Ruminants may swallow air as they eat and ruminate throughout the day. However, it is unclear as to how the introduction of oxygen impacts fermentation pathways, bacteria, and yeast within this mostly anaerobic environment. Therefore, the focus of this thesis was to study air’s impact on rumen fermentation and to determine if probiotics could offset air’s impact on digestibility. An in vitro analysis of air and probiotics indicated the main effect of air decreased digestibility, the main effect of probiotics had variable effects, and probiotics had significant interactions with air. The interactions suggested yeast employing a potential alternative pathway with the introduction of oxygen. Utilizing published literature, a static and dynamic mathematical model was built to further analyze digestibility, gas composition, and uptake of oxygen within the rumen. Future studies will further develop this model with in vivo studies to further interpretation and understanding of rumen fermentation’s complex system.Item The Effects of Tryptophan and Probiotic Treatment on Behavior and Production Parameters of Laying Hens(2021) Bonilla Carrero, Paola Ivette; Dennis, Rachel L; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Dietary supplementation can impact behavior expression through microorganism’s activity in the gut microbiome and influence productivity in animal husbandry. Adding supplements to production animals’ diet can impact behaviors and productivity via gut-brain axis activity. We investigated the effects of either probiotic or antibiotic supplementation in addition to the effects of additional tryptophan (Trp) on overall behavior and production parameters. White Leghorn chickens (n=12) were supplemented with six dietary treatments in a 2 x 3 factorial design: probiotics (1 x 109 CFU/L) or the antibiotic erythromycin (125 mg/L) in combination with either normal (0.16%) or high (0.48%) Trp in drinking water. Results indicate that probiotics with tryptophan increased locomotion (P = 0.04), social (P = 0.04), and eating behavior (P = 0.02). Antibiotics with tryptophan increased fat pad (P = 0.04) and heart weight (P = 0.04). Supplementation affected behavioral expression of normal, comfort, and pecking behavior, potentially impacted by metabolic competition at the level of the gut microbiome.