Vaccines
What are advantages of DNA/RNA vaccines
Cell mediated immunity without using live vector
No anti-vector response (multiple inoculations)
No potential for reversion to virulence
rapid synthesis and testing
What are organic acids made of? sold as?
Wide range from plant and microbial origin - Malic, fumaric, sorbic, citric, formic, lactic, butyric, propionic, acetic
Often sold as salts - potassium acetate vs. acetic acid
What is sodium chlorate? why it is used?
Feed inclusion reduces populations of E. coli and salmonella in pigs, cattle, poultry
Enterobacteriaceae family can respire anaerobically using nitrate - dissimilatory nitrate reductase = reduces nitrate to nitrite, also reduces chlorate to chlorite, chlorite accumulates in cell and is toxic
Pre-harvest food safety = diet/water inclusion 24-48 hours prior to slaughter
Post-weaning E.coli control in pigs
Mechanisms of action
How does competitive exclusion: nutrients work
probiotics utilize available nutrients competing with pathogens
- all microorganisms require iron for growth (some probiotics are able to bind iron at the cell surface to exclude it from pathogens), spore forming probiotics / yeasts may use up oxygen (less oxygen for pathogens many of which can use oxygen)
How do commercial products face skepticism?
mechanisms of action are poorly understood
- Many possible mechanisms but for most no specific information
- companies/universities report trials in which the probiotic reduced pathogen colonization and or increased performance; not trials that failed
- early products may not have been as efficacious as current products increasing skepticism
- complex and dynamic gut microbiota difficult to study; no ideal microbiome established
- With undefined mechanisms conditions under which product will be successful are unknown
- significant marketing
What are disadvantages of DNA/RNA vaccines
Need to identify protective antigen
DNA vaccines more stable but difficult to get nuclear localization
RNA highly suseptible to degredation
Expensive
What is the variable anti-microbial activity of organic acids
Gram negative bacteria may be more susceptible
Bacteriostatic or bactericidal
different acids often used in combination
What are some microbial fermentation products? (hint AA)
Crystalline amino acids, synthetic vitamins, enzymes
Fermentation on corn starch, sugar beet molasses - L-Lysine, L-Threonine, L-tryptophan, DL-Methionine, vitamin B2 (riboflavin), phytase, beta-glucanases, pentosanases
Purified from organisms selected or modified for maximum synthesis
Mechanisms of action
How does competitive exclusion: antimicrobial effects work
Many species produce antibiotic compounds. For example bacteriocins are secreted proteins which may limit growth of competitive bacteria
Some bacteria deconjugate bile acids which are bacteriostatic and this also could decrease the cholesterol level
Others produce hydrogen peroxide, nitric oxide, etc.
what are probiotics target application and routes of application?
Target - Prophylactic disease control, performance improvement (healthy animals grow faster with less feed), Human food safety
Route - feed (must survive processing, storage, feed trough & yeast/bacillus dominate food animal products), water, spray on
What is a type of heterologous vaccine
Smallpox vaccination - viccinia virus
Considered eradicated but soldiers in the middle east require vaccination as precaution against bioterrorism
What is the efficacy against salmonella with Formic acid + lactic acid in pigs
vs.
The efficacy against salmonella with acetic, lactic, and formic acid with broilers
No effect of 0.4% formic + 0.4% lactic acid in salmonella challenged pigs
Inclusion of selected acids at 0.5% in drinking water of broilers on feed withdrawal prior to processing
What is the definition of a probiotic?
Live microorganisms which when administered in adequate amounts confer a health benefit on the host
Mechanisms of action
How does aggregation work
probiotic microorganisms may coat pathogens preventing their attachment and facilitating removal by peristalsis
Coaggregate - more than one probiotic bacterial species could involved
What does the timing of application for probiotics look like
Target before colonization established - may have lifetime effects = birth (spray on for chicks), in dams feed (for neonate via dam feces)
During periods of increased infectious disease - associated with disruption of "normal" microbiota = weaning, transport
What are adjuvants?
slow release of antigen/activate antigen presenting cells
stimulation of cellular vs humoral immunity
Why don't organic acids reach the hind gut? How can we make them?
Highly soluble and absorptive so they don't make it through & if they do leave they also leave the SI quickly
Get them to the hind gut through protective coatings or fermentable fibre
The intestinal microbiota & pathogen resistance steps are? (with mice)
Germ free animals are rapidly colonized by pathogens when challenged
Salmonella spp. colonize germ free mice to a level of 1010 cfu per gram in 24 hours. in conventional mice shigella colonize to 103 per gram
Germ free mice can be restored by treating with fresh fecal material - resistance to challenge returns to level of conventional mice
Mechanisms of action
How does immune stimulation work
Activate innate immune mechanisms - increase mucin secretion by goblet cells, increase expression of anti-microbial peptides, decrease epithelial permeability
Activate immune cells and enhance acquired immune response
What are prebiotics? types?
Nonviable compounds which promote growth of beneficial organisms when ingested - lack many of the commercialization difficulties in supplying live probiotics
Oligosaccharides - mannan-oligosaccharides, fructo-oligosaccharides, inulin, galacto-oligosaccharides, resistant starch & unavailable to host but function as - preferential energy substrate for beneficial bacteria increasing their relative abundance
What things lead to t and b cell activation
Saponins, oil emulsions, aluminum salts, host defense peptides, cytokines, MAMPS
-> Ag presentation
-> T and B cell activation
-> acquired immunity
How does microbial origin of organic acids happen
From fermentation of fibre or protected products
Acidification/direct antimicrobial - colon pH 5.0-6.5
Propionate, butyrate (tends to replace glucose as the energy source in the distal gut) - down regulate SPI-1 virulence genes in salmonella
Butyrate - colonocyte energy source, inflammatory = receptors in colonocytes, epithelial growth = receptors in colonocytes
Mechanisms of action
How does competitive exclusion: space work
Adhesion to epithelium is necessary for pathogens to become established and cause infection
preoccupation of sites by probiotics prevent pathogen attachment
Mechanisms of action
How does direct vs. indirect mechanisms work
Direct - probiotic organism "directly" contributes to any of the mechanisms described above
Indirect - Probiotic shifts microbial profile towards other species or groups of species that subsequently drive any of the mechanisms described above
What does transgenic probiotic success require?
High expression level
reasonable protein stability
ability to secrete if necessary for mechanism of action
ability to colonize in high number