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Food Borne Diseases Food borne illnesses in the USA: ● 1 in 6 people get food poisoning ● Each year foodborne infections result in: ○ 48 million illnesses ○ 128,000 hospitalizations ○ 3,000 deaths ○ Annual health care cost ( 15 billion USD) Food borne illness Globally: ● 600 Million illnesses (1 in10) ● 420,00 deaths ● Children under 5 years of age carry 40% of the disease burden 125,000 deaths every year ● US 110 billion is lost each year in medical expenses Causes of Foodborne illnesses: ● Bacteria ● Viruses ( Norovirus, Hepatitis B virus ) ● Parasites (toxoplasma Gondii) ● Prions (Creutzfeldt-jakob, CJD, neurodegenerative disorder- due to consumption of contaminated meat) ● Toxins (clostridium botulinum) ● Harmful chemicals
● Bacteria (The big 8) ○ Salmonella spp. (~ 1.2 million illnesses in the USA) ○ Campylobacter jejuni (~ 1.5 million illnesses in the USA) ○ Enterohemorrhagic Escherichia coli ○ Staphylococcus aureus ○ Clostridium perfringens (~ 1 million illnesses in the USA) ○ Listeria monocytogenes ○ Clostridium botulinum ○ Vibrio ● Major foodborne diseases:
Food Borne Pathogens: ● Host: ○ Chickens ( Carry salmonella spp, campylobacter jejuni) ○ Cows ( Carry Enteromorrhagic Escherichia coli) ● Food Products: ○ Listeria monocytogenes ● Processing Environment: ○ Listeria monocytogenes
Alternatives to antibiotics in poultry industry: ● Vaccination ● Bacteriophage ● pre/proBiotics ● Phytochemicals Strategies to control foodborne pathogens 2: ● Control of microorganisms in food processing environment ● Control of access of microorganisms ● Control by disinfectants ● Chlorine based sanitizer washing 200 ppm ● Peracetic acids Strategies to control foodborne pathogens 3: ● Control of Access of Microorganisms ● Control by Physical Removal ● Control by heat ● Control by low temperatures ● Control by reduced water activity and Drying ● Control by low pH and organic acids ● Control by Modified Atmosphere ● Control by antimicrobial preservatives and bacteriophages ● Control by irradiation ● Control by novel processing technologies ● Control by a combination of methods (Hurdle concept) Control of foodborne pathogens in humans: ● Traditional approaches: ○ Antibiotics ○ Disrupt bacterial function: ■ Cell wall synthesis ■ DNA rep ■ RNA transcription ■ Protein synthesis ○ Selection pressure modify host endogenous microbiome ○ Resistant pathogens
● Anti-violence approach: ○ Antibiotic alternatives ○ Less selective pressure ○ Preserving host endogenous microbiome ○ No resistant pathogens ○ Disrupted bacterial virulence: ■ Motility ■ Adhesion,invasion,translocation ■ Toxin production ■ Quorum sensing Overall: Background: ● 48 millions illnesses USA, 600 million globally Major Food pathogens: ● Salmonella, Campylobacter jejuni, Listeria monocytogenes, Norovirus, etc. Control Strategies: ● Farm level, processing environments, food products, Humans.
How does bacteria compare in size to other cells/particles? ● Eukaryotic cells are smaller than prokaryotic cells Bacterial Shapes (Morphology) ● Spirilla ● Bacilli ● Cocci Gram Positive Vs Gram negative bacteria: ● Gram positive bacteria stain blue with gram stain ● Gram negative stains red with gram stain ● Gram negative bacteria contain endotoxins in their cell membrane ● Peptidoglycan , also known as murein is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of eubacteria
● Gram positive has thicker peptidoglycan ● Gram negative has thinner peptidoglycan Where does Bacteria Live? ● Bacteria can be free living in the environment (Water,soil, etc) ● Bacteria can live in plants ● Bacteria can live in animals ○ Bacterial and other agents commonly inhibit your body ■ Athletes foot fungus ■ Vaginalflora (bacteria and yeast) ■ Intestinal flora ■ Human papillomavirus ■ Head lice ■ Dental streptococcus ■ Demodex mites ■ Shingles ■ Fossil viruses ■ Staphylococcus Relationships of bacteria to Eukaryotic Organisms: ● Mutualism ○ A relationship in which both species benefit ○ It’s common in nature ○ In microbiology there are many mutualistic bacteria in the gut to aid digestion in both humans and animals ■ Bacteria and Protozoa in the herbivore rumen and large intestine parts of the GI tract breakdown cellulose into volatile fatty acids digestible by the host animal ● Commensalism ○ Is a relationship between species in which one benefits and the other is unaffected. ○ Harmless bacteria on the skin and within intestines prevent harmful bacteria from colonizing (competition). ● Symbiosis ○ Bacteria and host organisms living together with complete dependance on each other. ■ Rhizobacteria that must be in the certain (legume) plant root nodules to survive, and produce nutrients that the plant requires to survive.
● Endotoxins: ○ Lipopolysaccharides (LPS) in the cell wall of gram-negative bacteria produces general systematic symptoms in the host such as: ■ Fever ■ low blood pressure ■ Endotoxic shock ■ Organ failure ■ Death ■ When the cells are disrupted it allows a release of endotoxins into circulation (Endotoxemia) ● Aggressins: ○ Enzymes produced by bacteria that have localized effects enhancing bacterial ability to invade the host. ■ Coagulase ( staphylococcus aureus) causes: ● Blood to clot ● Produces a fibrin coat around bacteria which protect bacteria from host response ● Collagenase and hyaluronidase : enzymes that break down host tissue , allows bacteria to penetrate
Cellular Invasion capabilities: ● Some bacteria enter host cells ● Replicate within a cell and cause cells to burst ● Organism (protozoal agents, viral agents) invade cells ○ Ex. Salmonella spp invade interstitial epithelial cells, disrupting metabolism and ultimately rupture cell, resulting in hot diarrhea How Bacteria invade the immune system: ● Intracellular location ○ ( Brucella ssp, salmonella spp, Mycobacterium spp) ● Slime layer ○ (bacterial groups living together in a protective biofilm) ● S layer ○ (protein layer in the outermost envelope of the cell wall) ○ protects bacteria from pH changes ○ Enzymes contains adhesins that help bacteria stick to host cells ● Antigenic shifting ○ Changing the outer coat proteins to trick immune respons e ( Borrelia b) Factors associated with bacterial virulence: ● Initiating undesirable immune response: ○ Molecular mimicry leading to autoimmune disease ■ Similarity of bacterial surface antigen to normal protein in the body results in the immune system mounting an immune response that attacks a normal body component. ● Developing of circulating Immune complexes: ○ Soluble antigens produced which bind to antibodies in the bloodstream and are deposited in tissues, such as kidney, causing disease ● Overstimulation of immune response to infection leading to excess inflammation
Issues to be considered for vaccine development: ● Choice of adjuvants ○ Depends on if you want a primary T-cell or B-cell response ● Routes of administration ○ IM,SQ, intranasal,needle-free (patches) ● Booster Vaccinations and schedule ○ Animal producers prefer fewer vaccinations and animal handling ○ Young parents prefer fewer vaccinations for their children also. ● Specific Host responses (using transcriptomics) ○ Paired with pathogens changes during course of infection Types Of Vaccines Currently Available: ● Whole cell inactivated vaccines ○ Killed whole cell virus or bacteria ○ The entire repertoire of antigen is presented for immune stimulation ○ The entire organisms, killed by heat or chemical methods (formalin, acetone, phenol) ○ Unable to replicate in the host but retain antigenically and will induce a protective response. ○ Don’t generate as good a protective immunity as live vaccines but they are very safe ○ No concern to reversion to virulence ○ Very amenable to combinations, very economically significant ● Live attenuated vaccines ○ The virus or bacteria is in a weakened state (attenuated) so its unable to cause any disease ○ Develop strong and long lived protective immunity ○ Advantages of Live attenuated vaccines: ■ May elicit broader immune response ■ May require fever doses ■ Longer lasting protection ○ Disadvantages of live attenuated vaccines: ■ Potential issues of reversion to virulence ■ Most require a cold-chain for storage ( therefore may be difficult for developing nations)
○ Examples: ■ Polivores - live oral (sabin’s) ■ Rubella - German measles ■ Vibrio cholerae strai n- Texas star ■ Bacille Calmette - Guerin (TB) ● Subunit vaccines ○ Requires prior knowledge regarding the subunit’s role in pathogenesis ○ Gives strong, protective immunity but requires a booster vaccination ○ Safe and no possibility reversion of virulence ○ Antigens are produced by purification from the pathogen directly or by recombinants mean ■ Comparative whole genome sequencing and transcriptomics combined with assessment of host immune responses greatly inform the final vaccine constructs. ● Combination Vaccines ○ Meaning two or more vaccines delivered in a single inoculation ○ So like (DPT: diphtheria/pertussis/tetanus) MMR ( measles-mumps-rubella) ○ Each individual's component must be recommended for administration at the same age. ○ Each must be stable and acceptable in terms of physical interactions with each other. ○ Each vaccine in the combination must be as effective in combination as it is individually ○ Advantages: ■ Fewer inoculations/fewer trips to the doctor ■ Less traumatic to the patient ● Viral Vector vaccines ○ These use modified viruses to deliver protective antigens ○ Examples: ■ Rabies G protein- vaccinia based ■ Aenviriuse based: replication- deficient induced full spectrum of immune response ■ Avipoxvirus: An avian pox virus strongly host restricted to birds ■ Recombinant attenuated salmonella ■ Poliovirus -the attended sabin vaccine strain is used
Parasitic Causes of disease Types of Parasites: ● Nematodes - Roundworms ● Cestodes- Tapeworms ● Trematodes- Flatworms ● Protozoa- ● Arthropods/Arachnids- Insects ( directly cause disease or act as vectors of other agents) Domestic Animal Parasites: ● Most animal species ( including humans) have parasites that can infect only one species, some are not as “species specific” and can infect multiple species. Difference Between Insects Vs. Arachnids: ● Arachnids ○ Arthropoda is a phylum that consists of invertebrates with jointed appendages or legs. ○ They consist of a segmented body with a head, thorax, and abdomen. They also consist of a chitinous exoskeleton. ● Both ○ Insects and arachnids are two classes of the phylum Arthropoda. Some of them live as parasites.
● Difference The main difference between insects and arachnids is that insects have six legs and up to four wings whereas arachnids have eight legs. Direct Vs Indirect Life Cycle: ● Direct Lifecycle: ○ Only one host needed for complete parasitic development (from egg to adult to egg) ● Indirect Life Cycle: ○ More than one host is required for parasite to develop from egg to adult to egg Example Direct life cycle- Whipworms Life cycle of parasites: ● Most of the nematode parasites affecting animals (including humans ) have a direct life cycle.
Haemonchus Contortus (Barber Pole worm) Example: Ruminant roundworms ● Host: ○ Sheep, Goat, cattle ● Site: ○ Abomasum ● Life Cycle: ○ Direct; prepatent period (time from parasite ingestion until eggs shed in feces) 20 days. ● Disease: ○ Worms suck blood and cause anemia ○ Bottle jaw ( edema due to protein loss in blood) ○ DX: clinical signs and fecal floatation (microscopic exam for eggs) Fecal Flotation for the detection of parasitic Ova (eggs) ● Concentration techniques ○ Rely of floatation of eggs, oocyste, and other life cycle stages ○ Concentration allows for a big sample to be examined in short periods of time ○ Flotation method rely on on specific gravity of the parasite material ○ Water SG 1, ○ Most eggs have SG of 1.100-1.200 g/ml Haemoncus Contortus (Barber Pole worm) ● Adult worms in the abomasum ● Bottle jaw in goats Dipylidium spp (cestode/tapeworm example) ● Host: ○ Dog, Cat ● Sites: ○ Small intestines ● Life cycle: ○ Indirect (fleas are intermediate host) ○ Prepatent period 14-21 days
● Disease: ○ Worms can cause weight loss ○ Diarrhea ○ Intestinal obstruction ● Diagnosis: ○ Direct observation fecal flotation of worms Common Dog and Cat Tapeworms: ● Dipylidium Caninum ● Taenia taeniaeformis Termadaodes (flukes): ● Flatworms ● Platyhelminthes Human Trematodiasis (Fluke) ● Animals can be definite hosts of various species of flukes too) ○ Examples ■ Clonorchis Sinensis (601 million at risk) ■ Paragonimus spp (293.8 million at risk) ■ Fasciola spp (91.1 million at risk) ■ Opisthorchus spp (79.8 million at risk) ○ The life cycles: ■ Indirect life cycle ■ This trematode has 2 intermediate host ■ Other trematodes have other intermediate host ○ Tremadosis Complications: ■ Can develop chinese liver fluke ■ Clonorchiasis ● Complications include: ○ Bile stasis ○ Liver abscess ○ Neoplasia (bile duct carcinoma ○ Infections as early as 2 years of age untreated
