Midterm 2 Flashcards
Epidemiology
Study of the distribution and determinants of health-related states to events and the application of this study to the control of diseases and other health problems
Outbreak
An incident in which 2 or more persons experienced a similar illness after ingestion of a common food
Case
1 individual experiences illness after ingestion of an incriminated food
Reasons for underestimation
Recognition of infection
Don’t seek medical attention
Need officials to investigate
Need resources, money
Food available for testing
Factors contributing to unknown etiology
Must seek medical attention
Contaminated food unavailable for testing
Long incubation period
Identification of cause is dependent on detection methods
Food recovered → nothing isolated → virus or toxin
Need state and fed resources to collect data/investigate/report
Foodborne disease
Any illness resulting from the consumption of food contaminated with one or more disease producing agents
Infection
A disease state caused by presence of viable, usually multiplying organisms at the site of inflammation
successful persistence of the pathogen, usually by multiplication on or within host tissues
Intoxication
A disease state caused by exposure to a toxic chemical that is not mediated immunologically and is not primarily the result of a genetic deficiency
Metabolic food disorder
Food intolerance resulting from genetically inherited defect in the ability to metabolize a food component
Food allergies
An abnormal response of the immune system to one or more specific foods or components in foods
Mediated through IgE antibody
Allergen severity factors
Individual
Amount of food ingested
Length of time since previous exposure
Idiopathic illness
Response to a food with an unknown cause
Ex: MSG
Why do future projections show an increase in foodborne illness
Demographics
Food preference
Technology
Global market
Water shortage
Microbes (adaption/evolution)
Microbial challenges
Spores
Low infectious dose
Unknown
Detection
Psychotropic
Evolution
At risk Population
Immunocompromised
Very young and old
Chronic illness
Pregnant women
Transplant recipients
AIDS patients
Why are some people more susceptible
Immune system
Environment
Previous exposure
Dietary restrictions
Mouth defenses
Saliva
Enzymes (lysozyme)
Antibodies
Stomach defenses
HCl (pH 1.8 - 2.2)
Pepsin
Duodenum defenses
Bile ducts
Antimicrobial step (kills microbes)
How do pathogens bypass the gastric phase?
When stomach is full (hide in matrix)
Rapid gastric emptying
Neutralization or decrease in acidity by food/illness
Protection by food component (protein/fat)
Small intestine defenses
Other microbes
Antimicrobial factors (lysosome, bile, pancreatic secretions)
Large intestine defenses
Other microbes
Microflora produce mucus (limit penetration)
Digestive enzymes
Bile
Peristalsis
Involuntary muscle structures
Push food in the right direction
Limit time microbe has to find a binding spot, bind, replicate
Innate immunity characteristics
Includes phagocytes, antimicrobial peptides
Rapid response (hours)
Fixed set of components
Limited # of specificities
Constant during response
Adaptive immunity characteristics
Includes B and T cells
Slow response (days to weeks)
Variable
Numerous highly selective specificities
Improve during response
Recognition of specific microbial agents
Leading causes of death
- Diseases of the heart
- Cancer
- Covid
- Accidents
- Stroke
- Chronic respiratory diseases
- Alzheimer’s
- Diabetes
High cost of foodborne illness due to
- Medical care
- Investigation
- Recalls
- Loss of productivity
- Loss of business
Cause of most cases of illness (estimated)
Viruses
Bacteria close behind
Cause of most cases of illness (reported)
Bacterial
Host defenses (summary)
Physical barriers
Mouth
Peristalsis
Mucin
Normal flora
Stomach
Lamina propria
Thin layer of connective tissue
Below epithelium
Contains antimicrobials: lymphocytes, plasma cells, macrophages, mast cells, leukocytes
M cells
Specialized epithelial cells of lymphoid tissue
Transport antigens from lumen to immune system
Allergies (immune system)
Allergen presented to B cell → produce IgE
IgE associates with mast cells → release mediators
Causes symptoms of allergy
Villi in small intestine
Increase surface area and increase absorption
Goblet cells produce mucin layer
Pathogens colonize crypts
Phagocytosis
- Phagosome recognizes PAMP
- Engulf PAMP
- Phagosome fuses with lysosome
- Lysosome dumps enzymes
Proteases, lipases, lysozyme, free radicals = antimicrobials
Goal is to kill pathogen - Microbe degrades
- Dump debris
Lymphocytes
Recognize and respond to any microbial pathogen
Adaptive immunity
Type of leukocytes
T Cells
aid in presentation of antigen to B cells
B cells
create memory cells
Identify self vs nonself
Use MHC
M Cell mechanism
Engulf antigen
Transport to receiving cells (macrophages)
Antigens not modified
Present to other cells
React to epitope (if modified, misinform immune system)
Dendritic cells
Prime immune system
Antigen presentation
Help with self vs nonself
Arthritis
Antigen on bacteria similar to that of muscle tissue
Why can’t we out evolve pathogens
Reproductive rates of humans vs microbes play a key role in race for survival
Microbes reproduce, mutate faster
Immune system can’t predict evolution of microbes
Multiple immune evasion mechanisms have arisen in pathogens
Causes or risk increase
At risk populations
Concomitant infections
Stress
Consumption of antibiotics
Consumption of antacids
Consumption of fatty foods containing pathogens
Nutritional deficiencies
Poor hygiene
Microbes face
Mucous membranes
Harbor scavenger cells
IgA antibodies
Cells and substances that attack invaders
Phagocytes, antimicrobial peptides
Antibodies and cells
Pathogen
a microorganism that has the capacity to
cause disease in a particular host
Disease
an infection that causes significant overt
damage to the host
Virulence
Degree of pathogenicity of a microbe, or the relative ability of a microbe to cause disease
Virulence Factor
components or traits of an
organism that contribute to pathogenicity
Characteristics of foodborne pathogens
- Viable in living organism
- Must survive passing through low pH in stomach, enzymes, bile salts
- Compete with resident microflora
- Establish itself in GI lumen or other tissue to multiply/persist
- Penetrate mucosal barrier and reach target side (if systemic)
Categories of virulence factors
Attachment
Invasion
Evasion
Essential nutrient
Toxins
Secretory systems
Adhesion
Bind to receptors on host cell
Pili, fimbriae
Adhere to extracellular matrix components (collagen, IgE)
Contribute to specificity to host or tissues
Survive phagocytes
Degrade phagosome (escape and grow in cytoplasm)
Prevent acidification of phagosome and fusion with lysosome
Neutralize reactive oxygen species
Degrade lysosomal proteins
Resistant to lysosome enzymes
Evasion
Ig Protease
Polysaccharide capsule (inhibit phagocytosis)
Bind host proteins
Antigenic variation of surface component
Essential nutrient
Iron tightly bound by high affinity proteins in host
Bind proteins or produce compounds that can bind iron
Toxins
Cause damage
Induce host responses
Kill macrophages
Toxin targets
Membranes
Ribosomes
Secondary signal pathways
Secretion systems
Transport of cytoplasmic proteins to other location
Type 3 secretory system
Triggered by contact with host cell
Virulence proteins injected into host cell cytoplasm
Regulation of virulence factors
Expression linked to environmental signals
Global regulators control expression of genes
Pathogenicity island
Contain multiple virulence genes
Flanked by direct repeats, insertion sequence elements
On chromosome or plasmid
G/C content differs from host
Incubation period
Time from ingestion to onset of symptoms
Intoxication → hours
Infection → days to weeks
O antigen
lipopolysaccharides
H antigen
flagella
K antigen
capsule
Detection
Agglutination assay (antibody based)
PCR
EPEC pedastal formation
Intimate association
form pedestals
Inject tir and effector proteins
ETEC ST toxin
Heat stable
Small peptides
Mimic native intestinal hormone
Binds to guanylate cyclase and activates enzyme
ETEC LT toxin
Related to cholera toxin
Subunit cleaved to A1 and A2 fragments
B subunit in toxin specificity
A subunit ribosylated protein (Interferes in secondary G protein signaling pathways)
HUS
Destroy red blood cells
Acute kidney failure
Need blood transfusions, dialysis
Detection of EHEC
DNA target
PCR
Antibodies (immunological)
IMS
Horizontal gene transfer
Transduction (virus)
Transformation (uptake of free DNA)
Conjugation (plasmid mediated)
Distinguish pathotypes
Antigen
Sequencing
Biochemical characteristics
Niche Filling
Consequences for eliminating microbes
Vaccine eliminated Pullorum serovar from chickens → S. enteritidis filled the gap
Competitive exclusion
Two species competing for the same limited resource can’t coexist at a constant population
Infectious dose affected by
Serotype
Strain
Type of food
Host factors
Phase variation
Switching of production of surface antigens in some cells within a population
Prophage
Phage incorporates into host chromosome
Can replicate and reproduce
Trigger → come out of chromosome → go into lytic cycle
Isolate bacteriophage
Test sample before pouring
Mix with host bacterium
Phage specific to host bacteria → lytic → kill surrounding cells
Called plaque assay
GBS
Weakness
Paralysis
B cells generate antibodies
Antibody similar to myelin sheath
Destroy protective covering of nerves
Can’t transmit signal to muscle
Due to cell surface antigens
