IHS 340 Exam 1

The allergy epidemic is the rise in allergic diseases following what?

hygiene improvements

**remember that food allergies and asthma have always existed, but their incidence was initially super low. They gained prevalence once incidence increased

Three notable allergic diseases of the allergy epidemic

• Seasonal allergic rhinitis

• Pediatric Asthma

• Peanut allergy

Relative Sizes of Microorganisms

helminths > protozoa > bacteria > animal viruses

Which microorganism can only be seen with an electron microscope?

viruses

Which microorganism can be seen with the human eye?

helminths

Deadliest pandemics in history include:

measles, black death, HIV/AIDS, smallpox, plague of justinian, spanish flu, typhus, cholera, hong kong flu, third pandemic, *SARS CoV2

What infectious diseases has killed the most people?

tuberculosis

In the past 100 years, the declining death rate caused by Tuberculosis is due to ______ and ______

• rising living standards

• new antibiotics

**small spikers were due to WWI and WW2 (where death rate increased)

Impact of Infectious Diseases on Human Health in 1990 vs 2000 in the US

• In 1990 (pre-hygiene and pre-antibiotics), infectious diseases (eg. influenza & pneumonia, TB, gastroenteritis) were a leading cause of death

• While by 2000, the impact of infectious diseases had significantly decreased, and nonmicrobial diseases (eg. heart disease and cancer) took the lead in mortality rates.

• epidemiological shift!

There is an _____ relationship between the incidence of infectious diseases and the incidence of immune hypersensitivity diseases (autoimmunity & allergy)

inverse

Infection

• invasion of an organism's body tissues by disease-causing agents

• the multiplication or metabolically active persistence of those agents

• and the rxn of host tissues to the infectious agents and any toxic compounds they produce

Infectious Disease

disease results from infection by transmissible agent, which can be passed from host to host, including via abiotic or biotic intermediate

All ____ are _____, BUT not all _______ are _______

All infectious diseases are infections, BUT not all infections are infectious diseases

Is the invasion of bacteria from a splinter considered an infection or an infectious diseases?

infection

Endemic level

Amount of a particular disease that is usually present in a community over a sustained period of time

The endemic level is the (observed/desired) level of disease in a community

observed

A disease may continue at the endemic (observed) level indefinitely if there is no ________ and the level is not high enough to _______ the pool of ___________. Thus the baseline is often regarded as the expected level of disease

• intervention

• deplete

• susceptible persons

Endemic (endemic disease)

the constant presence and/or usual prevalence of a disease or infectious agent in a population w/n a geographic area

Sporadic (endemic disease)

disease occurs infrequently and irregularly

Hyperendemic (endemic disease)

persistent, high levels of disease occurrence

What warrants an epidemiologic investigation?

• Some diseases are so rare in a given population that a single case warrants an epidemiologic investigation (e.g., rabies, plague, polio)

• Other diseases occur more commonly so that only deviations from the endemic levels warrant investigation

Epidemic

(often sudden) increase in number of cases of disease above endemic level for that population in that area

Outbreak

defined like an epidemic but is often used for a more limited geographic area

Cluster

Aggregation of cases grouped in place and time that are suspected to be greater than the expected number (even if that number is unknown)

Pandemic

an epidemic that has spread over several countries or continents, usually affecting a large number of people

True or false: epidemics include non-infectious diseases

TRUE!!

• The previous description of epidemics presumes only infectious agents, but non-infectious diseases such as diabetes and obesity exist in epidemic proportion in the U.S. ... as well as food allergies!!

Allergen

• environmental antigen that typically elicits allergic responses ("hypersensitive immune response") in susceptible individuals

• non-infectious

Antigen

• substance that induces an immune response in the body

• are bound by AB or T lymphocyte antigen receptor

Allergic response

immune system overreaction to a substance that is normally harmless

Mast cells are prominent in ______ and ______ tissues

• mucosal

• epithelial

*high numbers of mast cells found in mucosal surfaces of the respiratory and GI tract

Mast cells are key for allergic responses!! What kinds?

Response can be local (limited) or systemic (life threatening “anaphylaxis”)

Mucosa (aka “mucous membrane”)

soft tissue that lines that body's canals and organs in digestive, respiratory, and reproductive systems

the mucosa is _______ the body, BUT exposed to the _________ world by what we ingest and breathe

• inside body

• exposed to outside world

"sterile" organs

not exposed to the outside world (eg. heart, pancreases, kidney)

Several microenvironments exist within the ______ in which microorganisms can reside

large intestine

Environment is the (driving/modifying) factor behind allergic diseases

driving

Genes are the (driving/modifying) factors behind allergic diseases

modifying

*genetic factors include non-allergic and allergic disorders (eg. asthma, eczema, rhinitis)

Reason for the allergy epidemic:

changes in the incidence of hypersensitivity diseases are occurring too quickly to be due to genetic changes in the population....thus, it must be due environmental factors changing how the immune system functions

The underlying cause of the allergy epidemic is environmental factors changing how the immune system ________

functions

Eukaryote vs Prokaryote

Prok: Archaea and Bacteria

Euk: Eukary

Eukaryotic or prokaryotic: Contain many membrane-bound organelles

eukaryotic

Eukaryotic or prokaryotic: No nucleus

prokaryotic

Eukaryotic or prokaryotic: Larger and more complex

eukaryotic

For gram-staining, (purple/pink) bacteria are gram positive and (purple/pink) bacteria are gram negative

purple; pink

Gram positive

cell membrane has cell wall composed of repeating units (peptidoglycans)

Gram negative

thinner outside; just outer membrane (Lipopolysaccharides)

Gram (negative/positive) bacteria stimulate the immune system

negative

Fungi

Eukaryotic microbes

Fungi Examples

• yeast (unicellular)

• mold (multicellular)

The majority of people infected by at least one parasitic organism are in _____ and _______ regions

tropic; sub-tropic

Protozoa and helminths are examples of _______ organisms

parasitic

Parasites usually require ____ to complete their life cycle

require 2 hosts (eg. malaria)

Leeuwenhoek

• built the first microscope

• first to observe single-celled microbes

Florence Nightingale

• founded the science of medical statistics and devised the “polar area chart” to show deaths of soldiers due to various causes

John Snow

• Birth of Epidemiology

• London Cholera Outbreak of 1854 (Broad Street Pump)

• However, his work was prior to the development and acceptance of the “germ theory” and the principles of his work were largely ignored until decades later

Louis Pasteur

• discovered the microbial basis of fermentation

• disproved that microbes arise by spontaneous generation

• developed the pasteurization (the process of heating a liquid to below the boiling point to destroy microorganisms but retain flavors of the liquid)

The Scientific Method: Approach

• Based on direct observations and other information, formulate a "best guess" as to why something occurs

• Set up an experiment to test whether your "best guess" (hypothesis) is true and repeatable

• Include controls (negative and positive)

• Untested hypothesis = opinion

• Hypothesis tested once = anecdote = opinion

Only ______ _______ can determine causation

controlled testing

**Even if an association between two events is observed in 100% of the cases being observed, it doesn't necessarily mean that one event causes the other b/c there could be another causative step common to both events

Association does NOT EQUAL

causation

Mary Catherine Evans

showed that drinking unpasteurized milk could transmit the bacterium that cause brucellosis from farm animals to humans

Ignaz Semmelweis

• ordered doctors to wash their hands with chlorinated lime (antiseptic) as a preventative measure for puerperal fever

• pre-germ theory

Joseph Lister

developed carbolic acid to treat wounds and clean surgical instruments

Aseptic environment

microbe-free

Disinfectant

strong chemical agent that inhibits or kills microorganisms

Antiseptics

Disinfecting agents with low enough toxicity for host cells (can use directly on skin/wounds)

Sterilants

kill both vegetative bacterial cells/spores (when applied for appropriate times and temperatures)

Robert Koch

• discovered that using solid media provided a simple way to obtain pure cultures

• Observed that masses of cells (called colonies) have different shapes, colors, and sizes

• Began with potato slices, but eventually devised uniform and reproducible solidified nutrient solutions

Streak plating

method to obtain pure cultures

1 live microbial cell => 1 colony => 1 CFU (colony forming unit)

• **CFU refers to a single cell that is capable of developing into a visible colony. 

Koch's Postulates

criteria for establishing causative link between infectious agent and disease

Koch's postulates were crucial to…

establish that microbes could cause disease

Pathogen

disease-causing microorganism

Koch’s Postulates

1) Pathogen is always present in diseased host and absent in healthy individuals

2) Pathogen is grown in pure culture - no other microbes present

3) Individual becomes sick when the pure pathogen is introduced into healthy host

4) Same pathogen is re-isolated from now-sick individual

What did Iwanowski's tobacco plant experiment show?

viruses are different from bacteria, scientist who showed that extracts from diseased tobacco plants could transmit disease to other plants after passage through ceramic filters fine enough to retain the smallest known bacteria

What did Beijerinck show about the tobacco mosaic virus?

It was not diluted by filtration and passage through new plants (implied that it was replicating and not a bacterial toxin)

Filtration

• sterilize using filters too small for microscopic cells to pass through

• avoids heating sensitive liquids

Viruses

• metabolically inert sub-cellular agent that can infect specific types of living cells and replicate while inside the cell

• obligate intracellular parasite

• does NOT exhibit “free-living” or “independent” Growth

True or False: Viruses may or may not encode additional genes beyond that necessary for replication and transmission

True

Microbial cells exhibit _____ growth

"free-living" or "independent" growth

Virion Structure

nucleocapsid - capsid (protein coat) and nucleic acid

The two main categories of virions are:

• naked

• enveloped (surrounded by lipid envelope)

Viruses are generally (larger/smaller) than bacteria

smaller

The capsid of a virion is made of repeating subunits called _______

capsomeres

Viruses are typically (symmetric/asymmetric)

symmetric

virus assembly can be…

spontaneous

Enveloped viruses

• Have membrane surrounding nucleocapsid

• Lipid bilayer with embedded proteins

• Envelope makes initial contact with host cell,

• Much of the membrane is picked up from the host cell during exit

Most enveloped viruses infect…

most infect animal cells

Viruses (do/do not) carry out their own metabolism

do not b/c they a metabolically inert

Lysozyme-like enzymes

aid viruses in cleaving virus from host cell during release (eg.influenza’s NA)

RNA replicases

• enzymes that copy RNA from RNA

• needed by RNA viruses

Retroviruses carry which enzyme?

reverse transcriptase

Reverse transcriptase

makes a DNA copy from an RNA template, which violates the central dogma

Viral life cycle

1) Attachment to a susceptible cell: (adsorption) of the virus to a susceptible host cell

2) Entry: (penetration) of the virion or its nucleic acid

3) Synthesis: of virus nucleic acid and protein by cell metabolism as redirected by virus

4) Assembly: of capsids and packaging of viral genomes into new virions (maturation)

5) Release: of mature virions from host cell

There are _____, ______, and ______ passive barriers to infection

physical, chemical, anatomical

Passive barrier: Lysozyme (where + function)

in tears and other secretions; dissolves cell walls

Passive barrier: Removal of particles (what does it)

cilia in nasopharynx

Passive barrier: Mucus and cilia lining trachea (function)

suspend and move microorganisms out of the body

Passive barrier: Skin (type of barrier + function)

physical barrier; produces antimicrobial FAs and anti-bacterial peptides

Passive barrier: stomach acidity (pH 2) (function)

inhibits microbial growth

Passive barrier: Mucus, antibacterial peptides, phagocytes, surfactant (where and function)

lungs; prevents infection

Passive barrier: blood and lymph proteins (function)

inhibit microbial growth