Pathology - the scientific study of the nature of disease and its causes

A PATHOGEN is any disease causing agent. Quick Exercise: How many diseases can you think of?

The A to Z of Germs...”http://thenextweb.com/shareables/2012/06/02/the-a-to-z-of-germs-and-diseases-like-no-childrens-video-youve-seen-before-video/

Ch 20: bacteria and viruses

Other diseases are not contagious:cancer, lupus, arthritis, allergies

This unit will focus on the first type:  the disease, its agents, treatment and history and will cover three main areas of pathology

1.  Viruses  (virology)2.  Bacteria  (bacteriology)3.  Parasites (parasitology)

Some diseases are communicable (can pass to others), such as:

anthrax, swine flu, herpes, common cold, malaria, salmonella, AIDS

Definitions you know

• Host - organism which provides nutrients, etc. to another organism

• Parasite - organism which lives at the expense of (and may even harm) its host; the parasite is generally smaller than the host and is metabolically dependent upon it

• Disease - an upset in the homeostasis of the host, resulting in generation of observable changesEpidemic - when a disease

affects a community

Pandemic - when a disease affects the world

Viruses: Are very small infectious particles consisting of nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope

Viruses are pathogens that attack cells from the inside by hijack the cells own DNA and use it against you.  A virus cannot be treated with antibiotics, it can only run its course until your immune system kicks it out.

..Even then, the virus may lay dormant within the cells and come back at a later date

Adenovirus - cause of the common cold

•Viral genomes may consist of– Double- or single-stranded DNA– Double- or single-stranded RNA

Parts of VirusNucleic acid

-Double- or single-stranded DNA or Double- or single-stranded RNAcapsid

– Is the protein shell that encloses the viral genomeEnvelopes

–Membranous coverings (derived from the membrane of the host cell)

18 250 mm 70–90 nm (diameter)

20 nm 50 nm(b) Adenoviruses

RNADNACapsomere

Glycoprotein

Virus Structure

Properties of viruses•no cellular components - no cytoplasm, ribosomes•they cannot grow•only reproduce inside a host cell•they consist of 2 major parts - a protein coat (capsid), and

hereditary material (DNA or RNA)•they are extremely tiny, much smaller than a cell and only

visible with advanced electron microscopes

Parasitic Nature • Obligate intracellular parasites (they cannot exist

independently)• Specific to hosts (human, dog, some can cross species) • Specific to cells , the common cold is a virus that specifically

attacks cells of the respiratory track (hence the coughing and sneezing and sniffling). HIV specifically attacks white blood cells

This is a bacteriophage, a type of virus that attacks bacteria. It is recognizeable because it looks like the lunar landing spaceship.

See animation http://www.youtube.com/watch?v=41aqxcxsX2w&feature=related

Categories of Viruses

Bacteriophages - infect bacteriaRetroviruses - have RNA instead of DNA

-most viruses are classified by what they infect: animal, plants, etc

Check out this Gallery at Virusworld

More virus images at the end of this presentation!

Viral Reproduction 

Lytic cycle = reproduction occurs, cells burstLysogenic cycle = reproduction does not immediately occur (dormancy) 

Virulent = viruses that undergo both cycles

https://youtube.googleapis.com/v/Rpj0emEGShQ

Steps of virus production (lytic cycle) 1. Attachment- capsid combines with receptor 2. Penetration - the virus is engulfed by the cell (Cell can enter Lysogenic or Lytic Cycle)3. Biosynthesis - viral components are made (protein coat, capsid, DNA/RNA)4. Maturation - assembly of viral components5. Release - viruses leave host cell to infect new cells (often destroys host)

Viruses multiply, or replicate using their own genetic material and the host cell's machinery to create more viruses. Viruses cannot reproduce on their own, and must infect a host cell in order to create more viruses.

(See McGraw Hill animation) http://highered.mcgraw-hill.com/sites/007352543x/student_view0/chapter20/entry_of_virus_into_host_cell.html

1. Attachment- capsid combines with receptor 2. Penetration - the virus is engulfed by the cell (Cell can

enter Lysogenic or Lytic Cycle)

3. Biosynthesis - viral components are made (protein coat, capsid, DNA/RNA)4. Maturation - assembly of viral components5. Release - viruses leave host cell to infect new cells

(often destroys host)

Lytic vs Lysogenic Pathways of viruses

Starring the phage named Lambda

See: http://highered.mcgraw-hill.com/sites/007352543x/student_view0/chapter20/lambda_phage_replication_cycle.html

Integration: viral DNA incorporated into bacterial DNA in lysogenic cycle

Steps in PathogenesisTo cause disease, a pathogen must:•Contact the host - be transmissible•Colonize the host - adhere to and grow or multiply on host surfaces• Infect the host - proliferate in host cells or tissues•Evade the host defense system - by avoiding contact that will damage it•Damage host tissues - by physical (mechanical) or chemical means

[Image: An emergency hospital ward in Kansas during the 1918 flu]

• Ignaz Semmelweis (1850)

• Observed that women in the maternity wards died of childbed fever. He proposed that it was caused by doctors doing autopsies on the deceased women and then carrying the disease causing agent to healthy women who were in labor.

• His solution: Wash your hands before delivering babies!

• *The Germ Theory did not exist at this time

The Germ Theory (around 1860)

•Single most important contribution by the science of microbiology to the general welfare of the world's people

•The theory that microorganisms may be the cause of some or all disease.

•Key to developing the germ theory of disease was a refutation of the concept of spontaneous generation.

•Specific aseptic techniques are employed to avoid microbial contamination

•Method of prevention of spoilage of liquid foodstuffs – Pasteurization

• Jonas Salk • -polio vaccine

https://youtube.googleapis.com/v/U6-FjtpdePA

Human Immunodeficiency Virus (HIV)•Causes the disease AIDS •Retrovirus (RNA inside a protein coat) •Reverse Transcriptase makes DNA from the virus RNA •DNA inserts into host DNA •Proteins are assembled from the DNA code •Viruses assembled from the proteins •Viruses released from the cell

(Link) HIV Animation - how virus infects cellshttps://youtube.googleapis.com/v/RO8MP3wMvqg

See Also: HIV Coloring Assignment

• Emerging Viruses: illnesses not previously known 

• AIDS, West Nile Virus, SARS, Ebola, Bird Flu 

•Could be mutations of known viruses •Could be viruses exposed when new areas were developed •Could have jumped species (avian flu, swine flu)

Related to Viruses 

Viroids - even smaller than viruses, consist of RNA strands that lack a protein coat

Prions - "rogue protein", believed to be the cause of Mad Cow Disease, also may cause Kuru in cannibal tribes

 http://highered.mcgraw-hill.com/sites/007352543x/student_view0/chapter20/how_prions_arise.html

How Do Vaccines Work?

• Once you have gotten a virus, such as chicken pox, your body develops the immunity to that virus.  

• Vaccines are made by growing a weakened or killed form of the virus

• This form of the virus is injected into a person's body, which causes an immune response, and immunity to the virus.

EX: HPV vaccine

Vaccines are all different and specific, but have the same general goal: weaken the virus or bacteria in a way that allows the recipient to develop an immune response without developing any symptoms of infection. 3 ways they are made:Weaken the virusInactivate VirusUse par of the Virus

Developing a vaccine for AIDS is difficult because it is a RETROVIRUS. RNA mutates easily and each individual virus can be slightly different from the others. In fact, different viruses can exist within the same person.

Why so dangerous?- Attacks immune cells: white blood cells called T lymphocytes

https://www.youtube.com/watch?v=B7ITZgag6w0

Human Immunodeficiency Virus (HIV)•Causes the disease AIDS •Retrovirus (RNA inside a protein coat) •Reverse Transcriptase makes DNA from the virus RNA •DNA inserts into host DNA •Proteins are assembled from the DNA code •Viruses assembled from the proteins •Viruses released from the cell

(Link) HIV Animation - how virus infects cellshttps://youtube.googleapis.com/v/RO8MP3wMvqg

See Also: HIV Coloring Assignment

• RV = rotovirus; DTaP = diptheria, tetanus, pertussis (whooping cough);  Hib = haemophilus influenza type B;  PCV = pneumococcal vaccine; IPV = inactivated polio virus;  MMR = measles, mumps, rubella,  

Some parents are opting out of immunizations due to fears about vaccine safety.

In response, government agencies are producing commercials to encourage parents to get their child vaccinated.

Discuss:

1. What are the risks of vaccines? Are they safe?2. Would you have your own child vaccinated?3. Should the government force immunizations?

https://www.youtube.com/watch?v=zuAhkH5uifo

http://discovermagazine.com/2009/jun/06-why-does-vaccine-autism-controversy-live-on

Pro and Cons of vaccines1. Vaccines can save children's lives. 2. The ingredients in vaccines are safe in the

amounts used. 3. Major medical organizations state that vaccines

are safe.: CDC, Food and Drug Administration (FDA), Institute of Medicine (IOM), American Medical Association (AMA), American Academy of Pediatrics (AAP), UNICEF, US Department of Health and Human Services (HHS), World Health Organization (WHO), Public Health Agency of Canada, Canadian Paediatric Society, National Foundation for Infectious Diseases (NFID), and American Academy of Family Physicians (AAFP).

4. Adverse reactions to vaccines are extremely rare.5. Vaccines protect the "herd.” 6. Vaccines save children and their parents time and

money. 7. Vaccines protect future generations. 8. Vaccines eradicated smallpox and have nearly

eradicated other diseases such as polio. 9. Vaccine-preventable diseases have not

disappeared so vaccination is still necessary. 10.Vaccines provide economic benefits for society.

1. Vaccines can cause serious and sometimes fatal side effects.

2. Potentially harmful ingredients. thimerosal, an organic mercury

3. The government should not intervene in personal medical choices.

4. Mandatory vaccines infringe upon constitutionally protected religious freedoms.

5. Vaccines can contain ingredients some people consider immoral or otherwise objectionable. (use part of stem cell line from 1960s)

6. Vaccines are unnatural, and natural immunity is more effective than vaccination.

7. Diseases that vaccines target have essentially disappeared.

8. Most diseases that vaccines target are relatively harmless in many cases, thus making vaccines unnecessary. (chicken pocks, measles)

Various Images of Viruses for Your Viewing Pleasure

INFLUENZA

BACTERIOPHAGE

• H1N1

• SMALLPOX

BACTERIA

Bacteria are classified into two kingdoms: 1. Eubacteria (true bacteria)2. Archaebacteria (Ancient Bacteria).

BACTERIA: are microscopic Prokaryotes.  (“before nucleus”)-Adapted to living in all environments (even some extreme) – they exist EVERYWHERE

Bacteria Structure

4. Nucleoid region contains a circular loop of DNA

5. Plasmids are rings of DNA, used in reproduction

6. Ribosomes in cytoplasm synthesize proteins

2. Flagella is used for movement

3. Pilli (Fimbrae) help bacteria cling to surfaces (cilia)

(Prokaryotes do not have organelles or a membrane bound nucleus!)

1. Outside the plasma membrane of most cells is a rigid cell wall that keeps the cell from bursting or collapsing

Cell Membrane – regulates what comes in and out of the cell

Cell Wall – maintains shape and form

Capsule – found in virulent bacteria, helps evade immune system

Binary fission is the splitting of a parent cell into two daughter cells; it is asexual reproduction in prokaryotes.

II. Reproduction in Prokaryotes

Genetic recombination can occur in 3 ways in bacteria:

1. Conjugation occurs when a bacterium passes DNA to a second bacterium through a tube (sex pilus) that temporarily joins two cells; the plasmid (DNA) is then exchanged

2.Transformation involves bacteria taking up free pieces of DNA secreted by live bacteria or released by dead bacteria.

3. transduction: bacteriophages transfer portions of bacterial DNA from one cell to another. -Plasmids can carry genes for resistance to antibiotics and transfer them between bacteria by any of these processes

Plasmid – an extra bit of DNA, used in sexual reproduction

Plasmids are also used in genetic engineering

Some bacteria form resistant endospores in response to unfavorable environmental conditions.

Antibiotics

• Antibiotics work by blocking vital processes in bacteria, killing the bacteria, or stopping them from multiplying.– Broad or narrow spectrum

• Quinolones: use hydroxyl radicals, which are molecules that destroy the lipids and proteins that make up a cell's membrane and damage cell DNA, halting replication

• Macrolide: protein synthesis inhibitors• Penicillins: work by destroying the structure of a cell

wall

Prokaryotic Nutrition Bacteria differ in their need for, and tolerance of, oxygen (O2).

a. Obligate anaerobes: no O2 are unable to grow in the presence of O2; this includes anaerobic bacteria that cause botulism, gas gangrene, and tetanus.b. Facultative anaerobes: O2 optional are able to grow in either the presence or absence of gaseous O2.c. Aerobic organisms: need O2 (including animals and most prokaryotes) require a constant supply of O2 to carry out cellular respiration.

staphylococcus is a gram-positive, facultative anaerobe

Autotrophic Prokaryotes•a.   Photoautotrophs are photosynthetic and use light energy to assemble the organic molecules they require.•b.   Chemoautotrophs make organic molecules by using energy derived from the oxidation of inorganic compounds in the environment.

–Reduce CO2 by oxidizing ammonia, nitrites and nitrates –(nitrogen fixing bacteria),

Cyanobacteria Photosynthesize in the same manner as plants, with chlorophyll a

– Believed to have first introduced oxygen into primitive atmosphere

– Formerly classified as algae– For symbiotic relationships: like with fungus to form lichens

Other photoautotrophs use photosystem I only and do NOT give off O2

Nitrogen Cycle

Heterotrophic Prokaryotes: a. chemoheterotrophs that take in pre-formed organic nutrients. ( most common free living bacteria) b. aerobic saprotrophs, decompose almost any organic molecule (in presence of oxyge)    Detritivores (saprophytic bacteria) are critical in recycling materials in the ecosystem; they decompose dead organic matter and make it available to photosynthesizers.

Bacteria have an important role to play in breaking down materials in the environment.

Some are harmful and break down material we'd rather keep, like this image of an infection of necrotizing fasciitis (flesh-eating bacteria)

Symbiotic relationship• Commensalism: one benefits• Mutualistic: both benefit• Parasitic: one benefits, other is harmed

Endospore: dormant form of a pathogen that can become active in favorable conditions

Archaea “ancient bacteria” “extreme prok.” (but more closely related to eukaryote)

• Prokaryote with glycerol linked to hydrocarbon lipids– Bacteria: glycerol liked to fatty acids

• methanogens- often in deep sea vents• Halophile- need high salt concentration• Thermoacidophiles- not acidic environments

THERMOACIDOPHILE – extreme archeon which thrives in acidous, sulfur-rich, high temperature environments - the red stuff on the rocks

THE FUTURE BELONGS TO ARCHAE!

Bacteria Shape & Naming

The Gram stain procedure (developed in the late 1880s by Hans Christian Gram) differentiates bacteria.

a. Gram positive bacteria stain purple, whereas Gram negative bacteria stain pink.

b. This difference is dependent on the thick or thin (respectively) peptidoglycan cell wall.

Bacteria Shapes

Cocci – spheres

Bacilli – rods

Spirilla - spirals

Staph – in clusters

Strep – in chains

Streptococcus

Gram Negative

Gram Positive

Identify

Gram Negative, Bacillus

Gram Positive, Bacillus(Anthrax)

Identify

Gram Positive Staphylococcus

Streptococcus

Strains are responsible for strep throat, and flesh eating bacteria

Staphylococcus aureus

Staph means “bunch of grapes” in greek.oxacillin-resistant Staphylococcus aureus

Staph Infection

Bacillus subtilis

• Gram Positive

• *this is an example of a "poor" stain, it looks both pink and purple. 

• Gram staining takes practice

Tetanus

Rigid muscles from tetanus infectionAlso known as “lockjaw”

Clostridium botulism

Gram positive

Causes food poisoning that is sometimes fatal

All forms lead to paralysis that typically starts with the muscles of the face and then spreads towards the limbs.[1] In severe forms, it leads to paralysis of the breathing muscles and causes respiratory failure. In view of this life-threatening complication, all suspected cases of botulism are treated as medical emergencies, and public health officials are usually involved to prevent further cases from the same source.[1]

• A form of botulism is used in BOTOX treatments, as it paralyzes the muscles of the face and effectively smooths wrinkles.

• Results may vary.

Yersinia Pestis

• The black plague, this bacteria was carried on the fleas of rats.  It was responsible for the deaths of thousands of Europeans from the 8th to the 14th century.

Bacillis Anthracis (Anthrax)

Bacillus (unknown strain)

• Mycoplasmas• Causes pneumonia

• Rickettsia rickettsi

• Rocky Mountain Spotted Fever, carried by ticks

E. Coli

Spirilla Bacteria

Salmonella

Name this Bacteria

Answer: Staphylococcus

Plush Germs

Syphilis E. Coli

Gonorrhea

The Plague (Black Death)

Culturing Bacteria

http://youtube.com/v/4sYSyuuLk5g

http://youtube.com/v/Mj9SUJdpJS4