PATHOGENS

Question 1

Pathogens

Answer 1

Pathogens are anything that can cause a disease or trigger an immune response (inflammatory reaction).

Question 2

Inflammation

Answer 2

Inflammation – a biological response to harmful stimuli. Includes:

1. A vascular response – vasodilatation and permeability to allow fluids migrate into the tissue.
2. Cellular response – 𝑅𝐵𝐶 come to the site of the pathogen and fight it.

Question 3

Sings of inflammation in a tissue:

Answer 3

1. Redness – due to vasodilatation (the presence of more 𝑅𝐵𝐶 causes the site to be redder).
2. Heat – due to vasodilatation (the presence of more 𝑅𝐵𝐶 increases the heat in the area).
3. Swelling – due to vasodilatation permeability more fluids can pass and accumulate.
4. Pain.
5. Loss of function (of the cell tissue)

Question 4

Types of organism pathogens:

Answer 4

1. Bacteria.
2. Viruses.
3. Fungi.
4. Parasites

Question 5

Bacteria

Answer 5

Unicellular prokaryotic organism found in every habitat on Earth. They can be both harmful and beneficial.

Question 6

Bacteria structure

Answer 6

• bacteria do not have membrane bond organelles.
• bacteria have circular 𝐷𝑁𝐴 in a nucleoid region.
• Some bacteria may have plasmids (small circular 𝐷𝑁𝐴 segments in their cytoplasm).
• Some bacteria may have additional structures:
  - Flagella – helps in movements.
  - Fimbriae – helps in movements and tearing or
  sticking to tissues.
  - Pili – allows plasmid exchange.
• bacteria have cell wall; it is composed of:
  - Phospholipid bilayer.
  - Peptidoglycan layer.
• Some bacteria may have capsule – allows bacteria to stick to tissues.
• Some bacteria may form endospores – method that let bacteria be durable and survive in any place under any conditions. This happens by the stopping of all the bacteria’s metabolic processes.

Question 7

Bacterial Replication

Answer 7

Bacteria are reproduced by binary fission. It is a form of asexual reproduction producing two identical
clone-daughter cells. In this process there is no genetic variability (therefore, no incensement in genetic
variability).

Question 8

Bacteria can increase genetic variability by:

Answer 8

• Conjugation (bacterial mating) – transfer of plasmids between bacteria through pili.
• Transformation – incorporation of 𝐷𝑁𝐴 from the environment.
• Transduction – a transfer of 𝐷𝑁𝐴 between bacteria by viruses called bacteriophages.

Question 9

Classification of bacteria:

Answer 9

1. Shape of the bacteria.

2.Gram stain – a technique used to differentiate bacteria base on the structural difference in their
cell wall (presence of peptidoglycan).

Question 10

Classification of bacteria by Shape

Answer 10

• Cocci – circle shaped.
• Rods/bacilli – rod shaped.
• Spirilla – spiral shaped

Question 11

Classification of bacteria by Gram

Answer 11

• Gram positive (𝐺 +) pained blue – has two layers in the cell wall:
• Phospholipid bilayer.
• Think peptidoglycan layer.
• Gram negative (𝐺 −) painted red – has three layers in the cell wall:
• Phospholipid bilayer.
• Thin peptidoglycan layer.
• Lipopolysaccharide.

Question 12

Gram Positive

Answer 12

Gram positive bacteria have a thick layer of peptidoglycan in their cell wall. Peptidoglycan absorbs the crystal violet staining, making it appear blue under the microscope. Gram positive are more receptive to
antibiotics then gram negative, due to their expose peptidoglycan layer (gram negative have more
membrane layer).

Question 13

Examples of Gram Positive

Answer 13

• Streptococcus (𝐺 + 𝐶𝑜𝑐𝑐𝑖 ) – can cause tonsillitis and meningitis that can lead to:
  - Endocarditis – valve inflammation.
  - Glomerulonephritis – kidney inflammation.
• Staphylococcus (𝐺 + 𝐶𝑜𝑐𝑐𝑖 ) – can cause folliculitis and osteomyelitis that can lead to:
  - Toxic sock syndrome (𝑇𝑆𝑆) – characterized by
  fever, muscle aches and low blood pressure.
  - Methicillin resistant staphylococcus aureus (𝑀𝑅𝑆𝐴)
  –> hospital germ (resistant to most antibiotics)

Question 14

Gram Negative

Answer 14

Gram negative bacteria have a cell wall with thin layer of peptidoglycan covered by additional outer
membrane. Peptidoglycan layer is sandwiched between two membranes and can’t absorb the crystal violet stain, thus painted red under the microscope.

Question 15

Examples of Gram negative

Answer 15

• Salmonella – causes severe food poisoning, and can come from raw eggs or chickens.
• Escherichia coli (𝐺 − 𝑅𝑜𝑑) – commonly found in the lower intestine and are usually harmless.
  Pathogenic stains can cause serious food poisoning, gastro enteritis(𝐺𝐸) and urinary truck infection (𝑈𝑇𝐼).
• Yersinia pastis (𝐺 − 𝑐𝑜𝑐𝑐𝑖𝑏𝑎𝑠𝑖𝑙𝑖) – caused the black plague.

Question 16

Viruses

Answer 16

Infectious agents that are obligate parasites that can only reproduce inside other living cells.
Structure:
1. Capsid protein coat.
2. Genetic material (𝐷𝑁𝐴 or 𝑅𝑁𝐴).

Question 17

Replication of Viruses

Answer 17

1. Attachment to the ells membrane.
2. Penetration by endocytosis.
3. Uncoating.
4. Incorporation of 𝐷𝑁𝐴 into the cell’s genome. Reverse transcriptase (𝑅𝑇) changes 𝑅𝑁𝐴 to 𝐷𝑁𝐴, in
   case the virus has 𝑅𝑁𝐴.
5. Replication of all viral components.
6. Assembly.
7. Release and destruction of the cell.

**Stages 1-4 are called the latent phase, while stages 3-7 are called lytic phase

Question 18

Classification of Viruses

Answer 18

• 𝐷𝑁𝐴 virus.
• 𝑅𝑁𝐴 virus.
  Both can contain either double or single stranded nucleic acid.

Question 19

Examples of 𝑹𝑵A

Answer 19

• Influenza
• Rhinovirus – causing flue
• Human immunodeficiency (𝐻𝐼𝑉) – causing to
  acquired immune deficiency syndrome.

Question 20

Examples of DNA

Answer 20

-Herpes simplex virus (𝐻𝑆𝑉) – replicates in nerve
cells and causes in genitals and in the lips.

• Human papilloma virus (𝐻𝑃𝑉) – replicates in
  epithelium tissues. Increases chances for cervical
  cancer.
• Epshtein Barr virus (𝐸𝐵𝑉) – causing mononucleosis
  (kissing disease).
• Hepatitis B. virus – causing inflammation in the
  liver

Question 21

Fungi

Answer 21

Unicellular eukaryotic organism that compose a non-motile multicellular body called mycelium (fungi

mattress. ) Come in the shape of:
* Molds (columnar cells).
* Yeasts (dots).

**Candida – yeast fungi that causes candidiasis (inflammation caused by the fungi).

Question 22

Parasites

Answer 22

Eukaryotic organism that lives in or on a host organism and benefits at the expense.
Types:
* Unicellular (protozoa).
* Multicellular (helminth).

Question 23

Protozoa examples:

Answer 23

• Plasmodium – transmitted by mosquito bites and cause malaria (destroys 𝑅𝐵𝐶, causes fever and
  sever cases of death).
• Leishmania – transmitted by sand-fly bites and causes leishmaniosis (body ulcers).

Question 24

Helminths examples:

Answer 24

• Enterobirous (pinworm) – transmitted by ingestion or anal insertion and causes peri-anal itch (common in children).
• Tenia solium (pork tapeworm) – transmitted by ingestion uncooked pork and causes cysticercosis cyst in the brain and muscles.