Pathogens-Chapter 7.1

Pathogens

Any disease causing microorganisms

Bacterias are classified as _____

Prokaryotes - do not have a nucleus

Bacterial cell structure

Common bacterial shapes

Cocci - spherical cells, singly or in pairs

Bacilli - flagella have rod shaped cells

Spirilla - twisted cells

Vibrio - curved rods comma shaped

Bacterial arrangement

• Singly

• In pairs - diplococci

• In chains - streptococci

• In clusters - staphylococci

Bacteria cell wall

made out of peptidoglycan/murein (network of carbohydrates cross-linked with polypeptides)

• maintain cell shape and structure

Gram positive bacteria

large amount of peptidoglycan (thicker)

• retain crystal violet stain during the decolourization process

Gram negative bacteria

less peptidoglycan and have outer membrane that contains lipopolysaccharides

• lose the crystal violet stain and stained by safranin in the final staining process

Gram staining process

1. Crystal violet

2. Put iodine (act as a mordant, trap crystal violet inside the bacterial cell wall)

3. Alcohol wash

4. Application of safranin (counterstain)

Why are gram negative bacteria more dangerous as disease organisms

Their outer membrane is often hidden by a capsule or slimy layer which hides the antigens of the cell and acts as a camouflage. Harder to kill, quick to develop resistance

Role of capsule in bacteria

Cell wall of some bacteria are covered with a capsule of slime layer (thin)

• made of complex carbohydrate

• Role: protection

Flagellum

movement

Virus

• Extremely small

• Non cellular (non-living)

• Infectious agents

Virus consists of

Nucleic acid

• May be RNA or DNA

Capsid

• made of repeating units of capsomere

Membrane envelope

• for certain virus

• Contain viral proteins

Virus structure (HIV)

Obligate intracellular parasites

can only replicate/multiply inside hosts cell

Viruses do not have a _____ instead they have a outer layer called _______

cell wall, viral envelope

What gives the virus its structure?

The capsid consists of repeating units of capsomere

Differences between viruses and bacteria

Airborne

Indirect transmission

When the moisture in exhaled droplets evaporate leaving dried particles of viruses and some bacteria

Suspended in the air by dust particles and inhaled by another uninfected individual

• particles remain viable for greater distances compared to droplet transmission

Vectors

Indirect transmission

Transfer of pathogen by other animal

• insect that is not affected by the disease transfers the pathogen from an infected individual to an uninfected individual

Ingestion

Indirect transmission

• Consumption of contaminated water or food

Droplet

Direct

• Tiny droplets of moisture containing pathogens emitted while talking or sneezing remains suspended in the air in droplets of saliva or mucus and inhaled by an uninfected individual

Indirect

• When individuals sneezes and viruses remain on objects and an uninfected individual touches the object and then their eyes or face

Bodily fluids

Direct: bodily fluids from an infected individual comes into contact with the mucous membrane or bloodstream of an uninfected individual

Indirect: sharing of needles with an person infected with _____

Contact

Indirect contact: touching an object touched by an infected individual

Direct contact: touching an infected individual

Characteristic of inflammatory response

• Swelling

• Redness

• Heat

• Pain

Roles of inflammatory response (RIP)

• Prevent the damage from spreading

• Remove damaged tissues and cell debris

• Initiate tissue repair mechanism

Inflammatory response occurs when

response to tissue injury (accumulation of tissue fluid)

Antigens

any molecules that stimulates the immune response

Non self antigens

antigens that are not recognized by the immune system as belonging to the host body and will stimulate a further immune response either internal non-specific or specific

Self antigens

antigens that are recognized by the immune system as belonging to the host body and will NOT stimulate a further immune response

Pyrogens

any molecules that will cause a fever

Exogenous pyrogens

pyrogens released by pathogens or non self antigens

Endogenous pyrogens

molecules that are released by our own body such as INTERLEUKIN-1

Fever/Pyrexia

Cytokine induced upward displacement of the thermoregulatory set point

• set point of core body temperature set to a higher temperature due to the presence of cytokines

• Response due to the release of pyrogens

How does a fever help the body recover from infections?

Increased core body temperature during a fever:

• Inhibit bacterial growth by creating an unfavourable environment for bacteria, will not work as well at higher temperatures

• Increases metabolic reactions and enzymatic activity of white blood cells

  • increases the rate of tissue repair by increasing enzymatic activity of WBC

• Increases heart rate and blood flow increases the rate of WBC transported to sites of infection

Lymph node contains ______

masses of lymphoid tissue, the cells are criss crossed by a network of fibres

• Bacteria are trapped in the mesh of fibres as the lymph nodes flow through the nodes

• Macrophage destroy them by phagocytosis

When infections occur, the formation of lymphocytes _____ and the lymph nodes become _____ and ______

increases, swollen and sore

Breaking a fever

Resetting a hypothalamic thermoregulatory setpoint downwards initiates heat loss through vasodilation and sweating

Airborne transmission

Moisture in exhaled droplets evaporate leaving dried particles of viruses and some bacteria

Can be inhaled and remain viable for greater distances compared to droplet transmission

What are modes of transmission that are not passed through direct transmission

V.I.A

• Vectors

• Ingestion

• Airborne

Droplets

tiny droplets of moisture containing pathogens emitted during talking breathing and sneezing are breathed in or ingested with food if particles settle on cutlery