Microbial Flora

Question 1

The Benefits of the Normal Bacterial Flora?

Answer 1

1. The normal flora synthesize and excrete vitamins
2. The normal flora protects us from pathogens (bad bacteria) by competing for attachment sites, or for nutrients.
3. The normal flora may antagonize other bacteria through the production of substances which inhibit or kill non indigenous species. These substances include certain fatty acids, peroxides or bacteriocins, which inhibit or kill other bacteria.
4. The normal flora stimulates the development of certain tissues, i.e., the caecum and certain lymphatic tissues.
5. The normal flora stimulates the production of cross-reactive antibodies. The normal flora behaves as antigens and induce an immunological response, in particular, an antibody-mediated immune (AMI) response

Question 2

How do bacteria invade the human body?

Answer 2

Mucus membranes

skin: hair follicles, sweat gland ducts,

Parenteral route (microbes that gain access to the body when they are deposited directly into the tissues beneath the skin or mucus membranes)

Microbes must attach to host cell to cause infection:

The attachment between microbe and host is through surface molecules called ADHESINS or LIGANDS that bind to specific receptors on host cells.

Question 3

How do bacteria evade host defenses?

Capsules

Answer 3

Capsules: Impair phagocytosis by certain phagocytic leucocytes

Enzymes: Some enzymes can dissolve materials between cells and form or dissolve blood clots, among other functions

Antigenic Variation: Altering surface antigens so microbe cannot be detected by immune system

Question 4

How do Bacterial Pathogens Damage Host Cells?

Answer 4

By using host nutrients
By causing damage to the immediate vicinity of the invasion
By producing toxins that damage sites far from site of invasion
By inducing hypersensitivity reactions (swelling, or allergic reaction symptoms)

Question 5

Production of Toxins?

Answer 5

Poisonous substances that are transported by blood or lymph and can cause serious or fatal effects.

Exotoxin: can be produced at all times

Endotoxin: released when the cell is challenged/under pressure because of medical treatment. (they cause fever, chills etc)

Question 6

Types of vaccines?

Answer 6

Attenuated whole-agent vaccines: use living but attenuated (denatured) microbes.

Toxoids: Inactivated toxins: are vaccines that are directed at the toxins produced by a pathogen

Subunit Vaccines: Use antigenic fragments of a microbe that best stimulates an immune response
Safe because they cannot reproduce in the person and tend to produce fewer adverse effects.
Safest Vx; produces almost no side effects. Used for HEPATITIS B