AW

microorganisms in relation to human health: chapter 4

The problem of antibiotic resistance

%%superbugs%% = strains of bacteria, viruses, parasites and fungi that are resistant to most of the antibiotics and other medications commonly used to treat the infections they cause.

→ are mutants who after frequent contact with antibiotics for example changed their DNA → become insensitive to the antibiotic → break it down or render it harmless

example: MRSA

The defense mechanisms of our body against microorganisms

immune system

  • %%non-specific defense%% = the body’s first line of defense against diseases. They are not directed against a particular pathogen.

    • %%skin%% = a barrier with the outside world → protects the body in 3 ways of parasat=ic microorganisms

    • The stratum corneum = the outermost layer of the epidermis

    • The sebaceous and sweat glands secrete acidic and antibacterial substances

    • Body’s bacteria compete with foreign bacteria

    • %%mucous membrane%%

    • epidermis of body cavities is much thinner than the other skin but is also in direct contact with the outside world →mucous glands protect it →create a thin layer of mucus to prevent access to the underlying tissue

    • %%white blood cells and cell signaling%%

    • %%Macrophages%% = specialised cells that are involved in the detection, phagocytosis and destruction of bacteria and other harmful organisms

      %%phagocytosis%% = The process by which a phagocyte (a type of white blood cell) surrounds and destroys foreign substances (such as bacteria) and removes dead cells.

      example:

             1. Bacteria penetrate the skin via a wound
         2. Macrophages leave the capillaries to attack the bacteria
   3. Macrophages phagocyte the bacteria and digest them

    • %%Natural killer cells/ NK-cells%% = a special type of white blood cells that produce perforin that open and drain infected body cells

      %%perforin%% = a protein, released by killer cells of the immune system, which destroys targeted cells by creating lesions like pores in their membranes.

    • %%Signaling molecules%% → secreted by infected cells → 2 important functions

      1. attract macrophages and activate NK-cells
      2. warn other cells to create a protein → prevent multiplication of microorganim

  • %%specific defense%% = consists of mechanisms and agents that target specific antigens

    • characteristics

    1. %%The detection of antigens%%

      %%antigen%% = a specific molecule (a protein) found in the cell membrane of all cells of any organism (including in the protein coat of a virus)

      • via antigens → immunesystem can recognise foreign cells and viruses = %%T- and B-lymphocytes%% → recognise antigen
      • cell membrane lymphocytes have receptor molecules →ability to bind to the antigen = key-lock-principle

    2. %%building memory%%

    after an infection → body produces memory lymphocytes → new infection with same microorganism → faster detection → faster reaction of immunesystem → no sickness → immunity gained

    • %%functions of T-cells or T-lymphocytes%%
    • have membrane receptors to recognise infected cells → bind with it → perforate cell → cell dies
    • T-cells keep on multiplying upon contact → some turn into memory T-cells
    • T-cells produce signaling molecules → stimulate B-lymphocyte production
    • %%functions of B-cells or B-lymphocytes%%
    • recognise antigens → produce antibodies → bind with antigen → create antigen antibody complex →macrophages clean it up
    • B-cells keep on multiplying upon contact → some turn into memory B-cells

How to keep or increase your resistance?

  • get enough sleep
  • excercise regularly
  • have a balanced diet
  • avoid smoking, drugs and excessive alcohol consumption
  • be cautious with the use of medicines

Immunisation

  • %%active immunisation → vaccines%%
    • injection of dead or weakened pathogens → encourage the body to make memory cells and antibodies
  • %%passive immunisation → serum therapy%%
    • injection of anitiserum → presence of antibodies → patient doesn’t produce them → no production of memory cells