MICROBES

• Microbe


  Organism that cannot be seen with the naked eye, exists as single cells or cell clusters, and can be appreciated with the aid of a microscope
• Groups of microorganisms


  • Bacteria
  • Fungi
  • Viruses
  • Protozooans
• Microbes play very important roles in nature than their small size suggest
• Microbes form a significant integral part of the community that ensure interaction between living and non-living components and hence the sustenance of all ecosystems
• Microbes ensure the synthesis and degradation of special organic substances in the course of their existence
• Ways man has taken advantage of microbes

  • Production of beer, yogurt and antibiotics
  • Baking
  • Soak away system
• Human microflora


  Microbes that occur on the skin, orifices, body fluids, and tissues, most of which form normal body microflora and are not harmful to the host
• Pathogenic microbes


  Microbes that elicit disease conditions in the host, resulting in the loss of productivity
• How microbes elicit disease condition

  1. Establish contact

  2. Multiply

  3. Colonize host superficially or in tissue

  4. Conquer host's defense mechanisms
• Microbes


  • They show preferences for site of occurrence
  • e.g. Neisseria gonorrhoeae sticks strongly to the inner lining of the urogenital tract
• Activities of pathogenic microbes

  • Production of excretory wastes (toxins)
  • Depriving host of nutrients
  • Confiscating host tissue for personal use
  • Destroying host tissue
  • Initiating tissue changes leading to cancers or tumors
  • Reducing host immune response
• Reservoirs


  Natural environments where microbes reside temporarily, including water, soil, atmosphere, humans, domestic and wild animals
• Diseases that are contractible by humans from other animals are termed zoonotic diseases
• Ways microbes transmit


  1. Contaminated food and water (oral-fecal route)

  2. Contamination of the respiratory tract (respiratory route)

  3. Direct contact with infected persons, animals or contaminated objects

  4. Inoculation through the skin
• Types of microbial diseases

  • Bacterial diseases
  • Fungal diseases
  • Viral diseases
  • Protozoan diseases
• Viruses


  The smallest organisms described, obligate parasites that show evidence of living only when in their host, cannot be seen under a common light microscope, occur, live and multiply within the cell of their host, and take over the control of such cells from their respective nuclei and from the host
• Several human diseases are caused by bacteria of various types
• Bacteria are among the smallest living organisms
• Bacteria are the first group of micro-organisms to be discovered as a disease causing organism
• Bacteria


  Most of them gain entry into their host via the mouth, nose, vagina, anus or lacerated skin
• Bacteria


  They obtain their food from their host by secreting enzymes that break down food substances to simpler forms that are readily absorbed by them
• Bacteria


  They also secrete waste products that are usually toxic to their host
• Types of diseases


  • Viral diseases
  • Bacterial diseases
  • Fungal diseases
  • Protozoan diseases
• Viruses


  They are the smallest organism described, i.e. virus
• Viruses


  They can not be seen under the common light microscope
• Viruses


  They are obligate parasites that show evidence of living only when in their host
• Viruses


  Outside their host they are inert; hence they me regarded as organisms at the borderline between living and non-living things
• Viruses


  They usually occur, live and multiply within the cell of its host and they take over the control of such cells from their respective nuclei and from the host
• Viruses


  One of the general characteristics of viruses is their ability to alter the working method or system of the cells of a host
• Viral diseases covered


  • Polio
  • Yellow fever
  • Measles
  • Smallpox
  • Common cold (catarrh)
  • AIDS
• Viral diseases are usually difficult to treat owing to the fact that they reside within the host's cell where drugs cannot be tolerated
• An effective drug at this point may kill the host cell before the virus
• Prevention of viral diseases

  More emphasis is placed on prevention, which ensures that the pathogens do not find their way into the host cell
• When viruses do find their way into the host cell, the microbe is usually left for the host's immune system to handle
• Bacterial diseases covered


  • Cholera
  • Tuberculosis
  • Pneumonia
  • Gonorrhea
  • Syphilis
  • Tetanus
  • Leprosy
• Fungal diseases


  Disease causing fungi in man are few
• Trichophyton sp


  Causes 'ringworm' and 'athletes foot' diseases in children and adults, respectively
• Trichophyton sp


  Obtains its nourishment from the outer layer of the skin with the aid of root-like structures called hyphae
• Ringworm


  Gives a small dark or red patch that grows, but becomes restricted to the outer margin of a portion with restored skin colouration and without hair strands later
• Fungal diseases


  Spread by personal or indirect contact achieved by way of sharing clothing and other personal effects such as sponge, comb, socks etc.