Mbp

• Symbiosis


  Relationship where unlike microorganisms exist together
• Three types of symbiotic relationship


  • Commensalism
  • Mutualism
  • Parasitism
• Commensalism


  Form of symbiotic relationship in which two species live together and one species benefits from the other without harming or benefiting the other
• Mutualism


  Symbiotic relationship in which two organisms mutually benefit from each other
• Parasitism


  Form of symbiotic relationship where one party or symbiont (i.e parasite) benefits to the detriment of the other (the host)
• Elements of parasitism


  • Parasite
  • Host

  
• Ectoparasites


  Parasites that live outside the host's body

  
• Infestation


  Invasion of the body by ectoparasites
• Endoparasites


  Parasites that live inside the body of the host

  
• Infection


  Invasion of the body by endoparasites
• Facultative parasites


  Parasites that can live independently of the host (i.e. free living)

  
• Obligate parasites


  Parasites that must live inside a host to complete the life cycle

  
• Permanent parasites


  Parasites that remain in a host from early life to maturity

  
• Intermittent parasites


  Parasites that simply visit the host during feeding time

  
• Incidental parasites


  Parasites that occur in an unusual host

  
• Transitory parasites


  Parasites whose larva develops in a host while the adult is free-living

  
• Erratic parasites


  Parasites that are seen in an unusual organ, different from which it ordinarily parasitizes

  
• Definitive hosts


  Harbor the adult stage of the parasite or where the sexual stage or phase of life cycle of parasite occur

  
• Intermediate hosts


  Harbor the larval stage of the parasite or where the asexual stage of the life cycle of the parasite occurs

  
• Reservoir hosts


  Vertebrate hosts that harbor the parasite and may act as additional source of infection in man

  
• Paratenic hosts


  Serve as means of transport for the parasite so that the infective stage of a certain parasite may reach its final host

  
• Sources of exposure to infection or infestation

  • Contaminated soil or water
  • Food containing the parasites infective stage
  • Blood-sucking insect
  • Domestic or wild animal harboring the parasite
  • Another person and his or her clothing, bedding, or the immediate environment he or she has contaminated
  • One's self (auto-infection)

  
• The most common source of exposure to infection is soil contaminated or polluted with human feces
• Modes of transmission


  • Fecal-oral transmission or Ingestion of contaminated food and water
  • Penetration of the skin from the soil or from the contaminated water
  • Bite of blood-sucking insect vectors
  • Inhalation of eggs
  • Transplacental or congenital infection
  • Transmammary (mother's milk) infection
  • Sexual intercourse
• Portals of exit of parasites

  • Anus
  • Urine
  • Sputum
• Pathogenesis


  Dynamics of any disease process
• Traumatic damage


  Mechanism of damage, the manifestations may be due to the direct physical damage caused by the parasite in the organ it parasitizes or at the point of entry of the parasite

  
• Lytic necrosis


  Enzymes and other substances produced by many parasites that are necessary for them to digest food available in the immediate environment may cause harm to the host tissues

  
• Stimulation of host tissue reaction

  Systemic increase in certain types of cells — circulating in the blood may increase
• Toxic and allergic phenomena (immunopathology)


  Proteins or other metabolites produced by the parasites may lead to hypersensitivity or allergic reactions due to stimulation of antibody production
• Opening of pathways for entry of other pathogens into the tissues


  Presence of the parasites and the damage they produce to the tissues may favor the entry and proliferation of other organisms, especially bacteria

  
• General life cycle of the parasites

  • Source of infection
  • Mode of transmission
  • Infective stage – morphologic form that infects humans
  • Pathogenic stage – morphologic form that is responsible for the pathology produced leading to clinical manifestations
  • Diagnostic stage – morphologic form that can be detected through laboratory methods

  
• Classification of parasites


  • Protozoa
  • Helminths

  
• Groups of protozoa


  • Amoebae and flagellates (Phylum Sarcomastigophora)
  • Sporozoa (phylum Apicomplexa)
  • Ciliates (phylum Ciliophora)

  
• Phyla of helminths


  • Nemathelminthes (roundworms)
  • Platyhelminthes (flatworms)

  
• Classes of flatworms


  • Trematoda (flukes)
  • Cestoda (tapeworms)

  
• Stages of microscopic examination

  • Direct wet preparations
  • Concentration technique/methods
  • Use of permanent stains
• Direct wet preparations


  Purpose: To detect the presence of motile protozoan trophozoites; other stages detected include cysts, oocysts, ova and larvae of worms

  
• Direct wet preparations procedure

  1. Place small amount of unfixed stool on a glass slide

  2. Add a drop of 0.85% saline

  3. Mix using a wooden applicator stick

  4. Place a cover slip on the slide

  5. Examine slide using both low-power and high-power objectives of the microscope
• Concentration techniques


  Purpose: To aggregate parasites present into a small volume of the Sample that enables the detection of small numbers of parasites that might not be detected in direct wet preparations, and to remove debris and other contaminants that might interfere with the microscopic examination