1 / 55

Microbe-Human Interactions

Microbe-Human Interactions. A Continuum of Interactions Exists. Routine Contact with Microorganisms Infection – a condition in which pathogenic microbes penetrate host defenses, enter tissues and multiply Disease – Deviation from Normal Health.

aristotle-mcpherson
Download Presentation

Microbe-Human Interactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Microbe-Human Interactions

  2. A Continuum of Interactions Exists • Routine Contact with Microorganisms • Infection – a condition in which pathogenic microbes penetrate host defenses, enter tissues and multiply • Disease – Deviation from Normal Health

  3. The Normal State is that Humans are Host to a Variety of Microorganisms

  4. Humans are Colonized from the Moment of Birth Babies Readily Acquire Flora During Delivery and from the External Environment

  5. Regions that Host Flora • Skin • Oral cavity • Lower GI tract • Upper Respiratory • Genitourinary Tract

  6. Skin Flora Staphylococcus, Micrococcus Propionibacterium

  7. Flora of the Mouth and Pharynx Streptococcus, Neisseria, Staphylococcus, Lactobacillus, Bacteroides

  8. Colonized Regions of the Respiratory Tract

  9. Flora of the GI Tract Bacterioides, Lactobacillus, Enterococcus, Coliforms

  10. Distribution of Flora

  11. Flora of the Genitourinary Tract Lactobacillus, Streptococcus, E. coli, Staphylococcus

  12. Maintenance of the Normal Resident Flora • Normal flora is essential to the health of humans • Flora create an environment that may prevent infections and can enhance host defenses • Antibiotics, dietary changes, and disease may alter flora • Probiotics – introducing known microbes back into the body

  13. The Process of Disease

  14. Types of Pathogens True vs. Opportunistic Pathogens

  15. True Pathogens • Capable of causing disease in a healthy person • Generally associated with a recognizable disease • Can be weak to fatal in their effects

  16. Opportunistic Pathogens • Cause disease in weakened host • Sometimes cause disease when they colonize a different region of the body • See Table 13.4 for pre-disposing conditions

  17. Pathogenicity vs. Virulence • Pathogenicity = ability to cause disease • Virulence = relative capacity of a pathogen to invade and harm host cells

  18. Gaining Access – Portal of Entry The Skin or Membrane Barrier through which Pathogens Gain Entry to the Body

  19. Pathogens May be Exogenous or Endogenous

  20. Some Agents that Enter the Skin • Staphylococcus aureus • Streptococcus pyogenes • Clostridium sp. • Insect-borne diseases • Hypodermic needle contaminants

  21. GI Tract Entrants • Salmonella sp. • Vibrio sp. • E. coli • Shigella sp. • Entamoeba sp. • Giardia sp.

  22. Respiratory Entrants • This is the most frequent route of entry • Streptococcus (Strep throat) • Influenza viruses • C. diptheriae • B. pertussis • Many others

  23. Urogenital Entry Agents • Syphilis • Gonorrhea • Human Papilloma Virus • HIV • Chlamydia • Hepatitis B

  24. Placental & Neonatal Agents STORCH = Syphilis, toxoplasmosis, others (hepatitis), rubella, cytomegalovirus, herpes simplex

  25. Infectious Dose Minimum number of organisms required for an infection to be successful; lack of ID will not result in infection

  26. To be Successful, a Pathogen Must • Adhere to the host • Penetrate host barriers • Establish a colony in host tissue

  27. Some Methods of Adhesion • Fimbriae • Flagella • Adhesive Capsules • Binding to Receptors (Viruses)

  28. Virulence factors Traits used by pathogens to invade and establish themselves in the host; also determine the degree of tissue damage that occurs

  29. Some Virulence Factors • Extracellular Enzymes • Exotoxins • Endotoxins • Anti-phagocytic Factors

  30. Exotoxins – Secreted by Living Cells Examples: Botulin Toxin, Hemolysins (Strep and Staph)

  31. Endotoxins are Released by Dead Cells Example: Lipopolysaccharides from Gram- cells

  32. Antiphagocytic Factors Ex.: Leukocidins, Slime Layers

  33. The Process of Infection and Disease • Distinct stages of clinical infections: • incubation period - time from initial contact with the infectious agent to the appearance of first symptoms; agent is multiplying but damage is insufficient to cause symptoms; several hours to several years • prodromal stage – vague feelings of discomfort; nonspecific complaints • period of invasion – multiplies at high levels, becomes well established; more specific signs and symptoms • convalescent period – as person begins to respond to the infection, symptoms decline

  34. Patterns of Infection • Localized - Contained • Systemic – Agent Circulates Freely • Focal – Localized infection breaks loose or attacks a distant target with toxin • Mixed – more than one agent invades

  35. Temporal Patterns of Infection • Acute = short-lived but severe • Chronic = long-lived, persistent

  36. Signs of Disease vs Symptoms • Signs = objective evidence of disease • Symptoms = subjective evidence sensed by patient (discomfort)

  37. Some Signs of Infection • Inflammation • Skin lesions • Elevated WBC count • Bacteria or virus in blood

  38. Portals of Exit for Pathogens • Respiratory/ Salivary • Skin • GI tract • Urogenital • Blood

  39. Persistence of Infection • Latent infections & recurrent disease • Sequelae – long term damage to organs/tissues

  40. Epidemiology The Study of Disease in Populations

  41. Classifications of Diseases • Endemic – exhibits a relatively stable frequency in a particular location over time • Sporadic – occasional cases at irregular intervals • Epidemic – increase beyond what might be expected in a given population • Pandemic – spread of epidemics across continents

  42. Patterns of Diseases

  43. Pathogen Reservoirs vs Sources • Reservoir = habitat where the organism occurs • Source = Actual contact which provides the infection

  44. Disease Carriers Shelter and Spread a Pathogen Inconspicuously

  45. Carrier States • Asymptomatic – No signs of infection • Incubation – Spreads infection while it is incubating (still no symptoms) • Convalescent – Sheds microbes while recuperating • Chronic – Latent infections can be sheltered after apparent recovery • Passive – Mechanically picks up and transfers microbes

  46. Disease Vectors Animals that transport an infection from one host to another

  47. Biological Vectors • Actively participate in pathogen’s life cycle • Can inject infected saliva (mosquito) • May defecate around bite wound (flea) • Regurgitate blood into a wound (tsetse fly)

  48. Mechanical Vectors Move the Pathogen from one Host to Another Without being Infected

  49. Zoonosis An infection naturally found in animals, but transmissible to humans (See Table 13.10)

  50. Communicable & Contagious Diseases • Communicable diseases can be transferred from one host to another and infection established • Contagious diseases are highly transmissible and move readily from host to host • Non-communicable diseases are not transmitted from one host to another

More Related