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Infection  Infectious process
Genle-Koch’s postulates  <ul><li>The microorganism must be present in every case of the disease and not be isolated from h...
Infection (infectious process) <ul><li>It is a historically formed complex of biologic events and processes that are occur...
Components of infectious process  Organism Conditions  of interaction   Infectious agent
Pathogenicity  <ul><li>It is a genetically conditioned  possibility of microorganisms to cause  infectious process </li></ul>
Categories of pathogenic microorganisms  <ul><li>True pathogens  (primary pathogens) are capable of causing infection and ...
Classification of pathogenic microorganisms  Pathogenic microbes  Obligate intracellular Facultative intracellular  Obliga...
Virulence  <ul><li>It is a quantitative characteristic of degree of microorganism pathogenicity  </li></ul>
Virulence factors  <ul><li>Adhesion  </li></ul><ul><li>Colonization  </li></ul><ul><li>Invasion  </li></ul><ul><li>Penetra...
Pathogenesis  <ul><li>It is a complex of reactions and mechanisms that are characterized interaction between human organis...
A generalized sequence of the stages of infection  <ul><li>1. Transmission from an external source into the portal of entr...
Reservoir of infection  <ul><li>Sick human (syphilis) </li></ul><ul><li>Sick animal (rabies) </li></ul><ul><li>Carriers (s...
<ul><li>The infectious dose (ID)  refers to the minimum number of microbial cell required to initiate infection in the hos...
Sours of infectious agent <ul><li>Exogenous.   When agents is originating from a source outside the body (the environment ...
Mechanisms of transmission <ul><li>Horizontal transmission   is the spread of infectious disease from person to person </l...
Disease transmission <ul><li>Airborne transmission   (influenza, tuberculosis, diphtheria) </li></ul><ul><li>Food and wate...
Portal of entry  <ul><li>Mucous membrane of gastrointestinal tract ( Salmonella typhi, Shigella dysenteria, Hepatitis A vi...
Mechanisms of pathogen adhesion
Adherence of bacteria  Vibrio holerae on the surface of enterocytes  Gonococci on the surface of urinary epithelium
Action of enzymes  Exoenzymes  dissolve extracellular barrier and make possible  penetration of bacteria through or betwee...
Pathogenic enzymes  Dissolves blood clots  Fibrinolysin  Destroys red blood cells and other tissue cells Lecithinase  Brea...
Definition  <ul><li>Bacteremia.  Indicating the presence of bacteria in the blood, usually transient  </li></ul><ul><li>Vi...
Effects of exotoxins and endotoxins
Action of toxins  Exotoxins  diffuse to target cells, which are poisoned and disrupted
Differential characteristics of bacterial exotoxins and endotoxins (1) Stable at 100 0 C for 1 hour Destroyed rapidly at 6...
Differential characteristics of bacterial exotoxins and endotoxins (2) Low  (toxic in high dose) High  (toxic in minute am...
Classification of exotoxins based on mechanism of action Staphylococcus aureus  Cytotoxin that causes the lysis of human e...
Effects of endotoxin  Activation of Hageman factor  Coagulation Alternative pathway of complement (C3a,C5a) Inflammation  ...
Factors of aggressive <ul><li>Capsule.   Prevents phagocyte from adhering to the bacterium </li></ul><ul><li>Cell wall pro...
Infectious disease  <ul><li>It is an extreme extent of infectious process when precise clinical sings occur and  pathologi...
Types of infection  <ul><li>Localized.   Restricted to a confined area in the body </li></ul><ul><li>Systemic.   An infect...
Type of infection caused by one species of microorganisms   <ul><li>Reinfection   occurs when the human was infected by mi...
Types of infection
Typical stages of an infectious disease  <ul><li>The incubation period ,  which is the time between the acquisition of the...
Stages of infectious disease
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Bohomolets Microbiology Lecture #8

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By Ms. Kostiuk from Microbiology department

Published in: Health & Medicine
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Bohomolets Microbiology Lecture #8

  1. 1. Infection Infectious process
  2. 2. Genle-Koch’s postulates <ul><li>The microorganism must be present in every case of the disease and not be isolated from healthy human or from human with other disease </li></ul><ul><li>The microorganisms must be grown in pure culture from the sick host </li></ul><ul><li>The same disease must be reproduced when a pure culture of the microorganism is inoculated into a healthy, susceptible host (animal) </li></ul><ul><li>The microorganism must then be recovered from the experimentally infected host </li></ul>
  3. 3. Infection (infectious process) <ul><li>It is a historically formed complex of biologic events and processes that are occurred in organism when pathogenic microorganism penetrates and reproduces in it </li></ul>
  4. 4. Components of infectious process Organism Conditions of interaction Infectious agent
  5. 5. Pathogenicity <ul><li>It is a genetically conditioned possibility of microorganisms to cause infectious process </li></ul>
  6. 6. Categories of pathogenic microorganisms <ul><li>True pathogens (primary pathogens) are capable of causing infection and disease on healthy person with normal immune defenses </li></ul><ul><li>Opportunistic pathogens cause disease when the host’s immune system is compromised </li></ul>
  7. 7. Classification of pathogenic microorganisms Pathogenic microbes Obligate intracellular Facultative intracellular Obligate extracellular
  8. 8. Virulence <ul><li>It is a quantitative characteristic of degree of microorganism pathogenicity </li></ul>
  9. 9. Virulence factors <ul><li>Adhesion </li></ul><ul><li>Colonization </li></ul><ul><li>Invasion </li></ul><ul><li>Penetration </li></ul><ul><li>Toxigenicity </li></ul><ul><li>Factors of aggressive </li></ul>Virulence factors are properties of disease-causing microorganism, that enhance their pathogenicity and allow them to colonize or to invade human tissue and disrupt normal body functions
  10. 10. Pathogenesis <ul><li>It is a complex of reactions and mechanisms that are characterized interaction between human organism and microorganisms during infectious process </li></ul>
  11. 11. A generalized sequence of the stages of infection <ul><li>1. Transmission from an external source into the portal of entry </li></ul><ul><li>2. Adherence to mucous membranes </li></ul><ul><li>3. Colonization by growth of the bacteria at the site of adherence </li></ul><ul><li>4. Invasion </li></ul><ul><li>5. Forming of primary inflammatory nidus </li></ul><ul><li>6. Spread agents in the organism </li></ul><ul><li>7. Disease symptoms caused by toxin production or invasion </li></ul><ul><li>8. Host responses, both nonspecific and specific </li></ul><ul><li>9. Progression or resolution of the disease </li></ul>
  12. 12. Reservoir of infection <ul><li>Sick human (syphilis) </li></ul><ul><li>Sick animal (rabies) </li></ul><ul><li>Carriers (salmonellosis) </li></ul><ul><li>Soil (fungal disease, actinomycetal disease) </li></ul>It is the primary habitat in the nature world from which a pathogen originates
  13. 13. <ul><li>The infectious dose (ID) refers to the minimum number of microbial cell required to initiate infection in the host. </li></ul>
  14. 14. Sours of infectious agent <ul><li>Exogenous. When agents is originating from a source outside the body (the environment or another person or animal) </li></ul><ul><li>Endogenous . Already existing on or in the body (normal flora or latent infection) </li></ul>
  15. 15. Mechanisms of transmission <ul><li>Horizontal transmission is the spread of infectious disease from person to person </li></ul><ul><li>Vertical transmission is the spread of infectious disease from parent to offspring during pregnancy or delivering </li></ul>
  16. 16. Disease transmission <ul><li>Airborne transmission (influenza, tuberculosis, diphtheria) </li></ul><ul><li>Food and waterborne transmission (botulism, typhoid fever, hepatitis A) </li></ul><ul><li>Vector transmission (yellow fever, lime disease, viral encephalitis) </li></ul><ul><li>Sexually transmitted disease (syphilis, gonorrhea, genital herpes, AIDS) </li></ul><ul><li>Disease transmitted through direct skin contact (leprosy) </li></ul>
  17. 17. Portal of entry <ul><li>Mucous membrane of gastrointestinal tract ( Salmonella typhi, Shigella dysenteria, Hepatitis A virus) </li></ul><ul><li>Mucous membrane of respiratory tract (Neisseria meningitidis, Mycobacterium tuberculosis, Influenza virus) </li></ul><ul><li>Mucous membrane of urinary and genital tract (Neisseria gonorrhoeae, Treponema pallidum) </li></ul><ul><li>Skin (native and hurt) (Leptospira interrogans, Clostridium tetani) </li></ul>The portal of entry is the site at which a microorganism first contacts host susceptible tissue through that microbe can penetrate into the organism
  18. 18. Mechanisms of pathogen adhesion
  19. 19. Adherence of bacteria Vibrio holerae on the surface of enterocytes Gonococci on the surface of urinary epithelium
  20. 20. Action of enzymes Exoenzymes dissolve extracellular barrier and make possible penetration of bacteria through or between cells to underlying tissues Collagenase and hyaluronidase , which degrade collagen and hyaluronic acid, respectively, thereby allowing the bacteria to spread through subcutaneous tissue.
  21. 21. Pathogenic enzymes Dissolves blood clots Fibrinolysin Destroys red blood cells and other tissue cells Lecithinase Breaks down DNA Deoxyribonuclease Breaks down fat Lipase Breaks down hyaluronic acid, a tissue component Hyaluronidase (spreading factor) Breaks down collagen (connective tissue fiber) Collagenase Coagulates plasma; blood clots Coagulase Breaks down lecithin, a lipid component of mammalian cell membrane Phospholipase Function Enzyme
  22. 22. Definition <ul><li>Bacteremia. Indicating the presence of bacteria in the blood, usually transient </li></ul><ul><li>Viremia. Indicating the presence of viruses in the blood . </li></ul><ul><li>Toxemia . Indicating the presence of bacterial toxins in the blood </li></ul><ul><li>Sepsis. Stage of infectious process when agent is not only present in the blood, but can multiply there </li></ul><ul><li>Septicopyemia. When agent is not only multiply in the blood, but and can form purulent nidus in organs and tissues of sick human . </li></ul>
  23. 23. Effects of exotoxins and endotoxins
  24. 24. Action of toxins Exotoxins diffuse to target cells, which are poisoned and disrupted
  25. 25. Differential characteristics of bacterial exotoxins and endotoxins (1) Stable at 100 0 C for 1 hour Destroyed rapidly at 60 0 C Heat stability Bacterial chromosome Bacterial chromosome, plasmid or bacteriophage Location of genes Lipopilysaccharide (LPS) Polypeptide Chemical Released by cell during lysis Secreted from live cell Manner of release Most of gram-negative bacteria A few gram-positive and gram-negative bacteria Source Endotoxin Exotoxin Property
  26. 26. Differential characteristics of bacterial exotoxins and endotoxins (2) Low (toxic in high dose) High (toxic in minute amounts) Toxicity Systemic: fever, inflammation Specific to a cell type Clinical effects Do not convert to toxoid Convert to toxoid that used as vaccines Toxoid formation Low. Poorly antigenic High. Induces high titer antibodies called antitoxins Antigenicity Yes Usually not Fever stimulation Endotoxin Exotoxin Property
  27. 27. Classification of exotoxins based on mechanism of action Staphylococcus aureus Cytotoxin that causes the lysis of human erythrocytes and some other cells. Hemolysin Corynebacte-rium diphtheriae Causes cell death, often by lysis and/or interference with protein synthesis Cytotoxin Vibrio cholerae Inflammation of the gastrointestinal tract; typically causes excessive secretions of fluid and electrolytes from the lining of the gastrointestinal tract Enterotoxin Clostridium botulinum Interference with nerve transmission Neurotoxin Bacterium-producer General site and mode of action Type of toxin
  28. 28. Effects of endotoxin Activation of Hageman factor Coagulation Alternative pathway of complement (C3a,C5a) Inflammation Bradykinin, nitric oxide Hypotension (shock) Interleukin-1 Fever Mediator or mechanism Clinical findings
  29. 29. Factors of aggressive <ul><li>Capsule. Prevents phagocyte from adhering to the bacterium </li></ul><ul><li>Cell wall protein of gram-positive cocci, such as the M protein of Streptococcus pyogenes and protein A of St. aureus. </li></ul>
  30. 30. Infectious disease <ul><li>It is an extreme extent of infectious process when precise clinical sings occur and pathologic changes in an organism are present </li></ul>
  31. 31. Types of infection <ul><li>Localized. Restricted to a confined area in the body </li></ul><ul><li>Systemic. An infection in which the microorganisms spread throughout the body </li></ul><ul><li>Primary. Caused by one type of microorganisms </li></ul><ul><li>Secondary. Caused by a microorganism following a primary infection </li></ul><ul><li>Mixed. An infection caused by two or more microorganisms </li></ul><ul><li>Subclinical. An infection that does not display any symptoms </li></ul><ul><li>Acute. An infection that appears suddenly, has a short course, is relatively severe </li></ul><ul><li>Chronic. An infection that persist over a long period of time with or without symptoms </li></ul>
  32. 32. Type of infection caused by one species of microorganisms <ul><li>Reinfection occurs when the human was infected by microorganism of same species after recovery </li></ul><ul><li>Superinfection occurs when the human was infected by microorganism of same species during infectious process </li></ul><ul><li>Relapce occurs when symptoms of disease are appeared without exogenous infecting </li></ul>Recovered Reinfection Sick Superinfection Relapce Asymptomatic
  33. 33. Types of infection
  34. 34. Typical stages of an infectious disease <ul><li>The incubation period , which is the time between the acquisition of the microorganisms (or toxin) and beginning of symptoms </li></ul><ul><li>The prodromal period , during which nonspecific symptoms such as fever, malaise, and loss of appetite occur </li></ul><ul><li>The specific-illness (clinical) period , during which the overt characteristic signs and symptoms of the particular disease occur </li></ul><ul><li>The recovery period , during which the illness abates and the patient returns to the healthy state </li></ul>
  35. 35. Stages of infectious disease

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