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  2. 2. <ul><li>1. Saprophytes. </li></ul><ul><ul><ul><li>Free living in water, soil. </li></ul></ul></ul><ul><ul><ul><li>No multiplication. </li></ul></ul></ul><ul><ul><ul><li>No infectious disease </li></ul></ul></ul><ul><ul><ul><li>Except B. subtilis. </li></ul></ul></ul><ul><li>2.Pathogens: </li></ul><ul><li>3. Commensals </li></ul><ul><ul><ul><li>Opportunistic pathogens </li></ul></ul></ul>2 Classification of microbes
  3. 3. 2 Definition Invasion (entry,fixation) and multiplication of microbes in body tissues, which may be clinically unapparent or result in local cellular injury due to competitive metabolism, toxins, intracellular replication or antigen antibody response. All infections not results in Infectious disease.
  4. 4. Classification of infections 1.Based on Occurrence: a).Primary infection: Infection is first time with a microbe. b).Reinfection: Subsequent infections with same microbe. c).Secondary infection: Infection followed by lowered Host immunity by preexisting disease. 4
  5. 5. d). Focal infection: Localized infection with generalized symptoms. Ex: Appendicitis, Tonsillitis e).Cross infection: New infection in a patient from another host or source. f).Nosocomial infection: If cross infections occur in hospitalized individual (Hospital acquired infection). 5
  6. 6. g). Iatrogenic infection: Infections by means of Investigative & therapeutic procedures. 6
  7. 7. <ul><li>Based on source </li></ul><ul><li>Endogenous: </li></ul><ul><ul><ul><li>From Normal flora. </li></ul></ul></ul><ul><li>Exogenous: </li></ul><ul><ul><ul><li>Another individual. </li></ul></ul></ul><ul><ul><ul><li>Environment . </li></ul></ul></ul><ul><li>Based on clinical effects: </li></ul><ul><li>Inapparent (Sub clinical): </li></ul><ul><li>No S/S in spite of </li></ul><ul><li>infection. </li></ul><ul><li>Atypical infection: </li></ul><ul><li>Absence of typical </li></ul><ul><li>manifestations. </li></ul><ul><li>Latent infection : </li></ul><ul><li>Followed by infection- </li></ul><ul><li>Microbe retain in tissues. </li></ul><ul><li>Starts proliferation with </li></ul><ul><li>lowered immunity. </li></ul>7
  8. 8. <ul><li>1.HUMAN BEINGS </li></ul><ul><li>Commonest source. </li></ul><ul><li>Infective agent </li></ul><ul><li>transferred either from </li></ul><ul><li>Patient or from </li></ul><ul><li>Carrier. </li></ul>SOURCES OF INFECTION Types of carrier: Depending on origin: A. Healthy carrier B. Convalescent carrier C. Contact carrier: Acquires pathogen from patient. D. Paradoxical carrier. Acquires pathogen from another Carrier . 8
  9. 9. <ul><li>Based on the duration of carriage …… </li></ul><ul><li>A. Temporary carrier: </li></ul><ul><li>Microbes harbors not </li></ul><ul><li>more than 6 months. </li></ul><ul><li>B. Chronic carrier: </li></ul><ul><li>Microbes harbors </li></ul><ul><li>several years or even </li></ul><ul><li>for life. </li></ul>2. INSECTS VECTOR. a). Mechanical vectors. b). Biological vectors. 9 “ Arthropod borne diseases ”
  10. 10. 3).ANIMALS: Infectious diseases transmitted from animals to man. ZOONOSES. a).Bacterial: Leptospira, plague from Rat. b).Viral : Rabies from dog. c).Protozoa: Leishmaniasis from dog. d).Helminths : Hydatid disease from dog Tape worms : Cattle , Pig. e).Fungal: Zoophilic dermatophytes - Dog. 10
  11. 11. <ul><li>SOIL & WATER </li></ul><ul><li> Soil : Spores of Tetanus bacilli </li></ul><ul><li> Histoplasma and Nocardia spp. </li></ul><ul><li>Water: Cholera, H A V , H E V, </li></ul><ul><li> Typhoid etc. </li></ul><ul><li>FOOD </li></ul><ul><li> Contaminated food. </li></ul><ul><li> Ex: Staphylococci, Cl. Botulinum. </li></ul>11
  12. 12. 1.Contact: i) Direct ex: STDs. ii) Indirect : Through contaminated fomites like Toys, Pencils, Clothing. Ex: Diphtheria, Trachoma. METHODS OF TRANSMISSION 12
  13. 13. <ul><li>Inhalation </li></ul><ul><li>Secretions from Respiratory tract infections. </li></ul><ul><li>(Sneezing, Speaking, Coughing) </li></ul><ul><li> DROPLET NUCLEI </li></ul><ul><li> & AEROSOLS </li></ul><ul><li>Ex: H. influenza, </li></ul><ul><li> Tubercle bacilli. </li></ul>13
  14. 14. <ul><li>Ingestion: </li></ul><ul><li>Through food & water. </li></ul><ul><li>Ex: Cholera, Dysentery, </li></ul><ul><li> Food poisoning with </li></ul><ul><li>B. cereus, Staphylococci. </li></ul><ul><li>Inoculation: </li></ul><ul><li>Pathogen injected into tissues. </li></ul><ul><li> Ex:Tetanus spores. </li></ul><ul><li> Arboviruses (Insects). </li></ul>14
  15. 15. 5. Congenital transmission: (Transplacental , Vertical transmission) Placental defects results in Congenital transformation of microbes and results in malformations. ( Teratogenic infections ). Ex : To R C H complex . 15
  16. 16. <ul><li>7. Iatrogenic infections </li></ul><ul><li>Procedures like…. </li></ul><ul><ul><ul><li>Dialysis, </li></ul></ul></ul><ul><ul><ul><li>Transfusions, </li></ul></ul></ul><ul><ul><ul><li>Heart Surgery, </li></ul></ul></ul><ul><ul><ul><li>Transplant Surgery, </li></ul></ul></ul><ul><ul><ul><li>Injections. </li></ul></ul></ul><ul><ul><ul><li>Lumbar puncture. </li></ul></ul></ul><ul><ul><ul><li>Catheterization . </li></ul></ul></ul>16
  17. 17. <ul><li>DETERMINANTS OF PATHOGENICITY </li></ul><ul><ul><ul><li>Pathogenicity: </li></ul></ul></ul><ul><ul><ul><li>Disease producing capacity of </li></ul></ul></ul><ul><ul><ul><li>species. </li></ul></ul></ul><ul><ul><ul><li>Virulence: </li></ul></ul></ul><ul><ul><ul><li>Disease producing capacity of </li></ul></ul></ul><ul><ul><ul><li>a strain. </li></ul></ul></ul><ul><ul><ul><li>Exaltation: </li></ul></ul></ul><ul><ul><ul><li>Enhancement of pathogenicity. </li></ul></ul></ul><ul><ul><ul><li>Attenuation: </li></ul></ul></ul><ul><ul><ul><li>Retaining antigenicity and </li></ul></ul></ul><ul><ul><ul><li>loss of pathogenicity. </li></ul></ul></ul>17
  18. 18. <ul><li>Adhesion: Adhesions . </li></ul><ul><li>Fimbriae, Pili (Colonization factor) . </li></ul><ul><ul><ul><li>Prevents flushing away process. </li></ul></ul></ul><ul><ul><ul><li>High concentration of toxins. </li></ul></ul></ul><ul><ul><ul><li>Facilitates penetration into host cells. </li></ul></ul></ul><ul><ul><ul><li>All are antigenic in nature. </li></ul></ul></ul>19
  19. 19. <ul><li>Invasiveness: </li></ul><ul><ul><ul><li>Ability of an organism to invade the host cells after establishing the infection. </li></ul></ul></ul><ul><ul><ul><li>Antiphagocytic factors- </li></ul></ul></ul><ul><ul><ul><li>Capsule, Streptococcal ‘M’ protein. </li></ul></ul></ul><ul><ul><ul><li>Cytotoxins: Haemolysins, Leucocidins. </li></ul></ul></ul><ul><ul><ul><li>Bacterial surface antigens. </li></ul></ul></ul><ul><ul><ul><li>Vi antigen ,K antigen. </li></ul></ul></ul><ul><ul><ul><li>Enzymes: Coagulase. </li></ul></ul></ul><ul><ul><ul><li> Hyaluronidase & Collaginase. </li></ul></ul></ul>20
  20. 20. 21 <ul><li>3.Toxigenicity: </li></ul><ul><ul><li>Toxin producing capacity. </li></ul></ul><ul><li>Exotoxins </li></ul><ul><li>Endotoxins </li></ul><ul><li> Superantigens </li></ul>
  21. 21. <ul><li>Exotoxin Endotoxin </li></ul><ul><ul><ul><li>Proteins. - Protein ,Polysaccharide & </li></ul></ul></ul><ul><li> lipid </li></ul><ul><ul><ul><li>Heat labile. - Heat stable. </li></ul></ul></ul><ul><ul><ul><li>Secreted by cells - Part of cell wall. </li></ul></ul></ul><ul><ul><ul><li>Separable from culture. - Only by cell lyses. </li></ul></ul></ul><ul><ul><ul><li>Enzymatic action. - No enzymatic action. </li></ul></ul></ul><ul><li>-Effect is - Non specific . </li></ul>Specific 21
  22. 22. <ul><li>Tissue specific. - Not. </li></ul><ul><li>Active in doses. - doses. </li></ul><ul><li>Highly antigenic. - Weakly…. </li></ul><ul><li>Neutralized by antibody - But not…. </li></ul><ul><li>Can be - Cannot be… </li></ul><ul><li>Produced by Gram positive - Gram negative. </li></ul><ul><li>bacteria bacteria </li></ul><ul><li>Except: Shigella, Cholera, </li></ul><ul><li>E T E C. </li></ul>Minute Large Toxoided 22
  23. 23. <ul><li>Plasmids: </li></ul><ul><li> R - factor </li></ul><ul><li>E. coli. -> Enterotoxin. </li></ul><ul><li> Toxins from Staph. aureus. </li></ul><ul><li>Communicability: </li></ul><ul><li> Ability of a pathogen to into </li></ul><ul><li>community. </li></ul><ul><li> High for Respiratory, Intestinal infections. </li></ul>Spread 23
  24. 24. <ul><li>Infecting dose: </li></ul><ul><ul><ul><li>M I D : Minimum infecting dose. </li></ul></ul></ul><ul><ul><ul><li>M L D : Minimum lethal dose. </li></ul></ul></ul><ul><li>Bacteriophages: </li></ul><ul><ul><ul><li>Viral particles infecting bacteria. </li></ul></ul></ul><ul><li>Ex: Diphtheria toxin. </li></ul><ul><li>9. Route of infection: </li></ul><ul><li>Streptococci: Any route. </li></ul><ul><li>Cholera: Oral route only. </li></ul>25
  25. 25. TYPES OF INFECTIOUS DISEASES 1. Depending on location: Superficial a). Localized Deep seated. b). Generalized. Bacteremia : Septicemia : Bacteria + Toxins. Pyemia : Bacteria , Toxins and Multiple abscesses in internal organs. 26
  26. 26. 2. Depending on Spread : A. Endemic : Constantly present in a particular area. Ex: Typhoid, Malaria. B. Epidemic : Rapid spread with involving many persons. Ex: Influenza. 27
  27. 27. <ul><li>Pandemic: </li></ul><ul><li>Epidemic , that spreads many parts of </li></ul><ul><li>the world within a short time. </li></ul><ul><li>Ex : Influenza, Cholera, </li></ul><ul><li>Plague, Viral conjunctivitis. </li></ul><ul><li>4. Prosodemic: </li></ul><ul><li>Slowly spreading epidemic. </li></ul><ul><li>Ex : Cerebrospinal fever. </li></ul>28