MICRO Chap 4 Part 1 Human and Microbial Interactions


Published on

Published in: Health & Medicine, Technology

MICRO Chap 4 Part 1 Human and Microbial Interactions

  2. 2. I. NORMAL OR INDIGENOUS FLORA <ul><li>NORMAL FLORA (Indigenous flora) </li></ul><ul><ul><li>microorganisms that are frequently found in particular sites of the body in normal healthy individuals </li></ul></ul><ul><li>HOST </li></ul><ul><ul><li>living organism that harbors another living organism </li></ul></ul><ul><li>PATHOGEN </li></ul><ul><ul><li>a microorganism that causes disease. </li></ul></ul>
  3. 3. <ul><li>CATEGORIES OF NORMAL FLORA </li></ul><ul><li>1. Symbionts (Mutualism) </li></ul><ul><li>-- the microbe and the host are of benefit to one another </li></ul><ul><li>-- ex. Normal flora of the large intestine </li></ul><ul><li>2. Commensals (Commensalism) </li></ul><ul><li>--neutral relationship to the host </li></ul><ul><li>-- microbe receives benefit from the host but host receives no harm/benefit from the microbe </li></ul><ul><li>a. Resident Flora </li></ul><ul><ul><ul><ul><li>most of the flora of the body; present invariably or for weeks/months in a particular environment </li></ul></ul></ul></ul>
  4. 4. <ul><ul><li>b. Transient Flora </li></ul></ul><ul><ul><ul><ul><li>Non-pathogenic or potentially pathogenic microorganisms that establishes themselves briefly for colonization or infection without disease </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Ex. Neisseria </li></ul></ul></ul></ul><ul><ul><li>3. Opportunists </li></ul></ul><ul><ul><ul><li>potential pathogens </li></ul></ul></ul><ul><ul><ul><li>lack the ability to invade and cause disease in healthy individuals </li></ul></ul></ul>
  5. 5. CONDITIONS THAT DETERMINE THE NATURE OF THE FLORA <ul><li>1. Local Physiologic and Ecologic conditions </li></ul><ul><li>a. amounts and types of nutrients available </li></ul><ul><li>b. pH </li></ul><ul><li>c. oxidation-reduction potentials </li></ul><ul><li>d. resistance to local antimicrobial substance </li></ul><ul><li>e. temperature </li></ul><ul><li>f. moisture </li></ul><ul><li>2. Various microbial interactions </li></ul><ul><li>a. competition for nutrients </li></ul><ul><li>b. inhibition by metabolic products of other organisms </li></ul><ul><li>3. Bacterial adherence </li></ul><ul><li>--presence of pili or fimbriae </li></ul>
  6. 6. ORIGIN OF NORMAL FLORA <ul><li>1. Healthy fetus </li></ul><ul><ul><li>-- sterile until birth membrane ruptures </li></ul></ul><ul><ul><li>2. During and after birth </li></ul></ul><ul><ul><li>-- flora of mother’s genital tract </li></ul></ul><ul><ul><li>-- skin and respiratory tract </li></ul></ul><ul><ul><li>-- environment </li></ul></ul>
  7. 7. NORMALLY STERILE IN BODY (NO FLORA) <ul><li>1. Blood </li></ul><ul><li>Body Fluids </li></ul><ul><ul><li>CSF, urine </li></ul></ul><ul><li>3. Tissues </li></ul><ul><ul><li>Urinary bladder </li></ul></ul><ul><ul><li>Uterus </li></ul></ul><ul><ul><li>Fallopian tubes </li></ul></ul><ul><ul><li>Middle and inner ear </li></ul></ul><ul><ul><li>Paranasal sinuses </li></ul></ul>
  8. 8. NORMAL FLORA OF THE DIFFERENT SITES <ul><li>1. Skin </li></ul><ul><li>- flora are most abundant in moist areas </li></ul><ul><li>- aerobic and anaerobic diptheroids Ex. Corynebacterium </li></ul><ul><li>- non-hemolytic aerobic and anaerobic staphylococci </li></ul><ul><li>- alpha hemolytic streptococci, enterococci </li></ul><ul><li>- Gram(-) coliform bacilli and acinetobacter </li></ul><ul><li>- Fungi and yeast </li></ul><ul><li>Factors that eliminate non-resident MO from the skin </li></ul><ul><li>a. fatty acids in sebaceous secretions </li></ul><ul><li>b. presence of lysozyme </li></ul>
  9. 9. <ul><li>2. Respiratory tract </li></ul><ul><li>a. Upper respiratory tract (Nasopharynx) </li></ul><ul><li>-- same as oral organisms </li></ul><ul><li>-- transient carriage of: S. pneumonia, Hemophilus </li></ul><ul><li>b. Lower respiratory tract </li></ul><ul><li>--usually free of microbes </li></ul><ul><li>3. Eyes: Conjunctival Sac </li></ul><ul><li>-- very scanty, usually non-pathogenic bacteria </li></ul><ul><li>-- contain lysozyme </li></ul><ul><li>-- organisms: </li></ul><ul><ul><ul><li>Corynebacterium </li></ul></ul></ul><ul><ul><ul><li>Moraxella </li></ul></ul></ul><ul><ul><ul><li>Staphylococcus epidermis </li></ul></ul></ul><ul><ul><ul><li>non-hemolytic Streptococcus </li></ul></ul></ul>
  10. 10. <ul><li>4. Digestive Tract </li></ul><ul><li>a. Mouth — tongue and buccal mucosa </li></ul><ul><ul><ul><li>Streptococcus viridans </li></ul></ul></ul><ul><ul><ul><li>Neisseria sp </li></ul></ul></ul><ul><ul><ul><li>Branhamella sp </li></ul></ul></ul><ul><ul><ul><li>Candida albicans occasionally </li></ul></ul></ul><ul><li>-- Gingival crevices and tonsillar crypts </li></ul><ul><ul><ul><li>anaerobic flora </li></ul></ul></ul><ul><ul><ul><li>Bacteroides sp </li></ul></ul></ul><ul><ul><ul><li>Treponemes </li></ul></ul></ul><ul><ul><ul><li>Clostridia </li></ul></ul></ul><ul><li>b. Esophagus — transient mouth flora </li></ul><ul><li>c. Stomach – rapidly becomes sterile after meals </li></ul><ul><li>d. Small intestine – scanty resident flora except in the lower ileum. </li></ul><ul><ul><ul><li>Ex. Streptococcus, lactobacilli, Yeast (candida) </li></ul></ul></ul>
  11. 11. <ul><li>e. Colon </li></ul><ul><ul><li>largest number of microbes (400 species) </li></ul></ul><ul><ul><li>anaerobes: 96-99% </li></ul></ul><ul><ul><ul><li>Bacteroides </li></ul></ul></ul><ul><ul><ul><li>anaerobic Lactobacilli </li></ul></ul></ul><ul><ul><ul><li>Clostridium sp </li></ul></ul></ul><ul><ul><li>Facultative: 1-4%: </li></ul></ul><ul><ul><ul><li>E. coli, Proteus sp , Pseudomonas sp, Candida sp </li></ul></ul></ul><ul><ul><li>Breastfed babies: 99% </li></ul></ul><ul><ul><ul><li>anaerobic Bifidobacterium sp </li></ul></ul></ul><ul><ul><li>Artificially fed babies </li></ul></ul><ul><ul><ul><li>Lactobacillus acidophilus </li></ul></ul></ul>
  12. 12. <ul><li>5. Genito-urinary tract: urinary tract </li></ul><ul><ul><li>sterile above the distal 1 cm of the urethra </li></ul></ul><ul><li>vagina </li></ul><ul><ul><li>before puberty and post menopausal stage </li></ul></ul><ul><ul><ul><li>derived from flora of skin and colon </li></ul></ul></ul><ul><ul><li>child bearing age </li></ul></ul><ul><ul><ul><li>Lactobacilli, yeast </li></ul></ul></ul>
  13. 13. BENEFICIAL EFFECTS OF NORMAL FLORA <ul><li>1. Production of essential nutrients </li></ul><ul><li>-- Intestinal flora - synthesize Vitamin K & Vit. B complex </li></ul><ul><li>2. Defense against microbial pathogens </li></ul><ul><li>a. Bifidobacteria and breastfeeding </li></ul><ul><li>-- inhibit colonization of enteric pathogens </li></ul><ul><li>b. Vaginal flora (Lactobacillus) </li></ul><ul><li>-- provides protection vs gonococcal vulvovaginitis </li></ul><ul><li>c. Prolonged antibiotic treatment alter GIT </li></ul><ul><li>-- Candida sp diarrhea </li></ul><ul><li>-- S. aureus necrotizing enterocolitis </li></ul><ul><li>-- C. difficile pseudomembranous colitis </li></ul>
  14. 14. HARMFUL EFFECTS: OPPORTUNISTIC INFECTION <ul><li>-- Local or generalized host defense mechanisms are compromised </li></ul><ul><li>-- flora reaches protected areas of body in sufficient numbers </li></ul><ul><li>-- E. coli -> ascend urethra -> caused UTI </li></ul><ul><li>-- Colon perforation -> feces in peritoneal cavity (peritonitis) </li></ul><ul><li>-- Viridians strep -> blood -> cause bacteremia + physiologic trauma or injury -> colonize previously damaged valves ->causing bacterial endocarditis </li></ul>
  15. 15. DEFINITION OF TERMS <ul><li>PATHOGENESIS </li></ul><ul><li>is the steps or mechanisms involved in the development of the disease </li></ul><ul><li>PATHOGENICITY </li></ul><ul><li>is the ability to cause disease </li></ul><ul><li>PATHOGEN </li></ul><ul><li>a microorganism capable of causing disease </li></ul><ul><li>PATHOLOGY </li></ul><ul><li>is the study of the structural and functional manifestations of the disease </li></ul>
  16. 16. Infection Versus Infectious Disease <ul><li>Infectious Disease </li></ul><ul><li>-is a disease caused by a microbe and the microbes that cause infectious disease are collectively referred to as pathogens . </li></ul><ul><li>Infection </li></ul><ul><li>- according to many microbiologists, infection means colonization by a pathogen . </li></ul>
  17. 17. MICROBES VS HUMANS <ul><li>DEFINITION </li></ul><ul><li>SYMPTOMS </li></ul><ul><li>-- evidence of disease that is experienced or perceived </li></ul><ul><li>-- subjective changes in body function noted by patient but not apparent to an observer </li></ul><ul><li>SIGNS </li></ul><ul><li>-- objective evidence of a disease the physician/nurse can observe and measure </li></ul><ul><li>SYNDROME </li></ul><ul><li>-- a specific group of signs and symptoms that accompany a particular disease. </li></ul>
  18. 18. <ul><li>INCIDENCE </li></ul><ul><li> -- number of people in a population who develop a disease during a particular time period. </li></ul><ul><li>PREVALENCE </li></ul><ul><li> -- the number of people in a population who develop a disease regardless of when it appeared </li></ul><ul><li> -- both old and new cases </li></ul>
  19. 19. CLASSIFICATION OF INFECTIOUS DISEASES <ul><li>BASED ON BEHAVIOR WITHIN THE HOST: </li></ul><ul><li>1. Communicable Disease </li></ul><ul><li>-- any disease that spreads from one host to another either directly or indirectly </li></ul><ul><li>-- contagious disease -> disease that easily spreads from one person to another. </li></ul><ul><li>2. Non-communicable disease </li></ul><ul><li>-- not spread from one host/person to another </li></ul>
  20. 20. BASED ON OCCURRENCE OF DISEASE <ul><li>Sporadic disease </li></ul><ul><li>-- disease occurs only occassionally </li></ul><ul><li> ex. Botulism, tetanus </li></ul><ul><li>Endemic disease </li></ul><ul><li>-- constantly present in a population, community or country. </li></ul><ul><li>ex. TB, malaria </li></ul><ul><li>Epidemic disease </li></ul><ul><li>-- acquire disease in a relatively short period </li></ul><ul><li>-- greater than normal number of cases in an area within a short period of time. </li></ul><ul><li>ex. dengue </li></ul><ul><li>Pandemic disease </li></ul><ul><li>-- epidemic disease that occurs worldwide Ex. HIV </li></ul>
  21. 21. BASED ON SEVERITY OR DURATION OF DISEASE <ul><li>Acute disease </li></ul><ul><li>-- develops rapidly (rapid onset) lasts only a short time </li></ul><ul><li> Ex. Measles, mumps, influenza </li></ul><ul><li>Chronic disease </li></ul><ul><li>– develops slowly (insidious onset) </li></ul><ul><li>-- disease is likely to be continual or recurrent for long </li></ul><ul><li>periods </li></ul><ul><li>Ex. TB, leprosy </li></ul><ul><li>Subacute disease </li></ul><ul><li>– intermediate between acute and chronic. </li></ul><ul><li>Ex. Bacterial endocarditis </li></ul><ul><li>Latent disease </li></ul><ul><li>- causative agent remains inactive for a time but then becomes active to produce symptoms of the disease. </li></ul><ul><li>Ex. Chickenpox  Shingles (Zoster) </li></ul>
  22. 22. Stages of syphilis <ul><li>Syphilis infection (3 weeks) </li></ul><ul><li> </li></ul><ul><li>Primary: Chancre (2-6 months) </li></ul><ul><li> </li></ul><ul><li>Secondary: Rash, lesions, fever, hair loss (2-6 months) </li></ul><ul><li> </li></ul><ul><li>Latent Stage: No symptoms (5-10 years) </li></ul><ul><li> </li></ul><ul><li>Tertiary: Destruction of brain, heart, spinal cord, and/or other organs </li></ul>
  23. 23. Symptoms of a Disease Versus Signs of a Disease <ul><li>SYMPTOM OF A DISEASE </li></ul><ul><li>- some evidence of a disease that is </li></ul><ul><li>experienced or perceived by the patient. </li></ul><ul><li> Asymptomatic disease (clinical disease) </li></ul><ul><li>-a disease in which the patient is experiencing </li></ul><ul><li>symptoms </li></ul><ul><li> Symptomatic disease (subclinical disease) </li></ul><ul><li>-a disease that the patient is unaware of because she/he </li></ul><ul><li>is not experiencing any symptoms. </li></ul><ul><li>SIGN OF A DISEASE </li></ul><ul><li>- some type of objective evidence of a disease </li></ul>
  24. 24. BASED ON EXTENT OF AFFECTED HOST’S BODY <ul><li>Local infection </li></ul><ul><li>-- microbes invade a relatively small area of the body. </li></ul><ul><li>Generalized (Systemic) Infection </li></ul><ul><li>-- spread throughout the body by blood or lymph </li></ul><ul><li>ex. Measles, chicken pox </li></ul><ul><li>Focal Infection </li></ul><ul><li>-- local infection that spread but are confined to specific areas of the body. </li></ul>
  25. 25. BASED ON STATE OF HOST RESISTANCE <ul><li>Primary Infection </li></ul><ul><li>-- acute infection that causes the initial illness </li></ul><ul><li>Secondary infection </li></ul><ul><li>-- one caused by an opportunistic pathogen after the primary infection has weakened the body’s defenses. </li></ul><ul><li>Subclinical (Inapparent) Infection </li></ul><ul><li>-- does not cause any noticeable illness. </li></ul>
  26. 26. WHY INFECTIONS DOES NOT ALWAYS OCCCUR <ul><li>The microbe may land at an anatomical site where it is unable to multiply </li></ul><ul><li>Many pathogens must attach to specific receptor site before they are able to multiply and cause damage </li></ul><ul><li>Antibacterial factors that destroy or inhibit the growth of microbes maybe present at the site where the pathogen lands </li></ul><ul><li>The indigenous microflora at the site may inhibit growth of the foreign microbe by occupying space and using up the available nutrients </li></ul><ul><li>The indigenous microflora at the site may produce antibacterial factors (bacteriocins) that destroy the newly arrived pathogen. </li></ul><ul><li>The individuals nutritional and overall health status often influences the outcome of the pathogen/host encounter </li></ul><ul><li>The person maybe immune to that particular pathogen as a result of prior infection or vaccination </li></ul><ul><li>Phagocytic white blood cells may engulf and destroy before it has an opportunity to multiply, invade and cause disease </li></ul>
  27. 27. FACTORS IN DISEASE DEVELOPMENT (CHAIN OF INFECTION) <ul><li>Source of Infection (the pathogen) </li></ul><ul><li>Reservoir </li></ul><ul><li>Portal of exit </li></ul><ul><li>Mode of transmission </li></ul><ul><li>5. Portal of entry </li></ul><ul><li>6. Susceptible host </li></ul>
  28. 28. <ul><li>FACTORS PERTAINING TO PATHOGEN: </li></ul><ul><li>Virulence of pathogen </li></ul><ul><li>Portal of entry </li></ul><ul><li># of organisms that enter the body </li></ul><ul><li>FACTORS PERTAINING TO HOST: </li></ul><ul><li>Health status </li></ul><ul><li>Nutritional status </li></ul><ul><li>Age, lifestyle, SE level, travel, hygiene, subs. abuse & immune status </li></ul>
  29. 29. STAGES OF DISEASE <ul><li>INCUBATION PERIOD </li></ul><ul><ul><li>is the time that elapses between the arrival of the pathogen and the onset of symptoms. </li></ul></ul><ul><li>FACTORS INFLUENCING THE INCUBATION PERIOD: </li></ul><ul><li>Overall health and nutritional status of the host </li></ul><ul><li>Virulence of the pathogen </li></ul><ul><li>Numbers of the pathogens that enters the body </li></ul>
  30. 30. STAGES OF DISEASE <ul><li>Incubation Period </li></ul><ul><li>- time interval between initial infection and 1 st Appearance of any s/sx </li></ul><ul><li>Prodromal period </li></ul><ul><li>— early, mild symptoms of disease </li></ul><ul><li>Period of illness </li></ul><ul><li>--- overt s/sx of disease </li></ul><ul><li>--- WBC may increase or decrease </li></ul><ul><li>--- result to death if immune responses and/or medical treatment fails </li></ul><ul><li>Period of decline </li></ul><ul><li>— s/sx subside </li></ul><ul><li>--- vulnerable to secondary infection </li></ul><ul><li>Period of convalescence </li></ul><ul><li>--- regains strength and body returns to </li></ul><ul><li>pre-diseased state </li></ul><ul><li>--- recovery has occurred </li></ul>
  31. 31. The course of an infectious disease <ul><li>Exposure to pathogen </li></ul><ul><li> </li></ul><ul><li>Incubation Period </li></ul><ul><li> </li></ul><ul><li>Prodromal Period </li></ul><ul><li> </li></ul><ul><li>Period of Illness </li></ul><ul><li>Convalescence    Death </li></ul><ul><li>Disability </li></ul>
  32. 32. THE SOURCE OF INFECTION (THE PATHOGEN) <ul><li>DEFINITION </li></ul><ul><li>PATHOGENECITY </li></ul><ul><li>- capability of a pathogen to cause disease </li></ul><ul><li>- factors: 1. Ability to infect host </li></ul><ul><li> 2. Protect from body’s defenses </li></ul><ul><li> 3. Invade and multiply in tissues </li></ul><ul><li> 4. Cause damage or destruction to tissues </li></ul><ul><li>VIRULENCE </li></ul><ul><li>- Measure or degree of pathogenecity </li></ul>
  33. 33. <ul><li>VIRULENCE FACTORS </li></ul><ul><li>1. Bacterial Structures </li></ul><ul><li>a. Flagella </li></ul><ul><li>- enable bacteria to invade aqueous areas of </li></ul><ul><li>the body. </li></ul><ul><li>b. Capsules </li></ul><ul><li>- enable bacteria to attach to tissues </li></ul><ul><li>-- anti-phagocytic function </li></ul><ul><li>-- ex. Streptococcus pneumoniae </li></ul><ul><li>c. Pili (Fimbriae) </li></ul><ul><li>-- enable bacteria to adhere to tissues </li></ul><ul><li>-- ex. E. coli, V. cholerae, Neisseria sp </li></ul>
  34. 34. <ul><li>2. Enzymes (Exoenzymes) </li></ul><ul><li>- enzymes = are proteins that increases the rate of chemical reaction </li></ul><ul><li>a. Coagulase– ex. S. aureus </li></ul><ul><li>clots plasma </li></ul><ul><li>↓ </li></ul><ul><li>forms fibrin clot </li></ul><ul><li>↓ </li></ul><ul><li>protection from phagocytosis </li></ul><ul><li>b. Kinases (Fibrinolysins) </li></ul><ul><li>--lyse /dissolve clots & allows spread of organism </li></ul><ul><li>c. Hyaluronidase (the spreading factor) </li></ul><ul><li>--allows bacteria to spread through tissues by breaking down hyaluronic acid (“cement”) </li></ul><ul><li>--ex. Staphylococcus, streptococcus, clostridium </li></ul>
  35. 35. 2. Enzymes (Exoenzymes) <ul><li>d. Collagenase </li></ul><ul><li>- ex. Clostridium perfringens </li></ul><ul><li>- breaks down collagen in skin, tendons, cartilage and bones </li></ul><ul><li>e. Hemolysins </li></ul><ul><li>- cause damage(lysis) to host’s RBC </li></ul><ul><li>- important in identification of organism (alpha or beta hemolytic) </li></ul><ul><li>f. Lecithinase </li></ul><ul><li>- ex. Clostridium perfringens </li></ul><ul><li>- breaks down phospholipids (lecithin) found in membranes of RBC and other tissues. </li></ul>
  36. 36. <ul><li>3. Toxins (Poisonous Substances) </li></ul><ul><li>a. Endotoxin: Lipopolysaccharide (LPS) </li></ul><ul><li>--part of outer portion of cell wall of gram (-) bacteria </li></ul><ul><li>--can cause pyrogenic response </li></ul><ul><li>-- ex. Typhoid fever, UTI, meningitis </li></ul><ul><li>b. Exotoxins </li></ul><ul><li>- produced inside mostly Gram (+) bacteria </li></ul><ul><li>- can cause damage to the host by destroying cells or disrupting normal cellular metabolism </li></ul><ul><ul><ul><li>- a soluble protein that can be excreted by all of the following organisms except viruses </li></ul></ul></ul><ul><li>--ex. Diphtheria toxin, botulinum toxin, tetanus toxin </li></ul><ul><li>--leukocidin ->toxins that destroy WBC </li></ul><ul><li>--neurotoxin-> toxins that affect CNS (botulinum toxin) </li></ul><ul><li>-- enterotoxins -> toxins that affect GIT </li></ul><ul><li>ex. E.coli, V. cholerae </li></ul>
  37. 37. MECHANISMS BY WHICH PATHOGENS ESCAPE IMMUNE RESPONSES <ul><li>ANTIGENIC VARIATION </li></ul><ul><li>- pathogens able to periodically change their surface antigens. Ex are influenza viruses, HIV, Neisseria gonorrhea , trypanosomes </li></ul><ul><li>CAMOUFLAGE AND MOLECULAR MIMICRY </li></ul><ul><li>- adult schistosomes are able to conceal their foreign nature by coating themselves with host proteins. In molecular mimicry, the pathogen’s surface closely resemble host antigens and are therefore not recognized as foreign </li></ul><ul><li>DESTRUCTION OF ANTIBODIES </li></ul><ul><li>- H. influenza. Neisseria gonorrhea and streptococci produce an enzyme IgA protease that destroys IgA antibody </li></ul>
  38. 38. EPIDEMIOLOGY AND DISEASE TRANSMISSION <ul><li>RESERVOIRS OF INFECTIONS </li></ul><ul><li>--any site where the pathogen can multiply or merely survive until it is transferred to the host. </li></ul><ul><li>1. Human Reservoir </li></ul><ul><li>- principal living reservoir of human disease </li></ul><ul><li>a. direct transmission </li></ul><ul><li> --with signs and symptoms of disease and transmit the disease </li></ul>
  39. 39. <ul><li>b. Carriers </li></ul><ul><li>— harbor the pathogens but have no s/sx </li></ul><ul><li>b.1 incubatory carriers </li></ul><ul><li>- capable of transmitting a pathogen during the incubation period </li></ul><ul><li>b.2 convalescent carriers </li></ul><ul><li>- transmit disease during convalescence or recovery period. </li></ul><ul><li>b.3 active carriers </li></ul><ul><li>- completely recovered from disease but continue to harbor the pathogen indefinitely </li></ul><ul><li>b.4 passive carriers </li></ul><ul><li>- carry the pathogen without ever having the disease. </li></ul>
  40. 40. <ul><li>2. Animal Reservoir </li></ul><ul><li>ZOONOSES </li></ul><ul><ul><li>infectious diseases that humans acquire from animal sources </li></ul></ul><ul><ul><li>150 zoonoses </li></ul></ul><ul><li>Routes: </li></ul><ul><li>a. direct contact </li></ul><ul><ul><ul><ul><li>with infected animal or with domestic pet waste </li></ul></ul></ul></ul><ul><li>b. Inhalation </li></ul><ul><ul><ul><ul><li>from contaminated hides, fur, feathers </li></ul></ul></ul></ul><ul><li>c. Ingestion </li></ul><ul><ul><ul><ul><li>contaminated food and water </li></ul></ul></ul></ul><ul><ul><ul><ul><li>consumption of infected animal products </li></ul></ul></ul></ul><ul><li>d. Injection of the pathogen </li></ul><ul><ul><ul><ul><li>insect vectors </li></ul></ul></ul></ul>
  41. 41. Zoonoses are Human Diseases with Animal Reservoirs.
  42. 42. <ul><li>3. Inanimate (Non-Living) Reservoirs </li></ul><ul><li>--air, soil, food, milk, water, fomites </li></ul><ul><li>FOMITES </li></ul><ul><li>--articles that are easily contaminated by pathogens from the respiratory tract, intestinal tract and skin </li></ul><ul><li>AIR </li></ul><ul><li>--droplets of respiratory tract secretions </li></ul><ul><li>--dust particles </li></ul>
  43. 43. MODE OF DISEASE TRANSMISSION <ul><li>1 Contact transmission </li></ul><ul><ul><li>-- spread of an agent of disease by direct, indirect or droplet transmission </li></ul></ul><ul><ul><li>Direct Contact Transmission </li></ul></ul><ul><ul><li>--person to person transmission of an agent by physical contact between its source and susceptible host </li></ul></ul><ul><ul><li>--no intermediate object involved </li></ul></ul><ul><ul><li>--touching, kissing, sexual intercourse </li></ul></ul><ul><ul><li>--SOURCE : SUSCEPTIBLE HOST </li></ul></ul>
  44. 44. <ul><ul><li>b. Indirect Contact Transmission </li></ul></ul><ul><ul><li>--reservoir to a susceptible host by means of a non-living object (fomites) </li></ul></ul><ul><ul><li>--source : non-living object, susceptible host </li></ul></ul><ul><ul><li>c. Droplet Transmission </li></ul></ul><ul><ul><li>--microbes spread in droplet nuclei that travel only short distances (<1 meter) </li></ul></ul><ul><ul><li>-- ex. Coughing, sneezing, laughing or talking </li></ul></ul>MODE OF DISEASE TRANSMISSION
  45. 45. <ul><li>2. Vehicle Transmission </li></ul><ul><li>--transmission of disease agents by a medium. Ex. H20, food, air, blood and other body fluids, drugs and IV fluids) </li></ul><ul><li>a. Waterborne transmission </li></ul><ul><li>-- H20 contaminated with untreated or poorly treated sewage </li></ul><ul><li>ex. Cholera, Shigella </li></ul><ul><li>b. Foodborne transmission </li></ul><ul><li>-- transmitted by foods that are incompletely cooked, poorly refrigerated or prepared under unsanitary conditions. Ex. Food poisoning, tapeworm infection </li></ul><ul><li>c. Airborne transmission </li></ul><ul><li>--spread of agents of infection by droplet nuclei in dust that travel. < 1 meter </li></ul><ul><li>3. Vectors </li></ul><ul><li>— animals that carry pathogens from one host to another </li></ul>
  46. 46. STEPS IN THE PATHOGENESIS OF INFECTIOUS DISEASES <ul><li>ENTRY of the pathogen into the body. </li></ul><ul><li>ATTACHMENT of the pathogen to some tissues within the body. </li></ul><ul><li>MULTIPLICATION of the pathogen. </li></ul><ul><li>INVASION/SPREAD OF THE PATHOGEN </li></ul><ul><li>EVASION OF HOST DEFENSES </li></ul><ul><li>DAMAGE TO HOST </li></ul>
  47. 47. CONTROL OF EPIDEMIC DISEASE <ul><li>Report cases of communicable diseases to proper agencies </li></ul><ul><li>Public education </li></ul><ul><li>Identification and eliminated reservoirs of infection </li></ul><ul><li>Isolate diseased persons </li></ul><ul><li>Participate in immunizing programs </li></ul><ul><li>Help to treat sick persons </li></ul>