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- 1. Host-microbe relationships Diseaseprocesses Epidemiology Nosocomial infections Introduction to Immunity
- 2. Host-Microbe Relationships Whatdo the following terms mean? Pathogen Host Symbiosis Symbiosis includes: mutualism commensalism parasitism
- 3. Example of Mutualism: Bacteria on The Human Skin
- 4. Contamination, Infection, &Disease Contamination : the presence of microbes Infection : the multiplication of any parasitic organism in or on a host Disease : a change in the state of health in which tissues/organs are disrupted or damaged. Can be viewed as a sequence of increasing severity (contamination infection disease)
- 5. Pathogenicity vs. VirulencePathogenicity : the ability of an organism to cause disease Virulence : the intensity (or degree) to which an organism causes disease
- 6. Microflora (Flora, Microbiota)Organisms that live on or in the body but under normal circumstances do not cause disease Types: Resident microflora (normal flora): comprise microbes that are always present in or on the human body Transient microflora: microbes that can be present under certain conditions in any of the locations where resident microflora are found
- 7. Opportunistic Organisms Organisms that do not normally cause disease, but take advantage of particular opportunities to cause disease. Immunocompromised individuals commonly become infected with opportunistic organisms
- 8. Kinds of DiseasesHuman diseases are caused by infectious agents, structural or functional genetic defects, environmental factors, or any combination of these causes Infectious Diseases: caused by infectious agents such as bacteria, viruses, fungi, protozoa, & helminths Noninfectious Diseases: caused by any factor other than infectious organisms
- 9. Microbiology focuses onInfectious Diseases Communicable disease : a disease that can be transmitted from one person to another What are examples of communicable microbial diseases? Noncommunicable disease : a disease that cannot be transmitted from one person to another What are examples of noncommunicable microbial diseases?
- 10. Types of InfectiousDiseases Acute : develops rapidly & runs its course quickly (measles & cold) Chronic : develops more slowly than an acute disease, is usually less severe, & persists for a long, indeterminate period (tuberculosis) Subacute : intermediate between an acute & a chronic disease (gingivitis) Latent : characterized by periods of inactivity either before signs & symptoms appear (herpes virus)
- 11. Stages of anInfectious Disease Incubation period: time between infection & appearance of signs and symptoms Prodromal phase: a short period of nonspecific, often mild, symptoms (malaise and headache) Invasive phase: period when the individual experiences the typical signs & symptoms of the disease Acme : period during invasive phase where symptoms & signs are most severe Decline phase: the period of illness when host defenses & effects of treatment overcome the pathogen Convalescent period: tissues are repaired, healing takes place, & body regains strength & recovers
- 12. Stages of anInfectious Disease
- 13. Signs, Symptoms, &Syndromes Most diseases are recognized by signs & symptoms Sign : a characteristic of a disease that can be observed by examining the patient (e.g. swelling, redness, rashes, coughing, pus, runny nose, vomiting) Symptom : a characteristic of a disease that can be observed or felt only by the patient (e.g. pain, shortness of breath, nausea, sore throat, headache) Syndrome : a combination of signs & symptoms occurring together & are indicative of a particular disease or abnormal condition Sequelae : even after recovery, some diseases leave after-effects (e.g. valve damage)
- 14. Epidemiology, Incidence &Prevelance Epidemiology : the study of factors & mechanisms involved in the frequency & spread of diseases & health-related problems Etiology : the assignment or study of causes and origins of a disease Incidence of a disease: the number of new cases contracted within a set population during a specific period of time Prevalence of a disease: the total number of people infected within the population at any time
- 15. Diseases in PopulationsEndemic : disease is present continually in the population of a particular geographic area Epidemic : a higher-than-normal incidence of a disease in a population Pandemic : worldwide disease
- 16. The Spread ofCholera Began in Peru in 1991 Moved to Columbia & Ecuador Late 1992: epidemic spread to Venezuela, Bolivia, Chile, & Brazil in South America Then to Guatemala, Honduras, Panama, Nicaragua, & El Salvador in Central America
- 17. Reservoirs of InfectionReservoirs: Sites in which organisms can persist & maintain their ability to infect Essential for new human infections to occur Humans Other animals (including insects) Plants Certain nonliving material (water & soil) Zoonoses: diseases that can be transmitted under natural conditions to humans from other vertebrate animals (rabies)
- 18. Modes of DiseaseTransmission- Contact Transmission direct contact indirect contact (fomites) droplets
- 19. Modes of DiseaseTransmission- Vehicle transmission water air food
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- 21. Modes of DiseaseTransmission- Vector transmission mechanical biological
- 22. Controlling Disease TransmissionIsolation : A patient with a communicable disease is prevented from having contact with the general population Quarantine : the separation of âhealthyâ human or animal carriers from the general population when they have been exposed to a communicable disease
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- 24. Modes of DiseaseTransmission- Summary Contact Transmission Can be direct, indirect, or by droplets Direct contact requires body contact between individuals Indirect contact occurs through fomites Droplet: occurs when a person coughs, sneezes, or speaks near others Vehicle Transmission Nonliving carrier of an infectious agent from its reservoir to a susceptible host Water Air Food Vector-Borne Transmission Vectors: Living organisms that transmit disease to humans Most vectors are arthropods: ticks, flies, fleas, lice & mosquitoes
- 25. How Fungi & Protozoa Cause Disease Fungi Spores that are inhaled or enter cells through a cut or wound Some fungi produce mycotoxins Protozoa invade & reproduce in red blood cells attach to tissues & digest them Produce cysts (dormant forms) as a means of disease transmission & trophozoites (active, multiplying forms)
- 26. Factors Affecting DiseaseEstablishment Portal of Entry Adhesive Factors Dose Tissue Penetration Enzymes Toxins Toxins, enzymes, & adhesive factors are sometimes referred to as virulence factors
- 27. Portal of EntrySite of entry of microbes Includes skin, mucous membranes, openings of the respiratory, digestive, & genitourinary systems, & crossing the placenta May involve adhesive factors, also known as adhesins (include certain surface proteins/ glycoproteins, fimbriae, & capsules)
- 28. Portals of Exitsites where microbes leave the body
- 29. Dose The numberof infective particles required to lead to colonization Colonization refers to the growth & reproduction of microorganisms on host tissues Exposure to a low dose can result in immunity
- 30. Tissue Penetration The ability of a microbe to enter host tissue Visible in tissue preparation Not required for every disease The ability of a microbe to invade tissue & damage it is known as its invasiveness
- 31. Enzymes Coagulase StreptokinaseHyaluronidase Hemolysins Leukocidin Collagenase
- 32. Coagulase : clotsfibrin in blood plasma. Bacteria form a fibrin clot around themselves protecting them the hostâs immune system ( S. aureus ) Streptokinase : dissolves fibrin clots ( Streptococcus ) Enzymes
- 33. Hyaluronidase: enzymedigests hyaluronic acid Enzymes
- 34. Hemolysins: enzymesthat breakdown red blood cells (RBCs) 3 Types of hemolysis : 1- Gamma hemolyis : no breakdown of RBCs 2- Alpha ( ďĄ ): partial breakdown of RBCs; greenish-grey coloration 3- Beta or complete hemolysis ( ď˘ ): complete breakdown of RBCs; clear zones around colonies Alpha Beta Streptococcus pneumoniae Streptococcus pyogenes Enzymes
- 35. Enzymes Collagenase : enzyme that degrades collagen ( Clostridium ) Leukocidin : enzyme that degrades white blood cells
- 36. Bacterial Toxins Asubstance that is poisonous to another organism Two types: Exotoxin : a toxin produced by a cell & is secreted outside the cell to affect host tissue Endotoxin : a toxin that is a portion of the cell (usually the cell wall) & is released into host tissues Characteristic of Gram negative bacteria
- 37. Nosocomial Infections : a n infection acquired in a hospital or other medical facility Where do the bacteria causing nosocomial infections come from? Common Causative Agents of Nosocomial Infections
- 38. Some Common Modesof Transmission of Nosocomial Infections
- 39. Relative Frequencies ofSites of Nosocomial Infections
- 40. Latex gloves Eyeprotection Mask Sterile Equipment Infection Control