Microorganisms and Disease How does the human body and various microorganisms interact in terms of disease?

Infectious Disease bacteria can produce capsules, enzymes, and toxins infectious disease is the primary cause of death world-wide 1918-1919: influenza pandemic killed more than 20 million people world-wide and 500,000 people in the United States

Readings question #1: Describe the “chain of infection”.

Infection vs. Disease Infection: “the entry, establishment and multiplication of pathogenic organisms within a host” Disease: an abnormal state in which part or all of the body is not properly adjusted or is incapable of performing normal functions; any change from a state of health

Factors that Influence the Occurrence of Disease 1) virulence of the organisms 2) portal of entry of the pathogen 3) number of organisms present 4) the resistance of the host

Virulence of Organisms virulence: “relative power of an organism to produce disease” contamination: “the act of introducing disease germs or infectious material into an area or substance”

Virulence (cont’d) pathogenicity: “the state of producing or being able to produce pathological changes and disease”

Types of Infections and Diseases acute diseases: symptoms develop rapidly but may only last for a short period of time chronic diseases: develop slowly and are likely to continue for long periods of time

Factors Influencing Virulence Capsules and Endospores

Sources of Infection Human Reservoirs: Animal Reservoirs: Environmental Reservoirs:

Portal of Entry 5 portals of entry: 1) skin and mucous membranes 2) respiratory tract 3) digestive tract 4) genito-urinary tract 5) placenta

Resistance of the Host mechanical defenses physiological defenses chemical defenses

Mechanical Defenses Skin: epithelium (epidermis), sebaceous glands, dryness, “necrobiosis” Eyes: lacrimal apparatus Saliva: cleansing action Respiratory Tract: mucus, ciliated epithelium Urinary Tract: flushing action

Physiological Defenses Inflammation: pus Fever: 102-104 degrees Phagocytosis: phagocyte ingests material

Chemical Defenses Lysozome: enzyme that breaks down cell walls of bacteria Sebum: sebaceous glands, oily substance, protective film, lowers skin pH Gastric Juice: HCl, enzymes, mucus, acidic

Antigens “a foreign substance that stimulates the formation of antibodies that react specifically with it” substance that provoke a specific response Antibodies: “glycoprotein substance developed by the body in response to, and interacting specifically, with an antigen. Also known as immunoglobulin.”

Antigen-Antibody Reactions 1) destroy pathogens by neutralizing the toxins the pathogen produces 2) coat the pathogen with a substance that attracts phagocytes by forming a substance that clumps the antigens together 3) prevent the pathogen from adhering to the body’s cells

Types of Immunity Natural (Innate) Acquired: Naturally Acquired – active, passive Artificially Acquired - active: vaccines - passive: antibodies immune serums