Infectious Disease Process Biomed 2004

But first……a little review Koch Leeuwenhoek Pasteur Lister Jenner

Leeuwenhoek: microorganisms / microscope Koch: proved specific organisms cause certain diseases / anthrax, tuberculosis Jenner: smallpox vaccine Pasteur: pasteurized milk, rabies Lister: antiseptic

Definitions Disease: conditions impairing normal tissue function Microorganisms: small living plants or animals Nonpathogens: microorganisms that do not cause disease or infection Pathogens: cause disease and infection –Toxins waste product of pathogens that is poisonous to the human body

Microorganism Microbes are so small they can only be seen via a microscope They are everywhere: in us, on us, around us –Pathogen –Non-pathogen

Types of Microorganisms Bacteria Viruses Protozoa Fungi Parasites Prions (give me examples)

Non pathogens Processing of cheese, beer, yogurt Curing of leather Baking of bread Yogurt : live culture

Body Flora Different microorganisms live in communities on and in the body Organisms that are nonpathogenic and natural inhabitants of one part of the body become pathogenic when in another part of the body

More term’s Opportunist pathogens: potentially infectious agents that rarely cause disease in individuals with healthy immune systems Candidiasis (thrush is a fungal infection of the mouth, throat or vagina) frequently caused by antibiotics

AIDS Cancer medications Antibiotics Other medical problems or infections Stress Malnutrition Lack of sleep

Nature of infectious diseases Bacteria can be a resident of the body and cause no harm: –Unless it goes somewhere it shouldn't –You have to many of the organism –The body defenses are to weak –And it can be transmitted to others

E COLI FAVORITE HANGOUT: –Large intestine LIKES: Producing Vitamin K (essential for normal blood clotting) Helping to digest food –But when it enters other areas……problems!

E coli gone bad! First recognized as a cause of illness in 1982 during an outbreak of severe bloody diarrhea; the outbreak was traced to contaminated hamburgers. Since then, most infections have come from eating undercooked ground beef Eating meat, especially ground beef, that has not been cooked sufficiently to kill E. coli O157:H7 can cause infection. Contaminated meat looks and smells normal

Among other known sources of infection are consumption of sprouts, lettuce, salami, unpasteurized milk and juice, and swimming in or drinking sewage- contaminated water. Bacteria in stools of infected persons can be passed from one person to another if hygiene or handwashing habits are inadequate.

Diseases Causes severe bloody diarrhea and abdominal cramps In children under 5 years of age and the elderly, the infection can also cause a complication called hemolytic uremic syndrome, in which the red blood cells are destroyed and the kidneys fail. UTI’s Vaginal infections About one-third of persons with hemolytic uremic syndrome have abnormal kidney function many years later, and a few require long-term dialysis. Another 8% of persons with hemolytic uremic syndrome have other lifelong complications, such as high blood pressure, seizures, blindness, paralysis, and the effects of having part of their bowel removed.

Contagious / Virulent Some infectious diseases are easily transmitted (contagious) but are not likely to cause disease (not very virulent) –Polio: infects majority who come in contact with it, but only 5-10 % develop polio Other infectious diseases are very virulent, but not very contagious –Ebola hemorrhagic fever: 50-90% fatality among those infected, but not transmitted via casual contact

How Microorganisms Grow Moisture Warmth Oxygen Darkness Food

Pathogens Microorganism that causes disease

Transmission Direct contact Airborne Droplet Common vehicle Vector borne

Discuss the infectious disease process Source or agent Reservoir or host Portal of exit Method of transmission Portal of entry Susceptible host

Infection: results when a pathogen invades and begins growing within a host Disease : results only if an when (as a result of the invasion and growth of a pathogen) tissue function is impaired.

The body has defense mechanisms to prevent infection Physical Barrier is the body’s Main Line of Defense Mechanical factors Chemical factors See handout

Endogenous: infection originating in ones own body Exogenous: infection originating from out side of the body

In order to cause disease, pathogens must be able to enter, adhere, invade, colonize and inflict damage

Entrance to host Mouth Eyes Genital opening Wounds Mother - child

Growth of pathogens or the production of toxins/enzymes cause disease Toxins waste product of pathogens that is poisonous to the human body