bio 315 chapter 15

bio 315 chapter 15 - Chapter 15: Infection and Disease Part...

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Chapter 15: Infection and Disease Part 3: Microorganisms, Humans, and Disease If a microorganism or other agent (like a virus) has the capability of causing disease, we call it a pathogen . Infection refers to the successful invasion and growth of pathogens in the body. Disease refers to an abnormal state in which the body or one of its parts is incapable of performing its functions properly. An organism is said to have a disease when a pathogen overcomes the body’s defenses. (In other words, it’s possible to come into contact with pathogens and even have an infection without ultimately having a disease.) A host is an organism that shelters and/or supports the growth of pathogens. Disease caused by infective pathogens is referred to as “ infectious disease ” (as opposed to “degenerative”). Pathology Pathology is defined as the study of disease in an individual, and deals with… o Etiology (the cause of disease) o Pathogenesis (the development of disease over time in an individual) o Effects/treatments of disease The Normal Microbiota –Microbes That are “Supposed” to be There What is their normal relationship to a host organism? Humans (and other animals) are usually sterile before birth, after which they become colonized both internally and externally. Microbes that establish permanent residence either inside or on the body surface without causing disease are the normal microbiota (also called the resident flora). Unbelievably, it is estimated that the resident population of microbial cells outnumbers human cells by a factor of 10! Also, the normal microbiota contains members that are bacteria, fungi, and protozoa. Examples: o Gastrointestinal tract: Escherichia coli
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o Oral cavity (mouth): Various Streptococcus species o Skin: Various Staphylococcus species o Vaginal area: Lactobacillus, Candida (a yeast) It’s a Symbiotic Relationship (usually mutualistic) Example – E.coli. It gets a warm environment with free food; what do we get? Vitamin K, and protection from pathogens; since
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This note was uploaded on 04/07/2008 for the course BIO 315 taught by Professor Schmidt during the Spring '08 term at SUNY Stony Brook.

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bio 315 chapter 15 - Chapter 15: Infection and Disease Part...

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