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CHAPTER 14 Microbiology

CHAPTER 14 Microbiology - PATHOGEN the scientific study of...

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PATHOGEN: – the scientific study of disease o Concerned with: 1st. ETIOLOGY: cause of disease 2nd. PATHOGENESIS: the manner in which a disease develops 3rd. structural and functional changes brought about by disease and their final effects on the body INFECTION: colonization of the body by pathogens o infection may exist in the absence of disease DISEASE: an abnormal state in which the body is not functioning normally o occurs when infection changes state of body NORMAL FLORA(microbiota): microorganisms that establish more or less permanent residence (colonizes) but that do not produce disease under normal conditions TRANSIENT FLORA (microbiota): may be present for several days or months and disappear OPPORTUNISTIC PATHOGEN: Under proper conditions mutualistic organisms may be come pathogens o EX: e.coli not harmful in large intestine, but harmful to other parts of body Like if in Urinary bladder – cystitis; Or in CSF - meningitis MICROBIAL ANTAGONISM: competition between microbes o normal microbiota can benefit the host by preventing the overgrowth of harmful microorganisms, protect the host by: o occupying niches that pathogens might occupy (competition for nutrients and space) o producing acids (harmful to invaders) o changing oxygen level of immediate environment o producing bacteriocins o Examples Vagina · Normal flora maintain pH of 3.5 – 4.5; use of antiobitoics and excessive douching raises PH · Inhibits growth of Candida albicans (because overgrowth causes vaginitus, yeast) Mouth · Streptococci produce compounds that prevent growth of g+ and g- cocci Large intestine · E. coli produce bacterocins, proteins inhibit growth of other bacteria · Inhibits Shigella and Salmonella Large intestine · Intestinal microbiota normally inhibit cl. Difficule and prevent it from attaching but antibiotics can eliminate normal microbiotic · Gastrointestinal problems following antibiotics: Mild diarrhea, colitis, fatal toxemia ***PROBIOTICS: live microbes applied to or ingested into the body intended to exert a beneficial effect (ex: lactobacillis acidophilis) SYMBIOSIS: a relationship between normal microbiota and the host, where at least one organism depends on another o 3 types: COMMENSALISM: one organism benefits and the other is unaffected · Examples: many normal microbiotia, like corynebacteria on eye; saprophytic bacteria in ear (both of these live on secretions and sloughed off cells and bring no apparent benefit or harm to host) MUTUALISM: benefits both organisms · Examples: E. Coli in large intestine: Synthesize B and K vitamins (host benefits); Supply nutrients to normal flora (flora benefits) PARASITISM: One organism benefits and the other is harmed · Examples: (tapeworm, bacteria, etc) KOCH’S POSTULATES:
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**KOCH: German physician, Late 1800’s, Worked with anthrax, Developed a framework for studying the etiology of infectious diseases o SUMMARY: 1.the same pathogen must be present in every case of the disease 2. the pathogen must be isolated from the disease host and grown in a pure culture
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