LM16 - Microbes (Bacterial) making history and in the news...

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1 Microbes (Bacterial) making history and in the news Bubonic plague ( Yersinia pestis ) Anthrax ( Bacillus anthracis ) E. coli and Salmonella H. pylori
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2 Plague ( Yersinia pestis ) Claimed > 200 million deaths thruought history Bubonic form 50-75% mortality (spread by fleas) Pneumonic form > 90% mortality and highly contagious (person to person) 2003 -- still exists, >2000 cases worldwide (97 in US since 1990) Currently antibiotics successfully treat 90% of reported cases, but R plasmids now found in some infections
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Plague (Fig. 20.31) 3 Y. pestis causative agent -- G- rod, obligate parasite, 3 plasmids encode virulence factors Life cycle shown at left, reservoirs are primarily rodents in wild, in whom fleas find preferred host Wild rodents interact with domestic populations and fleas can hop onto new hosts (less preferred) When domestic hosts become scarce, fleas hop onto and feed off humans (but do not reproduce)
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Plague in the flea (Fig. 20.31) 4 In flea: At 26-28 0 , flea-specific virulence factors are made that plug flea’s digestive path from mouth to stomach, causing flea to starve and bite many hosts, spreading the pathogen Some scientists hypothesize that “little ice age” (around 1250-1850 AD) contributed to spread of plague, and the subsequent warm climatic conditions contribute dto its disappearance
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Plague pathogenesis in human host 2 stages of infection inside human (intra- and extra- cellular) Intracellular: Unencapsulated Y. pestis are initially engulfed by macrophages Y. pestis can grow intracellularly, travel to and spread within lymph nodes first, develop capsules Extracellular: bacteria with capsules lyse host cells, are released into blood and travel throughout the body, causing lung infection, sepsis
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Plague: Y. pestis virulence factors (Fig. 20.31) Capsule (F1 protein) only produced at 37 0 (not made in flea) Capsule inhibits phagocytosis by both PMNs and M Φ ; is adhesin for IL-1R on macrophges, allowing the microbe to bind to surface of APC Type III secretion system (includes V antigen), injects 6 proteins (apoptotic) into bound APC pla (plasminogen activator) is produced; this is a protease that inactivates complement Siderophores bind tightly to, and then transport iron into the pathogen Exotoxins, endotoxins fast growth all contribute to septicemia 6
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Treatments for plague Antibiotics successfully treat most cases of bubonic plague,
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This note was uploaded on 03/31/2010 for the course MCB 3020 taught by Professor Ogden during the Spring '08 term at University of Florida.

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LM16 - Microbes (Bacterial) making history and in the news...

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