PMI 126 - Lecture 2

PMI 126 - Lecture 2 - Major Groups of Human Pathogens 1...

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Major Groups of Human Pathogens: 1. Viruses : - example: Polio, smallpox, influenza, measles, AIDS - obligate intracellular pathogen: only way viruses can grow is to get inside the living cells * the way they get in => to find a receptor on the living host cells * they carry nothing but their own genome and having a coat outside * once they get into the cell: 1. un-coat = naked genome (piece of DNA or RNA) in the cytoplasm 2. naked viral genome takes over the cellular machinery => replicate viral genome 3. syntheses the required proteins for building the coat 4. assemble 5. viruses escape the host cells by: 1. fusing with the host membrane 2. budding out * or the cell lyses and the newly form virus are released ** pathogen can exist either intracellular or extracellular in our body * viruses have two phases ; extracellular phase and intracellular phase some viruses learn how to convince the adjacent healthy cell to fuse with the infected host cell that have the virus replicating inside. Thus, virus can infect the healthy cell without being at the extracellular phase * certain (selective) antibodies are called neutralisin neutralize the viruses and/or its toxins by binding to it. and blocking the viruses from binding to the receptor of host cells = no replication * some antibodies can bind to the structures of virus that are shared by multiple micros. ex. vaccine of cowbox against smallpox (cross-reaction) * retrovirus : RNA viruses that are capable of inserting their RNA genome with carried enzyme reverse transcriptase to produce DNA from its RNA genome. - example of virus: ROTAVIRUS ; infant diarrhea * have 10 unique piece of double stranded RNA * h ave multiple different strain of virus which can exchange segments * i ndividual vesicles are exactly the same with exact 10 double stranded RNA * need all 10 to infect the host cell - example of virus: POLIO; infantile paralysis * once this virus enters the central nervous system via blood stream, preferentially infecting and destroying motor neurons, leading to muscle weakness and acute flaccid paralysis. 2. Bacteria - all of different growing requirement; some are obligate pathogens - example: Tuberculosis, tetanus, whooping cough - example: PSEUDOMONAS (soil bacteria) * associated this bacteria with opportunistic infections
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* particularly in patients with severe burns and in cancer and AIDS patients who are immunosuppressed . - example of bacteria: tuberculosis * about 1/3 of the world's population is thought to be infected with Mycobacterium tuberculosis, the causative agent of TB * TB kills more people worldwide than any other disease caused by a single bacterial pathogen (2 million per year die by TB) * only a small proportion (10%) of those who are infected with M. tuberculosis develop
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