Host Microbe Interactions

Host Microbe Interactions - Host Microbe Interactions Kathy...

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Host Microbe Interactions Kathy Huschle Northland Community and Technical College Host Microbe Interactions daily we ingest thousands of microorganisms on the food we eat inhale hundreds of thousands of microorganisms in the air we breath have microorganisms stick to us wherever we go most of these invaders have no ill effect on us as we slough, cough, gag, urinate and defecate them away we are also protected by the “friendly” resident microorganisms found throughout our body microorganisms very easily colonize the warm, moist, nutrient rich environment we call the human body usually they live as normal flora in some cases, they are able to overcome the bodies defenses, and cause disease organisms that can cause any noticeable damage, invade tissue, or produce toxins are called pathogens please review the terms used for the study of infectious disease found in Table 19.1 on page 460 in your text Anatomical Barriers in addition to providing barriers to the microbial world, skin and mucous membranes also create an environment for interacting microorganisms and the human body these interactions are referred to as symbiosis, which means living together the players in symbiosis are referred to as symbionts symbiotic relationships between microorganisms and a host include mutualism
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commensalism parasitism Mutualism in this type of relationship, both partners benefit E. coli synthesizes vitamin K in the intestine in exchange the large intestine provides nutrients necessary for survival of the microorganisms Commensalism one organism is benefited and the other is unaffected by this type of relationship many of the microorganisms that make up our normal flora inhabit places like the eyes, ears, and external genitalia these bacteria live on secretions and sloughed off cells they bring no benefit to the host and yet the microorganisms benefit greatly from the environment they inhabit Parasitism one organism benefits at the expense of the other all pathogens are parasites Normal Flora microorganisms that colonize a host without causing disease two types of normal flora exist resident flora are microorganisms that inhabit sites on the body for extended periods transient flora are microorganisms that are temporary the presence of normal flora cover potential adherence sites for invading microorganisms consume the available nutrients produce compounds toxic to other microorganisms
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when the balance between normal flora and pathogens is upset, disease can result the normal bacterial microorganisms of the adult human vagina maintain the pH at about 3.4 – 4.5 the presence of this normal flora inhibits the overgrowth of Candida albicans , yeast if the presence of the normal flora is eliminated by antibiotics, or excessive douching, the pH of the vagina becomes nearly neutral, creating an environment very conducive to the growth of C. albicans
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