Week 5 Notes
Week 5 Notes HTH 245
Popular in Foundations of Infectious Disease
Popular in Health Sciences
This 6 page Class Notes was uploaded by Katlyn Palka on Sunday October 2, 2016. The Class Notes belongs to HTH 245 at James Madison University taught by in Fall 2016. Since its upload, it has received 5 views. For similar materials see Foundations of Infectious Disease in Health Sciences at James Madison University.
Reviews for Week 5 Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/02/16
Chapter 7: Concepts of Microbial Disease ● Symbiosis: describes an association between two or more species with three possibilities: ○ Mutualism: ■ Both members of the association enjoy benefits ■ Ex: the association between termites and protozoans (pg. 153) ○ Parasitism: ■ An association in which a parasite (microbe) lives at the expense of the host (the human) ● Parasite: all microbes, worms, viruses that produce disease ○ Commensalism: ■ The relationship between two or more species in which one benefits and the other is indifferent (neither benefited nor harmed) ○ These three possibilities aren’t cut and dry, there are blurred lines and grey areas between the three of them ○ The seesaw relationship between mutualism, commensalism, and parasitism ■ For mutualism and commensalism when there are nonpathogens there is balance between the two. The nonpathogens don’t cause any harm ■ For parasitism the nonpathogens that normally wouldn’t cause any harm become opportunists ● When you already have a depressed immune system the nonpathogens become pathogens which can cause the risk of disease to become higher ● Example: HIV ● Microbes as agents of disease ○ Miasmas ■ Were thought to be the cause of disease ■ People thought that bad air was the cause of disease and death ○ In the early 1800s there was a link made between lack of sanitation and disease ■ This is the beginning of germ theory ● Koch’s postulates (the steps to prove a particular agent causes an illness based on bacteria) ○ 1. Association ■ The causative agent must be present in every case of a specific disease ■ Every person that has the disease must test positive for that agent that you propose is causing the disease ○ 2. Isolation ■ The causative agent must be isolated in every case of the disease and grown in pure culture ■ Take the microbes out of the infected person and culture them ○ 3. Causation ■ The causative agent in the pure culture must cause the disease when inoculated into a healthy and susceptible laboratory animal ■ Take the thing you took out of the diseased people and put it in a healthy species and it should get sick ○ 4. Reisolation ■ The causative agent must be reisolated from the laboratory animal and be identical to the original causative agent ■ Take it out again and make sure it was the same microbe you put in the species in the first place ● Microbial mechanisms of disease ○ Infection: ■ When you have the microbe in you and it’s multiplying, but you don’t have any symptoms ● Asymptomatic or subclinical ○ Disease: ■ When you start to show symptoms ○ The chance of acquiring an infection depends on 3 factors ■ Dose (n) ● The number of microbes that are encountered ■ Virulence (V) ● Virulence factors ■ Resistance (R) ● Host immunity ■ There is a formula that determines the severity of an infection and can tell whether or not a person will end up getting a disease from the infection ● D=nV/R ● D is the severity of the infectious disease ● Pathogenicity and Virulence ○ There is an infective dose (ID), which is the minimal dose that is necessary to establish an infection in the host ■ More virulent organisms have a smaller ID than less virulent organisms ● It takes less microbes to make you sick (more virulence) ○ It doesn’t need as many copies of itself to make you sick ○ LD❑ 50is the 50% lethal dose ■ It is a laboratory measurement of virulence that is determined by injecting animals with varying concentrations of microbes and the dose that kills 50% of the animals in an established time ○ Pathogenicity: the ability to cause disease ○ Virulence: a measure of pathogenicity ■ Encompasses two types of virulence factors that enable pathogens to overcome host defense mechanisms and to multiply and cause damage ● Defensive strategies (4) ○ They allow microbes to escape destruction by the host immune system ■ Bacter ial adhesins ● A dhere to receptor molecules at port of entry ■ Capsu les, M protein, Waxy cell wall ● I nterferes with phagocytosis, multiplies inside immune cells ■ Antige nic variation ● C hanges surface antigens to avoid detection by antibodies ■ Enzym e secretion ● A llows it to survive in harsh environments ● Offensive strategies (3) ○ They result in damage to the host ■ Exoen zymes ● H elp to spread bacteria by causing damage to host cells ■ Exoto xins ● P roteins synthesized by the microbe and secreted into the host’s tissues (only in gram positive) ■ Endot oxins ● T hey are structural components of outer membrane of gram negative cells. Called lipopolysaccharides ● T hey are not usually released during microbial growth and metabolism ● Virulence mechanisms of viruses ○ Defensive side: ■ Since they are obligate intracellular parasites (they depend on the their host cells for survival and replication) which allows them to go through antigenic variation ● They can change their antigen coats which hide from components of the immunes system ● Example: influenza virus ○ Offensive side: ■ Consists of death (lysis) of the host cell from: ● Production of large numbers of replicating viruses ● Inhibiting host protein synthesis ● Damage to plasma membrane ● Inhibiting host cell metabolism ● Stages of microbial disease ○ Incubation ■ The time between the pathogen’s access to the body and the display of signs and symptoms ● No symptoms are shown in this stage ● The infected individual is contagious here ● This stage can vary in time ○ Staph food poisoning (24 hours) ○ HIV (6 months to 12 years) ○ Prodromal ■ A short stage ■ The symptoms are vague and mild ● Frequently characterized by tiredness, headache, muscle aches ■ The infected individual may be contagious depending on the infection ○ Illness ■ The disease is acute ■ Most severe stage ■ It is accompanied by typical symptoms ● Fever, nausea, vomiting, chills, headache, muscle pain, fatigue, swollen lymph glands, and rash ■ In this stage either you recover or you die ● Results in either recovery or impairment or death of the host ○ Decline ■ The immune system won the battle ■ The signs and symptoms start to disappear ■ You start to feel better ○ Convalescence ■ This is the recovery stage ■ There is repair of damaged tissues and strength is regained ■ In some cases a person can become a chronic carrier ● Sometimes with cholera and typhoid fever, but this is where the disease stays in you forever, but you aren’t sick and you show no symptoms Class Notes 9/28 ● Video: ○ Miasma: bad air (floating in specific regions) ■ They thought it could be treated with good smells in the air (flowers, incense) ■ The beak would hold the incense and herbs that could beat miasma ● Video: how a few scientists transformed the way we think about disease ○ Cholera outbreaks led to the discovery of microbes ■ Spread through infected water ■ He mapped the city and shut down a water pump ■ Childs dirty diapers were thrown into a waste section which then contaminated the water ○ Germ theory: microbes were found using early microbes ● Video: Flu vaccine ○ Viruses are always changing ○ The antibodies become out of date and can’t protect from the influenza each year ○ Attach to the Ha protein and block it and prevent it from spreading ○ When the influenza enters cells and when it replicates it can change a little bit and eventually the immune system can’t recognize the antigens anymore that is why we need a new flu vaccine ○ They predict the type of flu that will circulate each year and that is the flu vaccine that they create each year ○ Has a low uptake: low amount of people that get the flu vaccine
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'