Exam 3: Topic 15 Flashcards
Review the following organ systems that have resident microflora: human skin, oral cavity + gastrointestinal tract, respiratory tract, urogenital tract. Identify the particular organs or tissues that have resident microflora and those that should remain sterile.
• The closer you are to the oral or nasal cavity, the more microbes that organ or tissue will support. Oral cavity houses over 700 species. The bronchus and lungs should remain sterile
• Resident: oral cavity and pharynx contain resident microflora
• Transient: found in the esophagus and small intestine.
• Stomach should sterilize most food before it passes into the small intestine, some pass through alive
Review the following organ systems that have resident microflora: human skin, oral cavity + gastrointestinal tract, respiratory tract, urogenital tract. Identify the particular organs or tissues that have resident microflora and those that should remain sterile.
• The closer you are to the oral or nasal cavity, the more microbes that organ or tissue will support. Oral cavity houses over 700 species. The bronchus and lungs should remain sterile
• Resident: oral cavity and pharynx contain resident microflora
• Transient: found in the esophagus and small intestine.
• Stomach should sterilize most food before it passes into the small intestine, some pass through alive
What is the minimum infectious dose (MID)?
of microbes required to cause infection in 50% of susceptible hosts.
What factors influence the MID? How does this relate to disease transmission?
• Can vary by portal of entry, type of pathogen, or susceptible v immune.
• Lower MID = easier to transmit.
Define the following words: resident microflora, transient microflora, disease, infectious disease, pathogens, pathogenicity, opportunist, localized infection and systemic infection.
• Resident microflora:
○ permanent fixtures of community
• Transient microflora:
○ Temporary guests
• Disease:
○ harmful deviation from an organism’s normal state that’s caused by a microorganism, such as a virus, bacteria, fungus, or parasite
• Infectious disease:
○ disorder caused by a pathogen, which is a harmful microorganism that enters and multiplies in a host organism
• Pathogens:
○ a microorganism or other organism that causes disease in a host
• Pathogenicity:
○ ability of a microorganism to cause disease in a host
• Opportunist:
○ participate as a member of resident or transient microflora. True opportunists can cause infections if provided with the “right” opportunity.
• Localized infection:
○ an infection that is confined to a specific area of the body, such as an organ or body part
• Systemic infection:
○ spreads throughout the body’s systems, rather than being localized to a single organ or body part.
Describe a few “opportunities” that an opportunistic bacterium might seize to cause infection
• access to a sterile environment
• loss of protective microflora (potentially from antibiotics
immunocompromised
What is a virulence factor? Be sure to identify the various virulence factors for bacteria as it relates to the next objective
• Any structural or secreted piece of the microbe that enhances its ability to cause disease.
• Allows the pathogen to causes the diseases it causes.
• Ex: capsules increase pathogenicity; taking it away will not cause disease = virulence factor.
○ fimbriae
○ “toxin” = yes
○ flagella, help escape immune system
○ ability to metabolize sucrose = NO
○ Attachment = yes
BIG OBJECTIVE: Describe how bacteria can cause infectious disease. What are some portals of entry and how do they usually relate to the site of infection? Describe the importance and mechanism of colonization, and the role of toxins (including endotoxins and exotoxins) in actually causing disease.
• Portals of entry: reproductive tract, Nose/mouth, insect bite, blood (wound/incision), Mucous membranes of eyes.
• Attachment is necessary; attaching to a surface is considered colonizers; getting inside the cell is invasive bacteria.
○ it represents the initial step where bacteria establish themselves on a host’s tissue, allowing them to access nutrients, evade immune responses, and ultimately multiply to a level where they can produce harmful toxins or directly damage host cells, thus initiating the disease process
• Bacteria release toxins that contribute to disease symptoms/severity.
○ Exotoxin- purposefully secreted.
§ exotoxins are much more specific in their action and the cells they interact with. Each exotoxin targets specific receptors on specific cells and damages those cells through unique molecular mechanisms.
§ intracellular targeting (comprise two components: A for activity and B for binding. Thus, these types of toxins are known as A-B exotoxins. The B component is responsible for the cellular specificity of the toxin and mediates the initial attachment of the toxin to specific cell surface receptors. Once the A-B toxin binds to the host cell, it is brought into the cell by endocytosis and entrapped in a vacuole. The A and B subunits separate asthe vacuole acidifies. The A subunit then enters the cell cytoplasm and interferes with the specific internal cellular function that it targets); membrane disrupting; and superantigens.
§ help bacteria enter and survive in host cells and tissues
○ Endotoxin-LPS
§ During infection and disease, gram-negative bacterialpathogens release endotoxin either when the cell dies, resulting in the disintegration of the membrane, or when thebacterium undergoes binary fission. The lipid component of endotoxin, lipid A, is responsible for the toxic propertiesof the LPS molecule
§ lipid A triggers the immune system’s inflammatory response
○ Immune response to the large # of bacteria cause disease morbidity.
Briefly describe how viruses cause disease.
I. virus enters a cell
II. substance in the cell begin to strip off the viruses outer coat of protein.
III. the nucleic acid in the center of the virus is released
IV. the nucleic acid gets into the cells chemical manufacturing system
V. the cell ignores its own chemical needs and switches to making new viruses
the cell is sometimes destroyed in the process. Many of the new viruses are release to infect other cells.
List the four stages of disease. What is the incubation phase? At what stage are the symptoms unspecific and at which point are they severe? Can a person in the convalescent stage still transmit the disease?
• Incubation period:
○ between initial exposure and symptoms
• Prodromal stage
○ first onset of symptoms, may be nonspecific
• Period of invasion
○ full blown sickness
○ most infectious; number of pathogens are in their highest numbers.
• Convalescent period
○ recovery
Differentiate between the terms prevalence and incidence
• Incident rate:
○ A measure of how frequently a disease occurs in a population over a specific time period
○ # new cases per time / 100,000
• Prevalence rate:
○ the total number of existing cases of disease in a population at a specific time
○ # of existing cases right now / 100,000
Define the following terms: epidemic, endemic, pandemic
• Endemic:
○ geographically restricted to an area but low levels of disease always present.
• Epidemic:
○ rapid increase in incident rate
• Pandemic:
○ global epidemic
Describe a few common portals of exit.
blood, feces, urine, sputum/spit/sneeze, skin flakes, breast milk, secretion (mucous membrane, such as semen).
What is the difference between an animal reservoir and an animal vector?
• Animal reservoir: a non-human animal that is infected with a pathogen and can long-term host the disease it causes
Animal vector: a living organism that transmits a disease-causing agent from an infected animal to another animal or to humans
Name a bacterium, virus, and prion agent that is found in an animal reservoir.
• Virus: ebola virus (in bats) or rabies (in dogs)
• Bacterium: E. Coli
• Prion: BSE (mad cow disease)
