Chapter 11- Interactions Between Microbes And Humans Flashcards
Where do we find normal biota?
Skin and it’s adjacent mucous membranes, respiratory tract, gastrointestinal tract, outer opening of urethra, external genitalia, vagina, external ear canal, external eye.
How do we initially become colonized with normal biota?
Breaking of the fetal membranes, at which time microbes from the mothers vagina can enter the womb.
Babies born by cesarean section typically are colonized by adult skin biota.
How is colonization of the large intestines established?
Depending on how the baby is fed, either by bottle or by breast.
Define microbial antagonism.
A relationship in which micro organisms compete for survival in a common environment by taking actions that inhibit or destroy another organism.
Describe bacteriocins
Proteins produced by certain bacteria that are lethal against closely related bacteria and are narrow spectrum compared with antibiotics; these proteins are coded and transferred in plasmids.
Define opportunistic pathogens.
In infection, ordinarily nonpathogenic where weakly pathogenic microbes that cause disease primarily in and immunological compromised host.
Define infectious disease.
The state of damage or toxicity in the body caused by an infectious agent.
What pre-disposing factors can make an individual more likely to contract a disease?
Old age and extreme youth, genetic defects and immunity, and acquired defects in immunity, surgery and organ transplants, underlining diseases such as cancer, liver malfunction, diabetes, and chemotherapy or immunosuppressive drugs, physical and mental stress, pregnancy, and other infections.
List Koch’s postulates.
- Find evidence of a particular microbe in every case of disease.
- Isolate that microbe from an infected subject and cultivated and pure culture in the laboratory; perform for microscopic and biological characterization.
- Inoculate a susceptible healthy subject with the laboratory Isolette and observe the same resultant disease.
- Re-isolate the same agent from this subject.
Define pathogen.
Any agent, usually a virus, bacteria, fungus, protozoan, or helminth, that causes disease.
Define pathogenicity
The capacity of microbes to cause disease.
Define virulence
In infection, the relative capacity of a pathogen to invade and harm host cells.
Define virulence factor.
A microbes structures or capabilities that allow it to establish itself and a host and cause damage.
Define etiology.
The study that deals with causes of disease. It is the classification of disease.
What factors play a role in the progression of infection?
Pathogenicity, true pathogens, opportunistic pathogens, virulence of a microbe and the virulence factor.
What is the difference between an Endogenous and An exogenous pathogen?
Endogenous- originating or produced within an organism or one of its parts.
Exogenous- originating outside of the body.
What is meant by portal of entry? Give examples.
Portal of entry is the route of entry for an infectious agent; typically a cutaneous or membranous route such as the skin, gastrointestinal tract, respiratory tract, urogenital tract.
What is the most common portal of entry?
Mucous membranes are the most common – respiratory gastrointestinal and Genitourinary tracts
Define infectious dose
Minimum number of microbes to cause infection
Define ID 50
Infectious dose for 50% of the test population
Define LD50
Lethal dose, of a toxin, for 50% of the test population.
The ID 50 of bacteria A is 100 cells and that ID 50 of bacteria B is 200 cell. Which bacteria or more virulent?
Bacteria B.
The LD50 of toxin A is 2 MG/KG and toxin B is 200 MG/KG. Which toxin is more potent?
Toxin A
What types of microbes make up our normal or resident biota?
Bacteria, fungi, Protozoa, viruses and arthropods.
