Exam 1 Study Deck Flashcards
how does a light microscope work and what is it used for
uses light and a magnifying lens to view small objects
how does a digital microscope work
uses optics and a digital camera to output an image to a monitor
how does a fluorescence microscope work
uses fluorescence to generate an image
used in conjunction with a flourescently stained organism which will produce a color when exposed to a wavelength of light
how does a phase contrast microscope work
light is shone through a transparent specimen
phase shifts are converted to brightness changes in the image
how does a dark field microscope work
light it shone at a specimen and produces a dark area around the specimen
this darkness occurs because there is nothing in those areas to scatter the beam of light
how does an electron microscope work
uses a beam of accelerated electrons as a source of illumination
what are the some phenotypic ways to classify an organism
size
shape
hemolysis
texture
rate of growth
color
odor
what is the difference between genotype and phenotype
genotype: unique, genetic DNA
phenotype: observable expression (ex. size)
what are the two modes of transmission of diseases
direct and indirect
what are 5 examples of direct transmission of disease
1.) direct contact
2.) droplet infection
3.) contact with soil
4.) inoculation into skin or mucosa (vaccines)
5.) transplancental (vertical)
what are 5 examples of indirect transmission of disease
1.) vehicle (water, food, air, and medical devices)
2.) vector (animals, insects, and other humans)
3.) air
4.) fomite (objects likely to carry infection like furniture)
5.) unclean hands and fingers
what are the two intervening agents for modes of transmission
vectors and vehicles
what makes up the specific immune response
memory through previous exposures (vaccines)
how does the ingestion and removal process of invaders work
phagocytes ingest the bacteria by endocytosis
they engulf in phagosomes which then fuse with lysosomes
toxic chemicals in the lysosomes destroy the invaders
which antibody is the most abundant antibody produced
IgG
which antibody is the largest in size and is the initial antibody produced in reaction to an infection
IgM
which antibody is found in various body fluids
IgA
which antibody is secreted in parasitic infections and during allergies
IgE
which antibody is attached to the surface of specific immune system cells and is involved in the regulation of antibody production
IgG
generally, how does antibody-mediated immunity work
B-cells are stimulated by helper T-cells to become plasma cells and memory B-cells
plasma cells make antibodies
generally, how does cell-mediated immunity work
helper T-cells stimulate cytotoxic T cells
memory T-cells are created
what are virulence factors
characteristics of organisms allow them to cause disease in humans
what are the 5 main virulence factors
1.) ability to attach
2.) ability to invade
3.) ability to survive inflammation
4.) ability to survive against the immune system
5.) production of microbial toxins
what are the three methods of accomplishing diversity in bacteria
1.) mutation
2.) genetic recombination
3.) gene exchange
what is a mutation
a change in the original nucleotide sequence of a gene within an organism’s genome
what is genetic recombination
pieces of DNA that are homologous (similar) are exchanged
what are the three types of gene exchange
1.) transduction
2.) transformation
3.) conjugation
what is transduction
DNA from a virus is packaged in a bacteriophage
bacteriophage then infects bacterial cell
what is transformation
donor cell lyses to release DNA
DNA is then uptaken and exchanged with other pieces of DNA
what is conjugation
chromosomal or plasmid transfer of DNA by an intracellular bridge
what is differential media
media that allows you to differentiate between organisms based on what is added to the media
what is selective media
media that is selective for only certain types of media (will kill all other types of organisms)
what is MacConkey agar selective for
gram negative rods
what is MacConkey agar differential for
lactose fermenters and bile positive organisms
what is 5% Sheep Blood Agar differential for
hemolysis (beta, gamma, and alpha)
what is CNA agar selective for
gram positive cocci and rods
what is CNA agar differential for
hemolysis (beta, gamma, and alpha)
what two things does CNA agar contain to suppress Gram negative organisms
colistin and nalidixic acid
chocolate agar best grows what
fastidious bacteria like Hemophilus and Neisseria
what is chromogenic media used for
used to select and differentiate bacteria by color
what is the single most important phenotypic identifying characteristic used to identify organisms
the gram stain
what is the main difference between gram positive and negative organisms
gram positive: thick peptidoglycan layer covering a cytoplasmic membrane - no outer later
gram negative: cytoplasmic membrane covered by a thin peptidoglycan layer covered with a thick lipopolysaccharide layer
what are the 5 steps to a gram stain
fixation
crystal violet - purple dye
iodine treatment - forms a complex between the violet and iodine
decolorization - thins out the peptidoglycan layer, gram negative lose their color
counter stain (safranin) - stains red/pink
what happens during the decolorization step of the gram stain
alcohol strips the gram negative bacteria of their outer wall and washes away the violet and iodine - leaving them colorless
gram positive bacteria are unaffected due to their thick peptidoglycan layer and lack of outer cell wall
what happens during the counter stain step of the gram stain
colorless gram negative organisms now stain pink and gram positive organisms stay purple
what does MALDI-TOF stand for
matrix-assisted laser desorption ionization time of flight mass spectrometry
explain the steps of the MALDI-TOF
1.) colony is applied to a stainless steel plate and allowed to dry
2.) chemical matrix is added and allowed to dry
3.) plate is placed in the instrument and a laser is applied
4.) matrix absorbs the energy transferring heat to proteins in the sample
5.) soft ionization causes ions to float up a vacuum tube based on their size and charge
6.) a spectrophotometer measures the ions and protein charges to mass ratio and creates a graph unique to the organism
what are some of the benefits of the MALDI-TOF method
-measures microbial proteins so it provides a more reliable means of discriminating one species from another
-good for differentiating organisms with complex nutritional requirements
-it’s very quick which allows patients to get treated more quickly
-expensive to purchase at first but saves money in the long run
-faster to get diagnosis of things like yeasts and anaerobes
what are the three types of bacterial resistance
intrinsic (inherent)
aquisitional
mutational
what is intrinsic resistance
organism is inherently not susceptible to the antibiotic
what is aquisitional resistance
organism codes for certain proteins that make it resistant to an antibiotic
what is mutational resistance
organisms can get resistant mutant genes through normal bacterial genetic exchange, thus making them resistant to an antibiotic
what are the 5 general mechanisms of antibiotic resistance
1.) decreased cell permeability
2.) active efflux
3.) enzymatic inactivation of the antibiotic
4.) altered target (modification of drug receptor site)
5.) synthesis of a resistant metabolic category
how do plasmids play a role in antibiotic resistance
the plasmid is a small, circular piece of DNA
these plasmids can contain antibiotic resistant genes these genes can be transferred through conjugation, transduction, or transformation
this allows bacterial to share antibiotic genes with their neighbors - thus making them harder to kill
what are the three main key elements of host vs microbe interactions
relationship, physical encounter between the two, compromise
what is the relationship like between a host and microbe
extremely complex
most situations are mutually beneficial but can vary
what is the physical encounter like between host and microorganism
microorganisms colonize on the host’s surface where they can enter, invade, and spread
what are the three types of compromises that can create favorable conditions for the development of disease between a microbe and its host
normal flora disruptions
reduced immunity
introduction into host via injury
what is an opportunistic pathogen
one that does not normally cause harm unless something specific happens to the host (trauma)
what is the definition of antibiotic
means “against life”
substance produced by a microorganism or by chemical synthesis which inhibits the growth of or kills microorganisms
what are some desired characteristics in an antibiotic
toxic against pathogen but not host
high LD50
low MIC and MBC
bacterial
broad or narrow spectrum depending on infection
lack of side effects
ability to cross outer and cytoplasmic membranes
resistant to inactivation by microbial enzymes
what is LD50
lethal dose 50% - dose of an antibiotic to kill 50% of the microorganisms
what is minimal inhibitory concentration (MIC)
measure of the concentration of the minimum antibiotic necessary to inhibit growth of pathogen
what is minimal bactericidal concentration (MBC)
measure of the concentration of the minimum antibiotic necessary to kill the target pathogen
what are the two main types of presentations of infections
acute vs chronic
