Lab Midterm (Ex 1-7) Flashcards
___ diseases are transmitted person to person.
Contagious (or communicable)
Transmission may be made through contact with contaminated inanimate objects, called ____, such as bedding, towels, drinking vessels, or needles.
Fomites
Some diseases are transmitted by insect and arthropod ___.
Vectors
This type of transmission occurs when an insect carries fecal pathogens on its feet, and then walks on food.
Mechanical transmission
This type of transmission occurs through the bite of an infected mosquito, tick, or flea.
Biological transmission
What is an example of a disease that is non-communicable and cannot be passed from one infected person to another? How is this acquired?
Anthrax. It is acquired only from infection from spores from the environment.
This is the study of patterns of disease infection and spread.
Epidemiology
These are present in a population all the time at low levels
Endemic diseases
These affects many individuals in a population in a short time.
Epidemic diseases
These are worldwide epidemics.
Pandemics
These are diseases that can spread from animals to humans.
Zoonoses
___ are humans or animals that are sources of infection.
Reservoirs
Human reservoirs that are infected without having any symptoms are called _____.
Disease carriers
If you were an epidemiologist, tracing the source of an epidemic, you would trace it back to it’s original source case, which is also known as ___.
index case
What part of the microscope allows you to control the amount of light that passes through your slide?
Diaphragm
Which lenses do we use in the microbiology lab?
10x and 100x (oil immersion lens)
In addition to these lenses, where else do you get additional magnification, and how much magnification is it?
The eyepiece contains a 10x lens.
How do you determine the total magnification with your microscope?
Multiply the lens magnification power and the eyepiece lens magnification power.
What is a stain that differentiates between two types of bacteria, and also helps to visualize the bacteria?
A differential stain
What two classes does Gram staining differentiate between? What structure allows this to be visualized in a Gram stain?
Gram positive and Gram negative.
The peptidoglycan in the cell wall structure is what causes this to be visualized.
What is the primary dye used in a Gram stain?
Crystal Violet
What is the counter stain used in a Gram stain?
Safranin
What is name of the mordant that is used after the primary dye?
Gram’s Iodine
How does the mordant act on the primary dye in a Gram stain?
It crystalizes the dye that penetrated into the microbe cell wall, locking it in place
Which cells have a larger, more highly cross linked peptidoglycan layer? What color will they appear?
Gram positive. Purple
What color do Gram negative cells appear in a Gram stain?
Pink/red
How long should the mordant be left on the slide before rinsing?
1 minute
When should you heat fix the slide?
After the sample has dried onto the slide, before starting the Gram stain.
How long should the primary dye be left on the slide before rinsing?
45 seconds
What are the next 3 steps that should be taken after letting the mordant sit on the slide?
- Rinse with water for 5 seconds.
- Decolorize with ethanol.
- Rinse again with water.
How much ethanol should be used to decolorize the slide?
Approximately 10-15 drops
How long should the counter stain be left on the slide before rinsing?
1 minute
When are spores produced?
When environmental conditions are poor (essential nutrients/water is not available to the cell)
How are spores reproduced?
Spores are not formed by reproduction. One spore is generated from one mother cell.
What is the first step in spore staining, before you ever actually begin staining?
Prepare a heat fixed slide of the sample.
What is the first stain used in a spore stain?
Malachite green
What do you do after flooding the initial stain in a spore stain?
Place the slide on a staining rack. Hold the bunsen burner over the stain just into it starts steaming.
What do you do when the stain begins to evaporate during the steaming process in the spore staining?
Do not let it evaporate. Keep applying stain as needed.
How long does the stain need to sit/steam on a spore stain?
5 minutes
What should you do before rinsing the steamed stain off this slide?
Allow the slide to cool so the slide doesn’t break.
After rinsing the slide, what is the next stain used in spore staining? How long should it sit on the stain?
Safranin. 1 minute.
Growth medium may be chemically defined or may contain ___ ___ ___, or even more complex substances such as ___ ___ ___ ___.
partially digested proteins (peptones)
bovine red blood cells
What is extracted from marine red algae?
agar
What is added to growth medium to make it solid?
agar
What is the common agar used in the lab?
nutrient agar
How is medium sterilized before use?
Autoclave (121’C at 15 PSI for 15 minutes)
How would you prepare the TSA plate to do an environmental sample (such as the bottom of your shoe)?
Lawn
What is the method for transferring cultures from from one medium to another without contamination?
Aseptic technique
What plating method would you use for a mixed culture?
Streak plate
When do you flame the loop when doing a streak plate?
Before inoculating the loop, and again before each sector on the plate
How do you tell whether there is growth in nutrient broth?
Turbidity
Why are petri plates inverted in the incubator?
To prevent water evaporation droplets from falling onto the plate surface.
What does CFU stand for?
Colony forming units
What is the technique called that is often used to determine the number of bacteria in a sample?
Standard plate count
What technique needs to be done to insure that you have an adequate number of sample to count when determining CFU?
Serial dilution
CFU/ml = ?
Colonies counted / (0.1 ml)(the dilution)
How do you calculate the dilution?
(0.01)(0.01)(0.1)(0.1)
as appropriate based on which plate presented the best for counting
What general type of media may inhibit/allow growth of certain bacterial species?
Selective media
What general type of media may present colonies in different colors based on certain characteristics?
Differential media
What does MacConkey Agar plates identify?
Lactose fermenting, Gram-negative enteric organisms
What do MacConkey Agar plates inhibit?
Growth of Gram-positive organisms
What color change happens with MacConkey Agar plates, and what does it signify?
Red. The bacterial colonies are fermenting lactose.
What causes the color change on the MacConkey Agar plates?
pH response due to the acidic environment from the fermenting lactose
What is a common medium used for the isolation of some pathogenic Gram-positive organisms, by measuring salt tolerance?
Mannitol Salt Agar (MSA)
What color change happens with MSA plates, and what does it signify?
Changes pH indicator from red to yellow. Ferments the Mannitol into acid.
What does growth/inhibition of growth signify on the MSA plates?
Growth demonstrates salt tolerance of Gram-positive organisms, while inhibition of growth shows salt’s inhibition of other organisms.
These grow only in the total absence of oxygen
Obligate anaerobes
These prefer higher concentrations of CO2 (5-10%)
Capnophillic organisms
These grow only in the presence of oxygen
Obligate aerobes
These require low oxygen concentrations (2-10%) for growth. Higher O2 concentrations will inhibit their growth and they also cannot grow in total absence of oxygen.
Microaerophiles
These can grow with or without oxygen (but usually grow better in the presence of oxygen).
Facultative anaerobes
What does growth in the solid medium tubes signify, in regards to oxygen requirements of organisms?
Oxygen gradient, high O2 to low O2 (top to bottom)
Where would you likely find obligate anaerobes in a tube of solid medium?
At the bottom
Where would you likely find facultative anaerobes in a tube of solid medium?
Scattered throughout, with more on top
Where would you likely find obligate aerobes in a tube of solid medium?
At the top
Where would you likely find microaerophiles in a tube of solid medium?
Somewhere in the middle
Which organisms prefer growth temps in the 15’C-20’C range?
Psycrophiles
Which organisms prefer growth temps in the 50’C-60’C range?
Thermophiles
Which organisms prefer growth temps in the 30’C-37’C range?
Mesophiles
What organisms might you find in the bottom of the ocean?
Psycrophiles
Which organisms are happiest to harm humans?
Mesophiles
Which organisms might you find in the Yellowstone hot springs?
Thermophiles
What type of bacteria are salt hating?
Halophilic
What type of bacteria are salt loving?
Halotolerant
When a solute concentration is greater outside of the cell, the solution is said to be ___.
hypertonic
When UV light exposure damages DNA, it is possible for structural changes to reverse with exposure to visible light. What is this known as? (2 answers)
Light Repair, or photo reactivation
Another mechanism to repair structural changes when visible light is not possible is known as _____.
Dark repair
How does the UV structural damage repair mechanism work (method when no visible light present)?
Involves enzymes which physically remove and replace the structural changes caused by the radiant energy
Flaming inoculation loops are an example of what type of sterilization technique?
Dry heat
This type of sterilization technique uses steam to sterilize.
Moist heat
What are 3 examples of sterilization techniques that use moist heat?
Boiling, autoclaving, pasteurization
What are the temp/time methods for pasteurization? (2 answers)
63’C (30 minutes) or 72’C (15 minutes)
What is the name for chemicals that are used on the surface of inanimate objects to kill microbes?
Disinfectants
True/False: There are chemicals that can single handedly completely kill all of the microbes in the area where it is applied.
False. There are none that can do that.
These are chemicals that are used on living tissues to kill microbes.
Antiseptics
An example of a common household antiseptic is ___.
Mouthwash
An example of a common household disinfectant is ___.
Bleach
Antibiotics are chemicals that are often produced by _____ (such as ____), and are used as a defense mechanism.
Microorganisms, such as fungi.
In human and animal care, antibiotics against pathogenic bacteria are either derived from ____ or are ____ ____.
Microorganisms; Synthetically produced
In general, how do antibiotics work to kill bacteria?
Each antibiotic works by a specific mechanism that targets some vital process of the specific bacteria to cause its death.
What method is used to determine the effectiveness of antibiotics on certain bacteria?
Disk-diffusion method
The effectiveness of an antibiotic on a bacterium is determined by evaluating the ________ (or the circle around the disk where the antibiotic noticeably affected the cell viability).
Zone of inhibition
What are the 3 classifications of an antibiotic, relative to the effectiveness of an antibiotic?
Resistant, Intermediate, Susceptible
What is the name for infections acquired in a hospital setting?
Nosocomial infections
What type of medium is used for antibiotic susceptibility testing?
Mueller-Hinton Agar (MH)
What is TSA?
Tryptic Soy Agar (plates)
How do you use forceps aseptically?
Dip forceps in alcohol, run through flame, let flame extinguish itself, let it cool
What type of plate do you use in the dilution plating, and what is the spread method for the plate itself?
TSA plate; Glass hockey stick spread evenly over entire plate
What type of media is best for when you need to dilute the bacteria?
Liquid media
What type of plate is best used for a streak plate?
TSA plate
What is BHI, and what is a characteristic of it?
Brain Heart Infusion (agar); It is very nutrient rich, great for festidious organisms
In a temperature comparison study, how do you determine which temperature an organism is most “happy”?
It is the most pigmented at that temperature
True/False: Salt-tolerant organisms can ferment mannitol
False. Salt-tolerant organisms CANNOT ferment mannitol.
What color is a MSA plate before used in an experiment?
Reddish
After spore staining a slide, how will a happy cell appear?
pink
After spore staining, what are you looking at when you see teal/bluish-green free cells floating in your slide?
Free spores
After spore staining, what are you looking at when you see pink cells, that have smaller teal/bluish-green cells inside of them?
These are spores in process, within the cell
