Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
77 Cards in this Set
- Front
- Back
|
What does aseptic technique ensure? |
It insures that no contaminating organisms are introduced into culture materials when the latter are inoculated or handled in some manner; also insures that the bacteria does not contaminate the handler or others present |
|
|
Aseptic techniques can be used in what transfers? |
The transfer of a broth culture to a plate for streaking, or inoculating an isolated colony from a plate onto a slant culture to prepare a stock culture. |
|
|
What is the paramount importance in the identification process? |
Ensuring that only the desired organism is transferred in each inoculation is of paramount importance in the identification process. |
|
|
Why is the work area disinfected? |
To kill any microorganisms that may be present. This process will destroy vegetative cells and viruses but may not destroy endospores. |
|
|
How is the transfer of cultures achieved? |
By inoculating loops and needles |
|
|
How is a loop or needle sterilized? |
By inserting it into a Bunsen burner until it is red hot |
|
|
Why does a loop need to be sterilized? |
It will incinerate any contaminating organisms that may be present |
|
|
Why does the loop need to cool before picking up a bacteria? |
This will ensure that viable cells are transferred |
|
|
Prior to inserting a cooled loop or needle into a culture tube, what happens? |
The cap is removed and the mouth of the tube may be flamed |
|
|
If the tube is a broth tube, how is the loop inserted? |
The loop is inserted directly into the broth and twisted several times to ensure that the organisms on the loop are delivered to the liquid |
|
|
If the tube is an agar slant, the surface of the slant is inoculated how? |
By drawing the loop up the surface of the slant from the bottom of the slant to its top |
|
|
After the culture is inoculated, what do you do to the tube? |
The mouth of the tube may be reflamed and the tube is recapped |
|
|
What is used to inoculate or streak petri plates? |
Loops |
|
|
Why is the plate cover raised and held diagonally over the plate? |
To protect the surface from any contamination in the air |
|
|
How do you inoculate a petri dish? |
The loop containing the inoculum is then streaked gently over the surface of the agar; it is important to not gouge or disturb the surface of the agar |
|
|
Where should the loop never be placed? |
On the desktop surface |
|
|
When all wok is done for the day, what happens? |
The work area is treated with disinfectant to insure that any organism that might have been deposited during any of the procedures is killed |
|
|
What was the 2 aseptic techniques that we did? |
Broth culture to broth tube and agar plate to agar slant |
|
|
How does bacteria exist? |
In natural environments as mixed population |
|
|
Do bacteria occur as single species? |
It is extremely rare |
|
|
Who was the father of medical microbiology? |
Robert Koch |
|
|
What is a pure culture? |
It is a culture that only contains a single kind of an organism |
|
|
What is a mixed culture? |
A culture that contains more than one kind of organism |
|
|
What is a contaminated culture? |
A culture that contains a desired organism but also unwanted organisms |
|
|
What can we study about an individual organism of a pure culture? |
The cultural, morphological, and physiological characteristics |
|
|
What are two commonly used procedures for obtaining pure cultures? |
Steak plate and the pour plate |
|
|
What is the common thing between the streak plate and pour plate procedures? |
Both procedures involve diluting the bacterial cells in a sample to an end point where a single cell divides, giving rise to a single pure colony. |
|
|
What is a pure colony? |
it is assumed to be the identical progeny of the original cell and can be picked and used for further study of the bacterium |
|
|
How can bacteria be differentiated? |
Color, shape, stains |
|
|
Good smears are critical for discerning what? |
The morphology of cells, such as rods, cocci, and commas; The arrangement of cells, such as single cells, chains, or bunches; internal structures, such as endospores and inclusions |
|
|
What is the first goal of preparing a good stain? |
to cause the cells to adhere to the microscope slide so that they are not washed off during the staining and washing procedures |
|
|
What is the second goal of preparing a good stain? |
it is important to insure that shrinkage of cells does not occur during staining, otherwise distortion and artifacts can result |
|
|
What is the third goal of preparing a good smear? |
To prepare thin smears because the thickness of the smear will determine if you can visualize the individual cells, their arrangement, or details regarding microstructuers associated with cells |
|
|
Streptococci have what arrangement? |
Circular cells in a chain |
|
|
Staphylococcus have what arrangement? |
Circular cells in a cluster |
|
|
What ar epolyphosphate granules? |
Volutin or metachromatic granules; these are important for identifying organisms |
|
|
Why are thick smears not wanted? |
They can obscure details about arrangement and the presence of internal structures; stain can become entrapped in the clumps of cells, preventing its removal by destaining and washing |
|
|
What is the first step of preparing a bacterial smear if the bacteria are growing in a liquid medium? |
One starts by placing two or more loop fulls of the liquid medium directly on the slide |
|
|
What is the first step in preparing a bacterial smear from a solid media? |
one starts by placing one of two loopfulls of water on the slide and then using an inoculating loop to disperse the organisms in the water |
|
|
Why does water needed to be added to bacteria growing on solid media? |
The bacteria growing will cling to each other and become to thick unless sufficiently dispersed by water |
|
|
How much bacteria does it take to make a good smear? |
A very small amount |
|
|
What are bacterial cells mostly composed of? |
Water (80%) |
|
|
Why is it extremely difficult to visualize cells or their internal details in an aqueous suspension? |
Since they are 80% water there is very little contrast and hence definition between the cell and the surrounding aqueous environment in which most cells occur; this contrast makes it difficult to visualize cells |
|
|
How do we enhance the contrast of bacterial cells so they can be visualized? |
A smear of cells is prepared on a microscope slide which is heat fixed |
|
|
What does heat-fixing do? |
It causes the bacteria to adhere to the slide and preserve the structural integrity of the cells |
|
|
Why are stains used? |
To enhance cell features and the structures |
|
|
The use of single stain to color a bacterial cell is referred to as what? |
Simple staining |
|
|
What are some commonly used dyes? |
methylene blue, basic fuchsin, and crystal violet |
|
|
What are methylene blue, basic fuchsin, and crystal violet referred to as and why? |
Basic dyes because they have color bearing ionic groups that are positively charged |
|
|
What are chromophores? |
Color bearing ionic groups |
|
|
What are positively charged chromophores called? |
Cationic |
|
|
What do basic dyes work well with? |
bacterial cells that have chemical groups on their surfaces that confer a net negative charge to the cell |
|
|
Between the cell and the cationic chromophore of the stain, what type of attraction is there? |
Electrostatic |
|
|
What type of chromophores does acidic dyes have? |
anionic chromophores |
|
|
What type of chromophores does basic dyes have? |
cationic chromophores |
|
|
What is an example of an acidic dye? |
Eosin |
|
|
What can simple stains be used to determine? |
The morphology of bacterial cells |
|
|
What are the three morphological types? |
Bacilli, cocci, and spirals |
|
|
What can have rounded, flat or tapered ends? |
Rods or bacilli |
|
|
Where are rods prevalent? |
Human mouth |
|
|
These may occur singally, in chains, tetrads, or in masses |
Cocci |
|
|
What cocci occur in chains? |
Streptococci |
|
|
What cocci occur in bunches or clusters? |
Staphylococci |
|
|
What can exists as spirochaetes, spiruillum, or as comma shaped? |
Spiral cells |
|
|
What is the causative agent of syphillyis? |
Treponema pallidum |
|
|
What is the bacteria responsible for cholera and what shape is it? |
Vibrio cholera and shape is vibrio |
|
|
What is negative stains useful for? |
Studying the morphology of bacterial cells and characterizing some of the external structures (capsules), determining cell dimensions, and observing spirochaetes |
|
|
are negative stains basic or acidic? |
Acidic |
|
|
What is the charge of a negative stain? |
Negative |
|
|
What does not penetrate the cell but rather is repelled by the similarly charged bacterial cell? |
The negatively charged chromophore of the negative stain |
|
|
What is the background like in a negative stain? |
Dark and colored |
|
|
What do the cells appear as in negative staining? |
As transparent object against a dark background |
|
|
What are examples of negative staining? |
India ink and nirgrosin |
|
|
What does the negative stain procedure deal with? |
It consists of mixing the organism with a small amount of stain and spreading a ver thin film over the surface of a microscope slide |
|
|
Do you heat fix a negatively stained slide? |
No |
|
|
What can negative staining sometimes be combined with? |
Negative staining can be combined with positive staining to better demonstrate structures such as capsules |
|
|
why is heat fixing not performed on negative staining? |
Because there is no shrinkage of cell and the size determinations is more accurate |
