Gram staining Flashcards
What are the two types of stains that can be done to bacteria
Simple and a differential
What is a simple stain
it is where only one stain is used to show the shape of the bacteria
What is a differential stain
it is a stain that is used to see if the bacteria is gram positive or negative
What is an acid fast stain
a is a stain that is used to see if the bacteria is acid fast or non acid fastit is acid fastness is due to the lipid (mycolic acid) rich in some bacterial cell walls. this is demonstrated by resistance to decolorization by mineral acid or alcohol after staining with hot strong carbol fuchsin.
What are some of the key points in the staining of bacteria
charging the loop - adding the specimen to the loop and add it to the slide by making a smear.
you can dry it through the flame or air dry
fixing the smear is done through putting the slide over the blue part of the flame. its hope to reduce getting extra toxics on the slide
What are the steps of an gram stain
the primary dye is crystal violet - 1 minute
Iodine - Mordant ( helps to fix iodine complex) - 1 minute
Decolorization is a sensitive step. if you don’t expose for the right amount of time, it can give you the wrong stain. you use Alcohol or acetone. the alcohol is for a minute and acetone is for 15 to 20 seconds.
Secondary stain or the Counter stain —> dol carbon fusion.
What are the colors of the stain
Red - negative
Purple - positive
What is the cell wall of bacteria made of
peptidoglycan
What is the difference between gram positive and negative of the cell wall
positive is 10 layer thick - also has teichoic acid
negative is 1 to 2 layers thick - the outer membrane is composed of lipids, polysaccharides, lipoprotein and lipiplysaccharides
What is the function of the teichoic acid
they play a role in inducing host inflammation. they play a part in induction of septic shock by certain positive bacteria. it also plays a part in attachment of staphylococci to infection site.
What is the function of the other membrane of the cell wall for gran negative bacteria
the outer membrane protects the peptidoglycan from the effects of lysozyme and impedes the entry of many antibiotics.
The lipopolysaccharides of the bacteria are compose of what
Lipid A
Core Polysaccharide
Outer polysaccharide
and there is a periplasmic space
What is lipid A
an Endotoxin that is responsible for toxic effects and when released in the blood stream that may give endotoxic shock.
What are the steps of the acid fast stain
we use the Ziechl- Neelsen method. in the method the decolorzier is H2SO4.
strong carbol fuchsin ( flood)
add conc H2SO4
methylene blue or malachite green
Cryptosporidium —> kinyoun stain or a modified stain that is used for oocyst
