Microbiology Flashcards
TRUE OR FALSE: The Study of Microbiology includes the fundamental research on the physiology, biochemistry, cell biology, ecology, evolution and clinical aspects of the micro- organism and how the human body reacts to
these organism
True
What type of stain is the GRAM STAIN?
Differential Stain (It is a differential stain allowing to distinguish between the two main classes of bacteria (gram positives vs. gram negatives) by virtue of the cell wall. It also allows visualization of the morphology and cellular arrangement of the microorganism
TRUE or FALSE: Fixation of the specimen onto the slide is done by either application of heat or by using ethanol.
False (Uses HEAT or METHANOL)
Which among the following is the primary stain used in GRAM’S STAIN?
a. Crystal Violet
b. Hematoxylin
c. Iodine
d. Methylene Blue
e. Safranin
a. Crystal Violet
TRUE or FALSE: The Mordant is important to allow chemically binding of the acidic dye to the bacterial cell wall.
True. The mordant is used to allow binding of the ALKALINE dye (which is Crystal Violet) to the bacterial cell wall.
The most commonly used decolorizer in the GRAM’S STAIN.
a. Ethyl Alcohol
b. Acetone
c. Xylene
d. Acid Alcohol –
e. Glacial Acetic Acid
b. Acetone
Ethyl Alcohol – also a decolorizing agent
Xylene – more commonly used as a clearing agent in slide preparation
Acid Alcohol – used to remove excess stain and define nuclei following hematoxylin staining; 3% acid alcohol (used in Acid-Fast Staining as decolorizer)
Glacial Acetic Acid – fixative (slide preparation)
We use this counter stain in the Gram Stain Procedure.
a. Fuschin
b. Eosin
c. Safranin
d. Congo Red
c. Safranin
Fuschin – commonly used in the Ziehl- Neelsen staining technique
Eosin – most often used as a counterstain to hematoxylin in H&E staining
Congo Red – standard stain used in most
histopathology laboratories to identify amyloid material in tissues.
Gram Positive organisms have this gram stain reaction.
Purple
Gram positive stain reaction is due to what structure in the bacterial cell wall?
GRAM POSITIVE
Highly cross-linked thick peptidoglycan layer (murein layer) with numerous teichoic acid cross linkages is a feature of a gram positive cell wall
Lancet shaped diplococcus with clear areas surrounding it due to the presence of the capsules which is important for the pathogenesis of this organism
Streptococcus pneumoniae
- Extracellular diplococci
- coffee-bean shaped
Neisseria meningitidis
Staphylococcus aureus morphology characteristics
- Large opaque creamy white to yellow colonies
- Beta hemolysis on BAP
- Golden yellow on MSA
