OSPE transport Flashcards
Tumbling motility
Listeria
Gliding motility
Mycoplasma
Stately motility
Escherichia coli, Clostridium
Swarming motility
Proteus, Clostridium tetani
Darting motility
Vibrio cholerae, Campylobacter
Corkscrew, lashing, flexion
extension motility
Spirochetes
non-motile bacteria
Klebsiella pneumoniae, and Yersinia pestis
Name any other methods for demonstrating bacterial motility
mannitol motility medium
tannic acid staining(RYU’S method)
why the edge of hanging drop is focused for examination.
Bacteria tend to accumulate at the edge of the drop. Once the edge is located, it is then observed under 40x high power objective.
SIMPLE STAINING
Imparts only one color to all bacteria
Simple stains: Methylene blue, Basic fuchsin
DIFFERENTIAL STAINING
Gram staining- Differentiates into gram-positive and gram-negative bacteria
Acid fast stain- Differentiates acid fast and non-acid fast groups
SPECIAL STAINING
albert stain- dif bacteria with metachromatic granules fr other bacteria
negative staining-demonstrate capsule
impregnation method-silver impregnation to demonstrate thin organism like spirochetes
GRAM-STAINING CLINICAL RELEVANCE
in general, Gram-positive bacteria are more susceptible to penicillin than Gram-negative bacteria, Gram- negative bacteria are intrinsically resistant to Vancomycin
FIXATION
Chemical method : Blood smears- Ethanol, formaldehyde, methanol, glutaraldehyde
Heat fixation: Bacterial smears- gently flame heating an air dried smear
Gram staining
Primary stain – Crystal violet
Mordant – Lugol’s iodine
Decolorizer – Alcohol or acetone
Counter stain - Safranin
Primary stain
- The smear is stained with - crystal violet
for one minute - rinsed with water
- Crystal violet stains all the bacteria violet in color
Mordant: Gram’s iodine
poured oven he slide for one minute rinsed with water
Iodine serves as mordant; it combines with the primary stain to form a dye-iodine complex which gets retained inside the cell
Decolorization:
pouring of few drops of decolorizer to the smear
e.g., Acetone (for 5 seconds) or Ethanol (20 seconds) or Acetone alcohol (for 10 seconds)
* immediately rinsed with water
* removes the primary stain from gram-negative bacteria while the gram-positive bacteria retain the primary stain
-gram-positive bacteria loose color (over decolorization)
- if poured for less time, the gram-negative bacteria do not lose the color of primary stan in properly (under decolorization)
Counter stain
Secondary stains- Safranin added for 30 seconds
* It imparts pink or red color to the gram-negative bacteria
The slide is rinsed in tap water, dried, and then examined under oil immersion objective lens
Principle of Gram Staining
Gram-positive cell wall has a thick peptidoglycan layer (50-100 layers thick), which are
tightly cross linked to each other
* The peptidoglycan itself is not stained but act as a permeability barrier preventing loss of crystal violet
* More so, alcohol is thought to shrink the pores of the thick peptidoglycan
Gram-negative cell wall is more permeable thus allowing the out flow of crystal violet easily, this is attributed to the thin peptidoglycan layer in Gram-negative cell wall which is not tightly cross linked
Presence of lipopolysaccharide layer in the cell wall of gram-negative bacteria, which gets disrupted easily by the action of acetone or alcohol; thus, allowing the primary stain to come out of the cytoplasm
