OSPE transport

Question 1

Tumbling motility

Answer 1

Listeria

Question 2

Gliding motility

Answer 2

Mycoplasma

Question 3

Stately motility

Answer 3

Escherichia coli, Clostridium

Question 4

Swarming motility

Answer 4

Proteus, Clostridium tetani

Question 5

Darting motility

Answer 5

Vibrio cholerae, Campylobacter

Question 6

Corkscrew, lashing, flexion
extension motility

Answer 6

Spirochetes

Question 7

non-motile bacteria

Answer 7

Klebsiella pneumoniae, and Yersinia pestis

Question 8

Name any other methods for demonstrating bacterial motility

Answer 8

mannitol motility medium
tannic acid staining(RYU’S method)

Question 9

why the edge of hanging drop is focused for examination.

Answer 9

Bacteria tend to accumulate at the edge of the drop. Once the edge is located, it is then observed under 40x high power objective.

Question 10

SIMPLE STAINING

Answer 10

Imparts only one color to all bacteria
Simple stains: Methylene blue, Basic fuchsin

Question 11

DIFFERENTIAL STAINING

Answer 11

Gram staining- Differentiates into gram-positive and gram-negative bacteria
Acid fast stain- Differentiates acid fast and non-acid fast groups

Question 12

SPECIAL STAINING

Answer 12

albert stain- dif bacteria with metachromatic granules fr other bacteria

negative staining-demonstrate capsule

impregnation method-silver impregnation to demonstrate thin organism like spirochetes

Question 13

GRAM-STAINING CLINICAL RELEVANCE

Answer 13

in general, Gram-positive bacteria are more susceptible to penicillin than Gram-negative bacteria, Gram- negative bacteria are intrinsically resistant to Vancomycin

Question 14

FIXATION

Answer 14

Chemical method : Blood smears- Ethanol, formaldehyde, methanol, glutaraldehyde

Heat fixation: Bacterial smears- gently flame heating an air dried smear

Question 15

Gram staining

Answer 15

Primary stain – Crystal violet
Mordant – Lugol’s iodine
Decolorizer – Alcohol or acetone
Counter stain - Safranin

Question 16

Primary stain

Answer 16

• The smear is stained with - crystal violet
  for one minute
• rinsed with water
• Crystal violet stains all the bacteria violet in color

Question 17

Mordant: Gram’s iodine

Answer 17

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

Question 18

Decolorization:

Answer 18

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)

Question 19

Counter stain

Answer 19

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

Question 20

Principle of Gram Staining

Answer 20

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