What is a properly prepared bacterial smear?

Published by Charlie Davidson on

What is a properly prepared bacterial smear?

A properly prepared smear accomplishes two things. It causes bacteria to adhere to a slide so that they can be stained and observed. It also kills them, rendering pathogenic bacteria safe to handle. An objective in preparing smears is to learn to recognize the correct density of bacteria to place on the slide.

What is the purpose of a smear preparation?

The preparation of a smear is required for many laboratory procedures, including the Gram-stain. The purpose of making a smear is to fix the bacteria onto the slide and to prevent the sample from being lost during a staining procedure. A smear can be prepared from a solid or broth medium.

What is the purpose of preparing a bacterial smear quizlet?

What is the purpose of a bacterial smear? Prepare a sample of bacteria that adheres to a slide. The sample can then be stained so as to better view the bacteria.

What happens if a smear is too thick?

PROBLEM: If the smear is too thick, the cells can appear Gram-positive in very thick area. PROBLEM: Over warming the smear (this happens most often when smears are warmed prior to being completely air dried, or when flaming too much to fix the slides) will cause all cells to appear Gram-negative.

What are the characteristics of a good bacterial smear?

What are the characteristics of a good smear? 1. Cells that adhere to the slide and does not wash off during staining and washing procedures.

How can you achieve a good bacterial smear?


  1. Place one needle of solid bacterial growth or two loops. of liquid bacterial growth in the center of a clean slide.
  2. If working from a solid medium, add one drop (and only one drop)
  3. Now, with your inoculating loop, mix the specimen with the water.
  4. Place the slide on a slide warmer and wait for it to dry.

Why is it important to air dry a smear?

Air-drying ensures that the smear is thin enough to stain. The air-drying step coagulates the proteins in the bacteria. Drying helps remove excess water to ensure optimal heat fixation.

What is a bacterial smear and how is it created?

Bacterial smear. – Obtaining bacteria, spreading it on a slide, and staining for microscopic examination. – Bacterial smear is the first step of the staining process. Accomplishments. Causes bacteria to adhere (attach) to slide allowing staining and observations.

What is the meaning of bacterial smear?

A bacterial smear is a thin layer of bacteria placed on a slide for staining. Preparing the smear requires attention to a number of details that help prevent contamination of the culture and ensure safety to the preparer.

Why is thick smear not fixed?

Thick smear. It is not fixed in methanol; this allows the red blood cells to be hemolyzed, and leukocytes and any malaria parasites present will be the only detectable elements. However, the hemolysis may lead to distorted plasmodial morphology making plasmodium species differentiation difficult.

What is the principle of Leishman stain?

Leishman stain contain methylene blue dye, a basic dye, which gives colour to an acidic component and eosin dye, an acidic dye, which gives colour to a basic component. These dyes differentiate the different component of blood. Leishman’s Stain belongs to the group of Romanowsky stains.

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