How do you prepare a bacterial smear?

SMEAR PREPARATION

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

Besides, how do you slide on a smear?

Place clean glass slide on a flat surface. Add one small drop of blood to one end.
Take another clean slide, and holding at an angle of about 45 deg, touch the blood with one end of the slide so the blood runs along the edge of the slide by capillary action.
Make 2 smears, allow to air dry, and label clearly.

Also, what are the other ways of fixing the bacteria to the slide? There are two methods of adhering your bacteria to the slide, heat fixation or methanol fixation. Heat fixing is only used with BSL1 organisms. The organisms we will be working with are BSL2, so you will need to use the methanol fixation technique.

Subsequently, one may also ask, why do we air dry and heat the bacterial smear prior to staining?

Before bacteria can be stained, a smear of bacteria must be made on a slide and heat fixed. Heat fixing denatures bacterial enzymes, preventing them from digesting cell parts, which causes the cell to break, a process called autolysis. The heat also enhances the adherence of bacterial cells to the slide.

What happens if you overheat a bacterial smear?

If the smear is overheated during heat fixing, the cell walls will rupture. Concentration and freshness of reagents may affect the quality of the stain. Washing and drying of the smear between steps should be consistent. Excess water left on the slide will dilute reagents, particularly Gram's iodine.

35 Related Question Answers Found

What is the purpose of a smear?

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.

Does heat fixing kill bacteria?

Heat fixing kills the bacteria in the smear, firmly adheres the smear to the slide, and allows the sample to more readily take up stains.

What is the purpose of simple staining?

The simple stain can be used to determine cell shape, size, and arrangement. True to its name, the simple stain is a very simple staining procedure involving only one stain. Since the surface of most bacterial cells is negatively charged, these positively charged stains adhere readily to the cell surface.

What advantages are there to observing unstained bacterial specimens?

Advantages. Brightfield microscopy is very simple to use with fewer adjustments needed to be made to view specimens. Some specimens can be viewed without staining and the optics used in the brightfield technique don't alter the color of the specimen.

Why mycobacteria are acid fast?

These Acid-fast organisms like Mycobacterium contain large amounts of lipid substances within their cell walls called mycolic acids. These acids resist staining by ordinary methods such as a Gram stain. It can also be used to stain a few other bacteria, such as Nocardia. Acid-fast bacilli are bright red after staining.

Why do we stain bacterial smears?

Because bacteria are, for the most part, transparent, we use stains to give them color for microscopic observation. Making a bacterial smear prepares the bacteria to be stained and is the first step of most staining procedures.

What is a stain in microbiology?

Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Biological staining is also used to mark cells in flow cytometry, and to flag proteins or nucleic acids in gel electrophoresis.

What are the characteristics of a good blood smear?

It should have a rainbow sheen when reflecting light. The smear should be smooth the entire length of the slide with no holes, lines or grainy appearance. The slide consists of a blood smear that is exactly one cell thick in the feathered edge when viewed microscopically.

What is a direct smear?

Direct fecal smear technique is the simplest and easiest technique to facilitate detection of intestinal parasites that infected subjects pass in their feces. A small amount of fresh feces is mixed with either saline (to detect the protozoa motility) or lugol/iodine solution (to reveal the parasite structure).

How does alcohol fix a blood smear?

Blood smears are fixed by dipping in absolute methanol or ethanol for 30 seconds.

How do I stop a thick smear?

Protect thick smears from hot environments to prevent heat-fixing the smear. Do not fix thick smears with methanol or heat. If there will be a delay in staining smears, dip the thick smear briefly in water to hemolyse the RBCs.

How do you stain a blood smear?

The dried smear is then fixed with methanol or ethyl alcohol and stained. The smear is covered with stain for approximately ten minutes, then diluted with water and allowed an additional ten minutes for the cells to properly stain. Following the stain application, the slide is rinsed under running water.

How do you prepare a smear for staining?

Preparation of the smear is as follows:

From broth: Using a cooled, sterile loop, place a loopful of broth on the slide and spread in a circular motion to about 1 cm in diameter.
From plated media: Place a drop of sterile water or saline on the slide. Select the isolated colony to be stained.

At what angle should you hold the spreader slide to make the smear?

Hold the spreader slide at 30-40 degrees to achieve optimal smear length. Maintain even contact throughout the spreading motion. Short smear • Use a larger droplet of blood. Decrease the angle of the spreader slide.

How do you examine a blood smear?

Examining a blood smear

Locate the optimal area for examination at higher magnification to perform a differential leukocyte count and examine morphologic features of blood cells.
To check that leukocytes are uniformly distributed throughout the smear and not excessively concentrated at the feathered edge.

How a smear is done?

A Pap smear is performed in your doctor's office and takes only a few minutes. Your doctor will gently insert an instrument called a speculum into your vagina. The speculum holds the walls of your vagina apart so that your doctor can easily see your cervix.

Is safranin positive or negative?

The purple, crystal-violet stained cells are referred to as gram-positive cells, while the red, safranin-dyed cells are gram-negative (Figure 3).