What are consequences of Overstaining?
(Overstaining the bacterial smear may cause the cell wall disruption or totally destroy the cell wall which results in the loss of true morphological characteristics of the bacterial cell) 2. What is the consequence of leaving a stain on the bacterial smear too short (under-staining)?
Why is it not necessary to include a negative control for this stain procedure?
why is it not necessary to include a negative control for the endospore stain procedure? because an endospore stain is a differential type of staining procedure. it allows us to see both spores and vegetative cells. therefore, including a separate negative control consisting of only vegetative cells isn’t necessary.
How can you tell if an Endospore is positive or negative?
positive/negative: endospores stain green and may be seen inside cells or outside cells. endospore negative cells stain red with no evidence of green staining. ex. bacillus subtilis and clostridium are examples of endospore positive bacteria.
Why is it better to use an older bacillus culture for this exercise?
why does the gram stain work the way it does? why does the endospore stain call for an older (5-day) culture of Bacillus species? older bacteria are under greater nutritional stress so there will be more endospores present. what does a positive result for the spore stain indicate about the organism?
Why is an acid fast stain used so much less frequently than a gram stain?
Why is the acid fast stain not as widely used as the gram stain? very few bacteria are acid fast positive, so the test is less useful than a gram stain, which separates organisms into two large groups.
What color is acid fast bacteria?
Acid fast bacteria will be red, while nonacid fast bacteria will stain blue/green with the counterstain with the Kinyoun stain.
What is the shape of an acid fast bacteria?
This group of rod‐shaped bacteria possesses large amounts of mycolic acid in the cell wall. The presence of mycolic acid makes the bacteria very difficult to stain, but when heat or other agents are used to force carbolfuchsin into the cytoplasm, the bacteria resist decolorization with a dilute acid‐alcohol solution.
Are acid fast bacteria Gram positive or negative?
Acid-fast bacteria are gram-positive in terms of structure because they contain peptidoglycan in the cell wall. However, they stain poorly with Gram stain procedure, appearing weakly Gram-positive.
What bacteria Cannot be Gram stained?
Atypical bacteria are bacteria that do not color with gram-staining but rather remain colorless: they are neither Gram-positive nor Gram-negative. These include the Chlamydiaceae, Legionella and the Mycoplasmataceae (including mycoplasma and ureaplasma); the Rickettsiaceae are also often considered atypical.
Is E coli acid-fast positive or negative?
Escherichia coli is a NON ACID-FAST bacterium. (1) Bacteria are DECOLORIZES by ACID ALCOHOL and DO NOT retain the initial stain, carbolfuchsin, (2) so it can pick up the counterstain, METHYLENE BLUE.
What diseases are caused by acid-fast bacteria?
Acid-fast bacillus (AFB) is a type of bacteria that causes tuberculosis and certain other infections. Tuberculosis, commonly known as TB, is a serious bacterial infection that mainly affects the lungs. It can also affect other parts of the body, including the brain, spine, and kidneys.
What happens if AFB is positive?
A positive AFB smear or culture several weeks after drug treatment has started may mean that the treatment regimen is not effective and needs to be changed. It also means that the person is still likely to be infectious and can pass the mycobacteria to others through coughing or sneezing.
What is the most likely reason for the poor appearance of the bacteria on this slide?
What is the most likely reason for the poor appearance of the bacteria on this slide? The slide was heat fixed for too long.
Why is there a need to fix the bacteria to the slide?
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 will happen if you Gram stain cells of an old culture?
Gram stain is reliable only on cells from cultures that are in the exponential phase of growth. Older cultures contain more ruptured and dead cells. Cells from old cultures may stain Gram negative even if the bacteria are Gram positive.
Why is it important to air dry the slide before heat fixing?
Drying helps remove excess water to ensure optimal heat fixation. Air-drying adheres the bacteria to the slide. Air-drying ensures that the smear is thin enough to stain. Drying helps remove excess water to ensure optimal heat fixation.
What would happen if the slide did not dry completely before you heat fix it?
1. If you don’t completely air dry your slide, you will end up boiling your microorganisms when heat-fixing. 2. When mixing bacteria with water, if you over mix it can result in inaccurate cell patterns.
What happens if a slide is heat fixed for too long?
If you heat fix too little, the bacteria will wash off the slide. If you heat fix too much, you will cook the bacteria and denature them.
Why can’t you heat fix the smear until the smear is completely dries?
Air drying the smears before heat fixation is essential. Water can boil while passing the slide through the flame which could alter the natural shape and size of the bacteria. Overheating the smear during heat-fixing process can distort the form and structure of the cells.
Is it possible to wash off your cells after heat fixing?
If your heat fixing step is performed properly and your cells are still washing off the slide, one may use a drop of a protein solution (such a serum, skim milk, or media containing protein) instead of water to help stick your cells to the slide.
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 three things does heat fixing the smear accomplish?
Hows does Heat-Fixing work? It removes water from the bacterial cell, pores open in the cell so more stain can enter the cell wall….Terms in this set (139)
- causes the cells to adhere to the slide so it wont wash off.
- Kills the microorganisms.
- Causes changes in the bacterial cells which causes them to stain better.
What is the reason for heat fixing?
Heat fixation is a technique used in organism staining that is able to kill organisms, adhere them to the slides being used, and alter them so they can take on the stains being used. Fixing is a necessary step when performing a stain on a slide, explains Ohio State professor Stephen Abedon.
What are three or four reasons for heat fixing smear preps of bacteria?
What are two reasons why smears are heat fixed?…Terms in this set (12)
- Adding too much or too little bacteria.
- Over mixing bacteria with water.
- Overheating your slide and killing all bacteria.
- Not letting the air dry completely.
What are the three reasons for the heat fixing step when preparing bacterial smears?
Discuss the reasons for heat fixing bacterial smears prior to staining.
- To kill bacteria on slide;
- to make dye penetrate cells;
- to coagulate proteins of cells thus making cells stick to slide.