Lesson 12: CULTURE MEDIA Flashcards
Laboratory diagnosis of an infection is usually confirmed by isolating and culturing microorganisms in
Artificial media
developed the Petri dish (plate), a container for solid culture media.
Richard Petri
pioneered the use of
agar as a base for culture media
Robert Koch
the wife of Walther Hesse, one of Koch’s assistants who suggested the use of agar base for culture media.
Fannie Eilshemius Hesse,
developed the pour plate method and was the first to use solid culture media
for culture of bacteria.
Robert Koch
A nutrient material prepared for the growth of microorganisms in a laboratory is called a
culture medium
When microbes are introduced into a culture medium to initiate growth, they are called an
Inoculum
The microbes that grow and multiply in or on a culture medium are referred
to as a
Culture
is the process of growing microorganisms on culture media and obtained as pure cultures for study.
Cultivation
taking bacteria from the infection site
in vivo environment
by some means of specimen
collection and growing them in the artificial environment of the laboratory
in vitro environment
By appropriate procedures they have to
isolated cultivation
Purpose of bacterial cultivation
i. To grow and isolate all bacteria present in an infection.
ii. Infection and contaminants or colonizers
iii. Identification and characterization
Some of the components of culture media are as follows:
- Water
- Agar
- Peptone
- Yeast extract
- Malt extract
- Blood and serum
prepared from a variety of seaweeds and is now universally used for preparing solid media. Does not add to the nutritive properties of a medium and is not affected by the growth of bacteria. The melting and solidifying points of the solutions are not the same. At the concentrations normally used, most bacteriological melt at about 95°C and solidify only when
cooled to about 42°C.
Agar (or agar-agar)
Another almost universal ingredient of common media. It is a complex mixture of partially digested proteins. Commercially available digest broth can be used. Meat extract is also available commercially and is known as LabLemco.
Peptone
Tap is often suitable for culture media, particularly if it has a low mineral content, however glass-distilled or demineralized is best use
Water
It contains a wide range of amino acids, growth factors and inorganic salts. Used mainly as a comprehensive source of growth factors and may be substituted for meat extract in culture media.
Yeast extract
The important constituents peptone are
peptones, proteoses, amino acids, a variety of inorganic salts including phosphates, potassium and magnesium, and certain accessory growth factors such as nicotinic
acid and riboflavin.
consists mainly of maltose (about 50%), starch, dextrins and glucose, and contains about 5 percent of proteins and protein breakdown products, and a wide range of mineral salts and growth factors.
Malt extract
These are used for enriching culture media. Either human or animal blood can be used. Usually 5-10 percent blood is used and the most usual
concentration is 10 percent. Used in certain media.
Blood and serum
Classification of media
A. Phase of growth media
B. Based on Nutritional factor
C. Defined media
D. Special media
The earliest culture media. The original media used by Louis Pasteur were such as urine or meat. In this media, nutrients are dissolved in water, and bacterial growth is indicated by a change in appearance from clear to turbid, (i.e. cloudy).
Liquid (broth) media
