Culture Media & Culture Techniques Flashcards
Indications/ Need for culture
- Isolate bacteria in pure cultures.
- Demonstrate their properties.
- Obtain sufficient growth for preparation of antigens & for other tests.
- Typing bacterial isolates.
- Antibiotic sensitivity.
- Estimate viable counts.
- Maintain stock cultures.
The original media used by Louis Pasteur
urine or meat broth
Liquid medium
diffuse growth
Solid medium
discrete colonies
cooked cut potato as early solid medium
Robert Koch
discovered agar
Walther Hesse
Classification of Media
Based on the consistency :
Solid media
Semisolid media
Liquid media
- contains 2% agar
- Colony morphology, pigmentation, hemolysis can be appreciated.
Solid media
ex. of Solid media
Nutrient agar, Blood agar
- no agar.
Liquid media
0.5% agar
Semi solid medium
Classification
Based on the function or property:
- Simple media
- Enriched media
- Enrichment broth
- Selective media
- Indicator media
- Differential media
- Composite media
- Transport media
mixture of partially digested proteins
Peptone
Melting point
98°C
Solidifying point
42°C
Simple Media also called
Basal medium
Most commonly used in routine labs
Simple Media
Blood, serum or egg added to the basal medium
Enriched Media
used to grow bacteria which are more exacting in nutritional requirements
Enriched Media
For mixed cultures or materials containing more than one bacterium
Enrichment Broth
Contains substances which stimulates wanted bacteria & inhibits unwanted bacteria
Enrichment Broth
Substances added to a solid media to favour the growth of wanted bacteria.
Selective Media
for V. cholerae
Thiosulfate-citrate-bile salts-sucrose agar
For fungal culture and some bacteria
PDA – potato dextrose agar
Fungi and yeast and also filamentous bacteria
Sabouraud Dextrose Agar (SDA)
Change in the colour of indicator with the growth of bacteria
Indicator Media
To bring out differing characteristics of bacteria.
Differential Media
a nutrient blend used to support microbial growth
Medium
The principle of sterilization in an ____________ is that steam under pressure is used to produce a temperature of __________ which if held for 15 minutes all microorganisms including bacterial endospores will be destroyed.
autoclave; 121ºC
Heat to redness in Bunsen burner flame
Wire loop
Each plate requires _______________ of agar
15-20 mL
Each tube requires _____________ of broth/agar
5-10 mL
- For inoculum preparation, Blood culture, for the isolation of pathogens from a mixture.
Liquid media
ex. of liquid media
Nutrient broth
ex. of Semi solid medium
motility medium
Constituents Of Media
- Agar or agar- agar
- Peptone - mixture of partially digested proteins
- Yeast or meat extract
- NaCl
ex. of Enriched Media
Blood Agar, Chocolate Agar
ex. of Enrichment Broth (media)
Tetrathionate broth
