Culture Media Prof. Dr. Ihab Moussa

Culture Media 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.

Classification of Media Based on the consistency : Solid media Semisolid media Liquid media

Classification Based on the function or property: - Simple media - Enriched media - Enrichment broth - Selective media - Indicator media - Differential media - Composite media - Transport media

Constituents Of Media Agar or agar- agar Peptone - mixture of partially digested proteins Yeast or meat extract NaCl Melting point : 98°C Solidifying point : 42°C % of agar : Solid media (2%)

Simple Media Also called Basal medium Most commonly used in routine labs. e.g. Nutrient broth, NA

Enriched Media Blood, serum or egg added to the basal medium. To grow bacteria which are more exacting in nutritional requirements. e.g. Blood Agar, Chocolate Agar

Blood Agar Media

Enrichment Broth (media) For mixed cultures or materials containing more than one bacterium. Contains substances which stimulates wanted bacteria & inhibits unwanted bacteria. e.g. Tetrathionate broth

Selective Media Substances added to a solid media to favour the growth of wanted bacteria. e.g. MacConkey agar media

Indicator Media Change in the colour of indicator with the growth of bacteria. e.g. Sulphite in Wilson Blair media for Salmonella typhi.

Differential Media To bring out differing characteristics of bacteria. e.g. MacConkey’s agar

Dr Ekta, Microbiology, GMCA Composite Media For identification of isolates e.g. Triple Sugar Iron Transport Media For delicate organisms Delay in transit e.g. Stuart’s transport media Oct 07 Dr Ekta, Microbiology, GMCA