CULTURE MEDIA and STERILIZATION

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• وَقُل رَّبِّ أَدْخِلْنِي مُدْخَلَ صِدْقٍ وَأَخْرِجْنِي مُخْرَجَ صِدْقٍ وَاجْعَل لِّي مِن لَّدُنكَ سُلْطَانًا نَّصِيرًا
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• سورة الاسراء
• الآيات (80)
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CULTURE MEDIA

and
STERILIZATION

• CULTURE MEDIA

• Contain nutrients that support microbial growth.

• Isolation, growing and identification of microorganisms.

• Culture Vs culture medium?

• Common ingredients of culture media

• 1. PEPTONE
• 2. Meat extract
• 3. Nacl
• 4. Agar agar
• a. Melting point 92-95 c
• b. solidifying point 42-45 c
• c. concentration 1.5-2% (solid)
• 0.4- 0.8% (semisolid)

Nutrient agar

• Liquid (fluid media) e.g. nutrient broth.

• Solid media e.g nutrient agar, blood agar.
• Semisolid media.

• A. PHYSICAL STATE(CONSISTENCY)OF MEDIA

• Fluid

• Nutrient broth
• Peptone water
• Brain heart infusion

• Solid

Nutrient agar
Blood agar
Chocolate agar
MacConkey agar
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• Simple media e.g. nutrient agar and nutrient broth.

• 2) Special – purpose media
B. Use of the media





• Simple media enriched with appropriate substance ,e.g. Blood ,glucose ,serum and ascetic fluid , most commonly used to cultivate fastidious microorganism like Streptococci.
• Special – purpose media
• A) Enriched media










• Contain inhibitory substance ( e.g. bile salt , antibiotic, dyes … etc) which favour the growth of concerned microorganism and inhibit the growth of other . e.g. Mannitol Salt agar and MacConkey's agar.
• Special – purpose media
• B) selective media

Mannitol Salt Agar

• Selective medium for gram negative bacilli (contains bile salts which inhibit the growth of gram positive microorganisms)




• Certain species produce characteristic growth that can be easily recognized, or can produce certain effects in the media e.g. hemolytic and non-hemolytic species on blood agar ,MacConkeys agar differentiates between lactose fermenter and non lactose fermenter gram negative bacilli, nutrient agar differentiates between species of genus Staphylococcus
2) Special - Purpose medium

C) Differential media

Mannitol Salt Agar

• Non haemolytic

• bacteria on blood agar

• Staphylococcus citreus (lemon yellow colonies) on nutrient agar

• Antibiotic sensitivity test on Mueller-Hinton agar

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• Is the destruction or removal of all living organisms in or on an object

• DISINFECTION
• Is the destruction of pathogenic microorganism only





• 1. PHYSICAL METHODS
• 2. CHEMICAL METHOD

• PHYSICAL METHOD

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• a. At a temperature below 100 c e.g. pasteurization of milk

• b. At a temperature of 100 c
• I. Boiling at 100 c for 5-10 min
• II. Steaming at 100 c e.g. Tyndallization
• c. At a temperature above 100 c e.g. auto clave











• 1)Direct sun light
• 2)Ultra violet light
• 3)Ionizing radiation

• A-DISINFECTANTS e.g. acids(toxic to living tissue)

• B-ANTISEPTICS e.g. chlorine and iodine(safely applied to living (tissue

• 1.Chemical indicators

• Control tubes Browne’ s sterilization
• 2.Adhesive tape
• Bowie ---dick auto clave tape test