CULTURE MEDIA

CULTURE MEDIA: 

CULTURE MEDIA Dr.J.Lancy Associate Professor Govt medical college thrissur

DEFINITION: 

Culture media are artificial media in which essential nutrients are added to give satisfactory growth of bacteria. We need culture media to isolate pathogenic micro-organisms from clinical samples-urine,faeces,sputum,blood,CSF,pus etc DEFINITION

DISCOVERY: 

Original media introduced by LOUIS PASTEUR. All were liquid media. Solid media introduced by ROBERT KOCH. Agar-agar was used as the solidifying agent. DISCOVERY

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ROBERT KOCH. LOUIS PASTEUR.

AGAR-AGAR: 

Obtained from sea-weeds. Long chain polysaccharide. It has no nutrient value. Not affected by growth of bacteria. Melts at 98degrees Sets at 42degrees 2% agar –solid media 0.2-0.5% agar-semi solid medium 6% agar-prevents swarming AGAR-AGAR

UNIVERSAL INGREDIENTS: 

Agar-agar Peptone-partially digested proteins Meat extract- lab-lemco Yeast extract Blood-sheep,rabbit,human Serum Egg-albumin UNIVERSAL INGREDIENTS

TYPES OF MEDIA: 

Simple or basal medium Enriched medium Enrichment medium Selective medium Indicator medium Differential medium Sugar medium Transport medium Anaerobic medium TYPES OF MEDIA

SIMPLE OR BASAL MEDIUM: 

Peptone water-peptone+NaCl+distilled water-pH 7.2-7.6 Nutrient broth-peptone water+meat extract Nutrient agar-nutrient broth+2% agar Most common medium used in routine diagnostic laboratories for doing biochemical tests for identification of bacteria. SIMPLE OR BASAL MEDIUM

ENRICHED MEDIUM: 

Addition of blood or serum or egg albumin to basal medium.eg:blood agar,chocolate agar,egg media. Blood agar-nutrient agar+5-10%blood In blood agar,bacteria produce 2 types of hemolysis-alpha and beta. Alpha hemolysis-partial-streptococcus viridans,pneumococci. Beta-complete-staphylococci,strep.pyogenes ENRICHED MEDIUM

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blood agar

CHOCOLATE AGAR: 

Heated blood agar Prepared by heating blood agar at 75-80 degrees in a water bath until it becomes chocolate brown in colour. Required for the growth of Haemophilus influenzae. Egg medium is prepared by addition of egg albumin to basal medium CHOCOLATE AGAR

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CHOCOLATE AGAR

ENRICHMENT MEDIUM: 

Eg:Selenite F broth, Tetrathionate broth, Alkaline peptone water.-LIQUID MEDIUM In mixed cultures or materials containing more than one bacterium to be isolated is overgrown by unwanted bacteria. Certain substances are added into the medium which will stimulate the growth of pathogenic bacteria and inhibit the growth of unwanted bacteria. Pathogenic bacteria isolated in pure culture. ENRICHMENT MEDIUM

SELECTIVE MEDIUM: 

Solid medium in which inhibitory substances are added to inhibit the growth of unwanted bacteria. Deoxycholate citrate agar(DCA) and xylose lysin deoxycholate for salmonella and shigella. Thiosulfate citrate bile salt sucrose agar(TCBS)-for vibrio cholerae. SELECTIVE MEDIUM

INDICATOR MEDIUM: 

Certain indicator substances are added into the medium which changes colour when a bacterium grows on the medium WILSON AND BLAIR MEDIUM for Salmonella typhi-sulphite is reduced to sulphide-black colonies. Mc Leod’s medium(potassium tellurite agar)-Corynebacterium diphtheriae -tellurite is reduced to tellurium-black colonies INDICATOR MEDIUM

DIFFERENTIAL MEDIUM: 

Certain substances are incorporated in the medium to bring out different characteristics of bacteria to distinguish between them. Mac Conkey’s medium which contains peptone,lactose,agar,nuetral red and sodium taurocholate. Lactose fermenting bacteria produce pink colonies-E.coli and klebsiella. Non-lactose fermenting bacteria produce colourless colonies-Salmonella,Shigella. DIFFERENTIAL MEDIUM

TRANSPORT MEDIUM: 

Medium used for transporting clinical specimens containing delicate organisms which do not survive the time taken for transporting the material from the site of collection to the laboratory. Bacteria remain viable without multiplication. Stuart’s medium-gonococci Pike’s medium-streptococci Cary-Blair medium-vibrio cholerae Buffered glycerol saline-shigella TRANSPORT MEDIUM

SUGAR MEDIUM: 

Peptone water containing 1% sugar-glucose,lactose,sucrose,maltose, and mannitol. Fermentation of sugars produce acid and gas. Acid production detected by colour change. Gas production detected by Durham’s tube. SUGAR MEDIUM

ANAEROBIC MEDIUM: 

Medium used for growing anaerobic bacteria-Clostridium species. Robertson’s cooked meat medium contains glucose broth+cooked meat. Proteolytic organisms-the colour of meat-black.Eg:Clostridium tetani. Saccharolytic organisms-meat-pink.Eg:Clostridium perfringens Thioglycollate broth is also an anaerobic culture medium ANAEROBIC MEDIUM

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Robertson's cooked meat medium

STERILISATION OF CULTURE MEDIA: 

AUTOCLAVING at 121 degree for 15 min. Media which cannot be autoclaved-Selenite F broth and tetrathionate broth are sterilised by steaming at100 degrees. Lowenstein-Jensen’s medium for mycobacterium tuberculosis and Loeffler’s serum slope for Corynebacterium diphtheriae are sterilised by inspissation using inspissator at 80-85 degrees. STERILISATION OF CULTURE MEDIA

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AUTOCLAVE inspissator

GROWTH OF BACTERIA: 

In liquid medium,the bacterial growth is detected by turbidity. In solid medium,bacteria produce colonies. A colony means visible cluster of bacteria arising from a single parent cell. Pure culture is obtained by using solid medium. GROWTH OF BACTERIA

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Thank you