Culture medium
1. BASAL MEDIA.
- Basal media are those that may be used for growth (culture) of bacteria that do not need enrichment of the media.
- Examples: Nutrient broth, nutrient agar and peptone water.
- Staphylococcus and Enterobacteriaceae grow in these media.
2. ENRICHED MEDIA.
- The media are enriched usually by adding blood, serum or egg
- Contain substances that slow or inhibit the growth of micro-organisms other than those for which media are devised.
- Examples: Enriched media are blood agar, Chocolate agar, Monsour’s taurocholate , Tetrathionate broth and Lowenstein-Jensen media.
- Streptococci grow in blood agar media.
- Selenite F broth is an enrichment media used for the isolation of Salmonella group of bacteria.
- Tellurite medium for diphtheria, Deoxycholate citrate agar for Shigella and Salmonella.
- Alkaline peptone water for cholera
3. SELECTIVE MEDIA.
- These media favour the growth of a particular bacterium by inhibiting the growth of undesired bacteria and allowing growth of desirable bacteria.
- Examples: MacConkey agar, Lowenstein-Jensen media, tellurite media (Tellurite inhibits the growth of most of the throat organisms except diphtheria bacilli).
- Antibiotic may be added to a medium for inhibition.
|
Bacteria |
Selective medium |
|
Staphylococci |
Ludlam’s |
|
B.cereus |
MYPA |
|
B.anthrax |
PLET |
|
Legionella |
BYCE |
|
Borrelia |
BSK |
|
H.influenzae |
Flide’s |
|
Pseudomonas |
Cetrimide |
|
Brucella |
Serum potato infusion Trypticase soy agar |
|
Neisseria |
Thayer-Martin Mueller-Hinton |
|
Clostridium |
Robertson cooked meat |
|
Corynebacteriurn |
Loeffler’s serum slope Tinsdale, cysteine tellurite blood agar |
|
Campylobacter |
Skirrow’s |
|
Mycobacteria |
LJ media |
|
Shigella |
Deoxycholate citrate agar(DCA) |
|
Nocardia |
Paraffin bait |
|
Chlamydia |
Irradiated McCoy cells, He La cells |
|
V parahemolyticus |
Wagatsuma agar |
4. INDICATOR (DIFFERENTIAL) MEDIA.
- An indicator is included in the medium.
- A particular organism causes change in the indicator, e.g. blood, neutral red, tellurite.
- Examples: Blood agar and MacConkey agar are indicator media.
5. TRANSPORT MEDIA.
- These media are used when specie-men cannot be cultured soon after collection.
- Examples: Cary-Blair medium, Amies medium, Stuart medium.
|
Bacteria |
Transport media |
|
Str.pyogenes |
Pike’s media |
|
Gonococci |
Stuart’s media |
|
V.cholerae |
Cary-Blair, Venkatraman-Ramakrishnan |
|
Shigella |
Sach’s buffered glycerol saline |
6. STORAGE MEDIA.
- Media used for storing the bacteria for a long period of time.
- Examples: Egg saline medium, chalk cooked meat broth.
Exam Important
- Nutrient broth is basal medium
- Alkaline peptone water for cholera
- M tuberculosis – LJ medium
- Pseudomonas’s selective media is Cetrimide agar
- Enriched media are blood agar, Chocolate agar, Monsour’s taurocholate , Tetrathionate broth and Lowenstein-Jensen media.
- Selenite F broth is an enrichment media for Salmonella and Shigella.
- TCBS Agar is highly selective for the isolation of V. cholerae and V. parahaemolyticus as well as other vibrios
- Thayer – martin medium for selective medium for meningococcal infection and N. gonorrhoeae.
- Selective medium for Naegleria fowleri is nutrient agar rich with E coli
- Selective medium for shigella hektoen agar
- Loffler’s medium os enriched media
- Mac Conkey’s Agar is differential medium
- Transport medium are used for stool specimen :- Cary Blair medium, buffered glycerol saline or Stuart medium.
