Media exists in three different forms. They are:
- Solid culture media.
- Semisolid culture media.
- Fluid culture media.
Solid culture media:
- Mainly used in petri dishes as plate cultures.
- Can also be used in bottles or tubes as stab (deep) or slope cultures.
- Usually contain a concentration of 1-2% agar to yield a suitable gel.
- Used to observe the colonial appearance, shape, size of colony, and the changes in the surrounding medium.
- Helps to identify bacteria and differentiate commensals from pathogens.
- Examples : nutrient agar, blood agar, chocolate agar, etc.
| Medium | Main uses |
| Blood agar | Enriched medium for culturing wide range of pathogens.
Detecting haemolytic bacteria. Notes: crystal violet blood agar for beta- haemolytic streptococci. Kanamycin and neomysin blood agar for anaerobes. Chocolate (heated blood) agar for Haemophilus influenzae and Neisseria species. |
| Butzler medium
|
Selective and enriched medium for isolating Campylobacter species from faeces. |
| Charcoal cephalexin blood agar (CCBA) | Selective and enriched medium for Bordetella species |
| Deoxycholate citrate agar (DCA) | Selective and differential medium for enteric pathogens. |
| DNase agar | Biochemical medium for identifying Staphylococcus aureus. |
| Dorset egg medium
|
Enriched medium for Corynebacterium diphtheria to show volutin granules. |
| Kligler iron agar (KIA) | Differential medium for Salmonella and Shigella species. |
| Lactose egg yolk milk agar | Identifying Clostridium perfringens |
| Loeffler serum medium | Enriched medium for Corynebacterium diptheriae to show volutin granules. |
| Lowenstein Jensen acid medium | Culturing Mycobacterium tuberculosis |
| Mac Conkey agar | Differentiating lactose and non-lactose fermenter. |
| Malt extract cycloheximide agar | Selective and enriched media for ringworm fungi. |
| Mannitol salt agar | Differential and selective media for Staphylococcus aureus. |
| Modified new york city medium (MNYC) | Selective and enriched medium for Neisseria gonorrhoea. |
| Modified Tinsdale medium (MTM) | Selective and differenetial medium for Corynebacterium diphtheriae. |
| Motility indole urea medium (MIU) | Motility medium for enterobacteriaceae. |
| Nutrient agar | Culturing bacteria which don’t have special nutrients requirements. |
| Phenylalanine agar | Differentiating Proteus and Providencia from other enterobacteriaceae except Yersinia enterocolitis. |
| Sabouraud agar | Culturing fungi
|
| Tellurite blood agar | Selective medium for Corynebacterium diphtheria. |
|
Thiosulphate citrate bile salt agar (TCBs) |
Selective and differential medium for Vibrio cholera and other Vibrio species.
|
| Tryptone soya medium (diphasic) | Culturing pathogens in blood. |
| Xylose lysine deoxycholate (XLD) agar | Differentiating Salmonella and Shigella species. |
Semisolid culture media
- Prepared by adding small amount of agar (0.2-0.5% W/V) to a fluid medium.
- Mainly used as transport media and for motility testing.
- Examples: Amies transport medium, Cary- Blair transport medium, etc
| Medium | Main uses |
| Amies transport medium | For Neisseria gonorrhea and for other pathogens. |
| Cary- Blair transport medium | For pathogens (Salmonella, Shigella, Vibrio, Yersinia and Campylobacter) |
| Viral transport medium | Transport medium for viruses. |
| SIM medium | Test the sulphur reduction, indole production and motility for various pathogens. |
Image source: microbeonline
Fluid culture media
- Do not contain agar or solidifying agent.
- Growth is shown by presence of turbidity in the medium.
- Mainly used as enrichment media, biochemical testing media, and blood culture media.
- Examples: tryptone broth, selenite F broth, nutrient broth, etc.
| Medium | Main uses |
| Alkaline peptone water | Enrichment and transport medium for Vibrio cholerae |
| Christensen’s urea broth | For detecting urease activity of Proteus species. |
| Cooked meat medium (CMM) | Culturing anaerobes and maintaining control strains of bacteria. |
| Glucose phosphate peptone water | Culturing enterobateria in the Voges- Proskaeur test |
| Koser citrate medium | Detecting citrate utilization in differentiating enterobacteria from other bacteria |
| Litmus milk medium | Identifying enterococci and some other Clostridium species. |
| Nitrate broth | Detecting nitrate reduction in differentiating Mycobacterium species and Gram negative bacteria. |
| Peptone water sugars | Carbohydrate testing medium for differentiating enteric pathogens. |
| Selenite F broth | Enrichment medium for Salmonella species in faeces and urine. |
| Thioglycollate broth | Culturing anaerobes in blood. |
| Todd –Hewitt broth | Culturing beta- haemolytic Streptococci and other bacteria. |
| Tryptone water | Detecting indole production, especially of Escherichia coli. |
References:
i) https://microbeonline.com/types-of-bacteriological-culture-medium/
ii) https://www.slideshare.net/HiwrHastear/types-of-culture-media
iii) https://www.labtestsguide.com/culture