What is Culture Media?
The media is a source of nutrients to support the growth of the micro-organisms in-vitro. The media helps in the growth and counting of microbial cells, selection of microorganisms, and survival of microorganisms. The culture medium can be liquid or gel.
Common ingredients of culture media
- Peptone- source of carbon and nitrogen.
- Beef extract- source of amino acid, vitamins, minerals.
- Yeast extract- source of vitamin, carbon, nitrogen.
- Distilled water
- Agar- solidifying agent.
How to prepare culture media?
- Weigh the amount of ingredients powder on weighing machine.
- Dissolve the ingredients in distilled water.
- Adjust PH of the medium if needed.
- Add agar and boiled it to dissolve.
- Pour the media into flask.
- Autoclave the media when ingredients fully dissolve.
- Sterilization is done in autoclave to prevent from contamination, at 121ºC for 15 min at 15lbs.
- After the autoclave place the media flask in laminar air flow.
- Sterilize the laminar air flow with 70% alcohol.
- A bit cools down the media and pours into sterile Petri-plates for solidification.
- Then sample is ready to spread(spreader) / streak
- (Inoculation loop) on the medium for identification or isolation of microbes.
- Sealed the Petri plates with paraffin, label them.
- Keep them inverted in incubator at 37ºC for 24hrs.
- Observe the result next day colonies formation is visible on the media.
What is a Defined medium?
A defined medium has a known quantity of all ingredients, like carbon source (Glucose or Glycerol) and nitrogen source (Ammonium salt or Nitrate as inorganic nitrogen). The medium needs in metabolic, nutritional, and physiological growth experiments. (Czapek Dox Medium)
What is an Undefined medium?
What is Complex media?
This media is other than basal media; it has added ingredients to bring the characteristics of microorganisms with unique nutrients.
Types of culture media based on consistency/ physical state
1. Solid medium
2. Semi-solid medium
3. Liquid medium
1. Solid media
Principle of Solid Media
It is for the isolation of bacteria as a pure culture on a solid medium.
Robert Koch realized the use of solid media.
Agar is used to hardening the media at 1.5- 2.0% concentration. Solid media allows the growth of bacteria as colonies by streaking on the medium. It solidified at 37 degrees Celsius.
Agar is an un-branched polysaccharide extracted from red algae species like Gelidium. Colonies identification is done on this medium.
Examples of Solid Media
Growth of bacteria on solid medium appear as smooth, rough, mucoid, round, irregular, filamentous, punctiform.
2. Semi-solid media
Principle of Semi-solid media
This media shows the motility of bacteria and the cultivation of microaerophilic bacteria. This media has agar at a concentration of 0.5% or less. It has a jelly consistency.
Examples of Semi-solid media
Stuart’s and Amies media, Hugh and Leifson’s oxidation fermentation medium, and Mannitol motility media.
The growth of bacteria in semi-solid appears as a thick line in the medium.
3. Liquid media
Principle of Liquid media
This media shows the growth of a large number of bacteria.
It is called Broth that allows bacteria to grow uniformly with turbidity. The growth occurs at 37ºC in an incubator for 24hrs.
Liquid media don’t have the addition of agar; it is for fermentation studies.
Examples of Liquid media
Nutrient broth, Tryptic soy broth, MR-VP broth, phenol red carbohydrate broth.
Growth of bacteria in liquid media- Turbidity is seen at the end of the broth.
Types of culture media based on chemical composition/application
There are seven routine laboratory media.
- Basal media
- Enriched media
- Selective media
- Enrichment media
- Indicator media or differential media
- Transport media
- Storage media
1. Basal media
This media is simple as it enhances the growth of many microorganisms. It’s a routinely used medium in the lab, having Carbon and Nitrogen. This media allows the growth; of non- fastidious bacteria without any enrichment source; used for sub-culturing. It’s a non-selective medium.
Staphylococcus and Enterobacteriaceae grow in this media.
Examples of Basal media
Nutrient Agar, Peptone water.
2. Enriched media
This media requires the addition of other substances like blood, egg, or serum. An enriched media allows the growth of devised microorganisms but inhibits other and fastidious microbes grow as they require nutrients like vitamins and growth-promoting substances.
Example of Enriched media
Blood agar, Chocolate agar, LSS, Monsor’s taurocholate, Lowenstein Jensen media. Blood agar identifies hemolytic bacteria, chocolate media for N. gonorrhea.
3. Selective media
As by name, we can tell, this media shows the growth of selective; microbes or desired microorganisms and inhibits the growth of unwanted microbes. The inhibition occurs by adding bile salts, antibiotics, dyes, PH adjustments. Media is agar-based; any media is possible to transform into selective by adding inhibitory agar.
Examples of Selective media
|1.||Mannitol Agar– It has 7% of sodium chloride that inhibits the growth of other microbes and promotes the growth of Staphylococci. It has phenol red dye that produces acid Staphylococcus used the mannitol for the acid production and the color of phenol red changes from red to yellow.||Selective for Staphylococcus aureus|
|It is used for the isolation of Salmonella bacteria that causes typhoid.|
Selective for Shigella.
|3.||MacConkey Agar- It has bile salts that inhibit the growth of gram-positive bacteria||Selective isolation for Enterobacteriaceae|
|4.||TCBS Agar– Light green translucent media Bile salt inhibits the growth of unwanted bacteria||Selective for Vibrio cholera.|
V. cholera produces acid by fermentation of sucrose that acts as indicator called bromothymol blue and yellow colonies appears.
|5.||Lowenstein Jensen Media- It is made selective by adding malachite green and stops the unwanted growth of pathogens.||Selective for M. tuberculosis|
4. Enrichment media
It is a liquid medium, which also permits the growth of desired bacteria at a low density. The media provides an environment and conditions as selective media and inhibits unwanted bacteria from growing. It is for the isolation of the soil and fecal microorganisms.
Examples of Enrichment media
Selenite F-broth does the isolation of Salmonella Typhi from a fecal sample. Selenium allows the growth of desired organisms and, detection levels increase for intestinal flora.
5. Indicator or differential media
This media shows visible changes due to the presence of an indicator. It differentiates bacteria based on colony color growing on the same plate; biochemical characteristics show organism’s growth with chemical indicators like neutral red, phenol red, methylene blue.
Examples of Indicator or differential media
Mannitol salt agar (mannitol fermentation shows yellow color colonies); blood agar is used to differentiate between hemolytic and non-hemolytic. MacConkey agar produces pink colonies due to lactose utilization and, non-lactose shows pale color colonies.
6. Transport media
The media transport specimens after collection to control the overgrowth of organisms. For the cultivation, this media act as temporary storage. It also maintains the viability of pathogens in the specimen and prevents them from drying.
Examples of Transport media
Stuart’s transport medium (lacks carbon, nitrogen, growth factors). Cary Blair’s transport media and VR are used to transport feces samples from cholera patients. Pikes medium helps to transport streptococci from throat patients.
7. Storage media
It maintains the longevity of bacterial culture. Examples are- cooked meat broth, NA egg saline.
Types of culture media based on oxygen requirement
Microorganisms have different requirements for growth depending on oxygen requirements.
1. Aerobic media
In this media, it is easy to cultivate microbes, on solid media, the growth occurs by keeping the culture in the incubator. It shows the growth; of non-fastidious microorganisms.
Examples of aerobic media are- liquid media, solid media
Peptone water- 1%peptone + 0.5% Nacl +100ml water.
Nutrient agar- nutrient broth +2% agar.
2. Anaerobic media
The media cultivates anaerobic bacteria at low oxygen, reducing oxidation-reduction potential. Anaerobic media contains extra nutrients like vitamin K, hemin, and oxygen that get reduced by a physical or chemical process. The addition of glucose (1%), thioglycollate(0.1%), ascorbic acid (0.1%), cysteine (0.05%), or iron fillings added to cause the medium to reduce. The medium is boiled in a water bath to force out dissolved oxygen and packed with sterile paraffin.
Examples of Anaerobic media
RCM (Robertson cooked meat) isolation for Clostridium sp.
Thioglycolate broth– It has sodium glycolate that maintains low oxygen.
Types of special purpose culture media
1. Assay media
The media assay vitamins, amino acids, and antibiotics. Example- Antibiotic sensitivity test the media used is Muller-Hinton agar has 1.7% agar for better diffusion of antibiotics. It also contains starch, which absorbs toxins released by bacteria. In this media plate Zone of inhibition is seen around antibiotics.
2. Minimal media
Principal of minimal media
Minimal media is a defined medium with different compositions depending on microorganisms cultured. It contains a carbon source like sugar/succinate and inorganic salts like magnesium, nitrogen, sulfur, phosphorus. Carbon is a source of energy; magnesium and ammonium salts are the sources of ions for metabolism stimulation. Phosphate is a buffering agent.
The growth comparison of microbe culture and mutant forms- Minimal media and supplementary-minimal media- allow the differentiation of wild-type and mutant cells.
Use- The selection of recombinants, for the growth of wild-type microorganisms.
3. Fermentation media
The media is for optimum microorganisms. Fermentation media produce high yields of the product; media provide energy and nutrients for growth, and medium gives the substrate for the synthesis of products in the fermentation.
Fermentation media contains major and minor components-
Major components – Carbon and nitrogen for energy.
Minor components- This contains inorganic salts, growth factors, vitamins, buffer, anti-foaming agents, dissolved oxygen, gases, growth inhibitors, enzymes.
The nutrients in fermentation media depend on the organism and type of fermentation process.
It has low nutrients and creates raw material for further fermentation.
It has high nutrients and creates end products.
Example- The yeast requires 1% carbon, but the fermentation of alcohol, demands 12-13% carbon in the medium.
Role of fermentation media
The media has a high level of nutrients, microorganisms, and optimum conditions. During the incubation period under optimum conditions, microorganisms undergo metabolism. Fermentation organisms become hyperactive due to nutrients being in high quantities and, the result is nutrients getting consumed, media partially degraded.
The waste effluent is the output product. The death of cells occurs if substrate-level reaches the inhibitory concentration and excess substrate causes them to inhibit vital enzymes. Excess substrate increases osmotic pressure and disturbs enzymatic activity in cells. Microbes release excess substrate as partially digested fermentation media and convert it into the insoluble inert compound as reserve food, which is harmless to cells. Example- yeast extract, beef extract, YPD, BMGY.
Resuscitation culture media
The resuscitation method is for the stressed bacterial recovery; this is a specialized medium that allows the growth of microbes that have lost the ability to produce because of the environmental harness. The culture provides nutrients and recovers their metabolism.
For example- Bacteria require histamine for growth, and the medium lacks this component. Then it inhibits growth. The same bacterium is put in a medium having histamine, then it starts to grow again, and this medium acts as resuscitation media.
For example- Tryptic Soy Agar.
Application of culture media
- To culture microbes.
- To identify the cause of infection.
- To identify characteristics of microorganisms.
- To isolate pure culture.
- To store the culture stock.
- To observe biochemical reactions.
- To test microbial contamination in any sample.
- To check antimicrobial agents and preservatives effect.
- To observe microbe colony type, its color, shape, cause.
- To differentiate between different colonies.
- To create antigens for laboratory use.
- To estimate viable count.
- To test antibiotic sensitivity.
Limitations of culture media
- Risk of cross-contamination.
- High skill required for optimal results.
- Increased drying out of media can occur.
List of Culture media used in Microbiology with their uses
A7 and A8 agars
A7 and A8 agars are selective and differential media used for the cultivation, identification, and differentiation of Ureaplasma spp. and Mycoplasma hominis.
Alkaline peptone water
Alkaline peptone water is an enrichment broth used for the isolation of small numbers of Vibrio and Aeromonas organisms from stool specimens.
American Trudeau Society medium
American Trudeau Society medium is a nonselective enriched medium used for the isolation and cultivation of mycobacteria.
Amies transport medium with and without charcoal
Amies transport medium is a modification of Stuart’s medium. Amies medium with charcoal is preferred for the isolation of Neisseria spp.
Anaerobic blood agar (CDC)
The Centers for Disease Control and Prevention (CDC) formulation of anaerobic blood agar is a general-purpose medium used for the isolation and cultivation of anaerobic bacteria.
10B arginine broth; Shepard’s broth
10B arginine broth is a medium used for the transport and growth of M. hominis and Ureaplasma urealyticum.
Ashdown agar is a selective and differential medium for the isolation of Pseudomonas pseudomallei.
Bacillus cereus medium
B. cereus medium is an enriched medium used for the isolation of B. cereus.
BACTEC 12B radiometric medium
BACTEC 12B medium (BD Biosciences) is a liquid nonselective medium used for the isolation and identification of Mycobacterium species in conjunction with the BACTEC system
Bacteroides bile esculin agar
Bacteroides bile esculin agar is an enriched, selective, and differential medium used for the isolation and presumptive identification of members of the Bacteroides fragilis group and Bilophila wadsworthia.
Baird-Parker agar base
Baird-Parker agar base is an enriched, selective, and differential agar used for the detection of coagulase-positive staphylococci (S. aureus) from food and other non-clinical sources.
Barbour-Stoenner-Kelly medium (Sigma-Aldrich Co., St. Louis, Mo.)
Barbour-Stoenner-Kelly medium is a complicated medium for the isolation of Borrelia burgdorferi.
Bile esculin agar
Bile esculin agar is a selective and differential medium used for the isolation and differentiation of Enterococcus and Streptococcus bovis (group D Streptococcus) from non-group D Streptococcus.
Bile esculin agar plus vancomycin at 6 μg/ml
Bile esculin agar plus vancomycin is a selective and differential medium used to identify vancomycin-resistant streptococci and enterococci.
Bile esculin azide agar and broth (Enterococcosel)
Bile esculin azide agar or broth is a selective and differential medium for S. bovis (group D streptococcus) and enterococci.
Bismuth sulfite agar
Bismuth sulfite agar is a highly selective and differential medium used for the isolation of Salmonella enterica serovar Typhi and other enteric bacilli.
It is the same as Columbia agar with 5% sheep blood.
Blood culture media
All blood culture medium formulations are based on a nutrient peptone broth with variations due to hydrolysis or digestion of the source protein.
Bordet-Gengou medium is an enriched medium used for the isolation and cultivation of Bordetella pertussis from clinical specimens.
Brain heart infusion agar
Brain heart infusion agar is a general-purpose medium used for the isolation of a wide variety of pathogens, including yeasts, molds, and bacteria.
Brain heart infusion agar with 7% horse blood and brain heart infusion agar with 1% serum
Brain heart infusion agar with horse blood or serum enriches the medium for isolation of Helicobacter spp.
Brain heart infusion broth
Brain heart infusion broth is a general-purpose clear liquid medium that is used to cultivate a wide variety of organisms. Formulations with 6.5% NaCl are used for the isolation of salt-tolerant streptococci, formulations with 0.1% agar that reduce O2 tension favor anaerobes, and formulations with Fildes enrichment are used for the isolation of fastidious organisms such as Haemophilus and Neisseria.
Brain heart infusion-vancomycin agar
Brain heart infusion-vancomycin agar is a selective medium used for the isolation of vancomycin-resistant enterococci. The base is brain heart infusion agar. Vancomycin (6g/ml) is added to select for vancomycin-resistant enterococci.
Brilliant green agar
Brilliant green agar is a highly selective and differential medium used for the isolation of Salmonella species except for serovar Typhi.
Brucella agar is a medium designed originally for the purpose of isolating Brucella spp. from dairy products.
Brucella agar with cefoxitin and cycloserine
Brucella agar with cefoxitin and cycloserine is a selective and differential sheep blood medium used for the isolation of Clostridium difficile. Brucella agar is the nutritive base.
Brucella agar with hemin and vitamin K
Brucella agar with hemin and vitamin K is a general-purpose nonselective and enriched medium used for the isolation and cultivation of anaerobic bacteria.
Brucella agar with 5% horse blood
Horse blood enriches brucella agar for fastidious organisms, such as H. pylori, by providing both hemin (factor X) and NAD (factor V) factors.
Brucella Broth is a liquid medium that is used to cultivate Campylobacter species and to identify the organisms to the species level.
Buffered charcoal yeast extract (BCYE)
BCYE is a specialized enriched agar medium used for the isolation and cultivation of Legionella species from environmental and clinical specimens.
Buffered glycerol saline
Buffered glycerol saline is a multipurpose transport medium. The transport medium has been used for the isolation of bacteria, such as Aeromonas spp., as well as viruses. In addition, glycerol-containing media may also be used for long-term storage of isolates and for transport and storage of biopsy specimens.
Burkholderia cepacia selective agar
B. cepacia selective agar is an enriched and selective medium used for the isolation of B. cepacia.
Campylobacter blood agar
Campylobacter blood agar is an enriched selective blood agar medium used for the isolation of Campylobacter species.
Campylobacter charcoal differential (CCD) agar
CCD agar is a blood-free selective medium used for the isolation of Campylobacter from stool specimens.
Campylobacter thioglycolate medium
Campylobacter thioglycolate medium is a selective holding medium used for the isolation of Campylobacter species.
Cary-Blair transport medium
Cary-Blair transport medium was specifically designed to enhance the survival of enteric bacterial pathogens.
Cefoperazone-vancomycin-amphotericin B (CVA) medium
CVA medium is a selective and enriched blood agar medium used for the isolation of Campylobacter species.
Cefsulodin-Irgasan-novobiocin (CIN) medium (Yersinia selective agar)
CIN, or Yersinia selective agar, is a selective and differential medium used for the isolation and differentiation of Yersinia enterocolitica from clinical specimens and food sources.
Cetrimide agar is a selective and differential medium used for the identification of Pseudomonas aeruginosa.
Charcoal selective medium
Charcoal selective medium is an enriched selective medium used for the isolation of Campylobacter species.
Chocolate agar is a general-purpose medium used for the isolation and detection of a wide variety of microorganisms, including fastidious species such as Neisseria and Haemophilus.
Chopped meat glucose broth
Chopped meat glucose broth is an enriched medium that supports the growth of most anaerobes. It is most commonly used to isolate Clostridium botulinum from mixed bacterial growth.
CHROMagar (Rambach agar)
CHROMagar is a microorganism-specific, chromogenic culture medium used for isolation and identification for a variety of organisms. CHROMagar was developed by Alain Rambach, who first formulated agars that were monochromogenic for the detection of E. coli and Salmonella spp. Second-generation agars are multicolor. Both types are differential and selective. The nutritive agar base includes peptone and glucose. Different additives, proprietary chromogenic mixtures, and antibiotics have resulted in a series of media-specific for such organisms as Listeria, S. aureus, methicillin-resistant S. aureus (MRSA), E. coli O157, yeasts, and other organisms.
Columbia agar with 5% sheep blood
Columbia agar with 5% sheep blood is a general-purpose medium used for the isolation of a variety of microorganisms, including fastidious organisms. The addition of 20 gm of ampicillin per ml is helpful in isolation of Aeromonas.
Columbia broth is a general-purpose clear liquid medium used especially for blood culture medium. The broth supports the growth of a wide range of microorganisms.
Columbia-colistin-nalidixic acid agar with 5% sheep blood
Columbia-colistin-nalidixic acid agar with 5% sheep blood is a selective and differential medium commonly used in the isolation of gram-positive aerobic and anaerobic organisms from mixed clinical specimens.
Cycloserine-cefoxitin-fructose agar is a selective and differential agar medium used for the isolation of C. difficile.
Cysteine-albumin broth with 20% glycerol
Cysteine-albumin broth with 20% glycerol is used for the transport and storage of gastric biopsy specimens for the recovery of H. pylori.
Cystine glucose blood agar
Cystine glucose blood agar is an enriched medium used for the isolation of Francisella spp.
Cystine-tellurite blood agar
Cystine-tellurite blood agar is a modification of Tinsdale agar and is both a selective and differential medium used for the detection of C. diphtheriae.
Cystine tryptic agar
Cystine tryptic agar is a pancreatic digest of the casein-enriched medium that is most commonly used for the cultivation and maintenance of fastidious organisms. The addition of 1% carbohydrates and phenol red for the determination of fermentation reactions is especially helpful for differentiating Neisseria spp.
Diagnostic sensitivity agar
Diagnostic sensitivity agar is a medium used in the cultivation of organisms for susceptibility testing.
DNA-toluidine blue agar
DNA-toluidine blue agar is a differential medium used most commonly for the detection and differentiation of Staphylococcus spp.
Dubos Tween-albumin broth
Dubos Tween-albumin broth is a nonselective medium used for the isolation and cultivation of mycobacteria.
Egg yolk agar (modified McClung-Toabe agar)
Egg yolk agar medium (modified McClung-Toabe agar) is a selective and differential medium used for the isolation and differentiation of Clostridium spp.
Ellinghausen-McCullough/Johnson-Harris medium is an enriched semisolid medium used for the isolation and cultivation of Leptospira.
It is similar to Bile esculin azide agar and broth.
Eosin-methylene blue (EMB) agar
EMB agar is a selective and differential medium used for the isolation and differentiation of enteric pathogens from contaminated clinical specimens.
ESP Culture System II
ESP Myco medium is used with ESP Culture System II (TREK Diagnostic Systems) for the detection of mycobacterial growth.
It is similar to the Baird-Parker agar base.
Fastidious anaerobic agar (Fusobacterium selective agar)
Fastidious anaerobic agar is an enriched sheep blood medium used for the isolation and cultivation of anaerobic organisms.
Fletcher’s medium is an enriched semisolid medium used for the isolation and growth of Leptospira.
FlexTrans viral and chlamydia transport medium
FlexTrans viral and chlamydia transport medium (Trinity Biotech) is intended to be used as a transport medium for viruses and/or chlamydiae.
GC agar base
GC agar base is a chocolate agar base used with various additives for the purpose of isolating Neisseria gonorrhoeae and other fastidious organisms, such as Haemophilus spp., including Haemophilus ducreyi, and for susceptibility testing of N. gonorrhoeae.
GN broth is an enriched selective broth medium used for the isolation of gram-negative rods. Specifically, Salmonella and Shigella are isolated more effectively in GN broth than on solid medium alone.
Haemophilus test medium (HTM) and broth
HTM is an enriched medium used for susceptibility testing of Haemophilus species.
Heart infusion agar and broth
Heart infusion agar and broth are general-purpose media used for the isolation of a variety of microorganisms. Incorporation with 5% rabbit blood allows detection of the more fastidious Actinomyces.
Hektoen enteric agar
Hektoen enteric agar is a selective and differential medium used for the isolation and differentiation of enteric pathogens from contaminated clinical specimens. Fermenters such as E. coli produce colonies that are yellow-pink, Shigella spp. is green or transparent, and Salmonella spp. is green or transparent with black centers.
Hemin-supplemented egg yolk agar
It is similar to Neomycin egg yolk agar.
Isolator or lysis-centrifugation tube (Wampole Laboratories)
The Isolator is a unique system for the purpose of recovering organisms from the blood through a simultaneous process of lysis and centrifugation. The system is especially good for the recovery of dimorphic fungi, yeasts, mycobacteria, and Bartonella spp. Recovery of anaerobes, Haemophilus spp., and pneumococci may be reduced.
Iso-Sensitest agar and broth
Iso-Sensitest agar and broth are media used for susceptibility testing in countries outside the United States.
John E. Martin Biological Enrichment Chamber (JEMBEC) (BBL) and InTray GC System transport medium (Biotest)
The JEMBEC and InTray GC devices are transport/inoculation media for direct plating of specimens for the detection of N. gonorrhoeae
Kanamycin-vancomycin laked sheep blood agar
Kanamycin-vancomycin laked sheep blood agar is an enriched, selective, and differential medium used for the isolation and cultivation of anaerobic bacteria, especially slowly growing and fastidious anaerobes from clinical specimens, such as Bacteroides spp. and Prevotella spp.
Lactobacillus MRS broth
Lactobacillus MRS (deMan, Rogosa, and Sharpe) broth is a nonselective liquid medium used for the isolation and cultivation of lactobacilli from clinical specimens and dairy and food products.
Levinthal agar with bacitracin and H. influenzae antiserum
It is similar to Chocolate agar.
Lim broth is a modification of Todd-Hewitt broth and is an enriched selective liquid medium used for the isolation and cultivation of Streptococcus agalactiae.
Lithium chloride-phenylethanolmoxalactam agar
Lithium chloride-phenylethanol-moxalactam agar is an enriched and selective agar used for the isolation and cultivation of Listeria monocytogenes.
Loeffler’s medium is an enriched nonselective medium used for the cultivation of corynebacteria, especially C. diphtheriae.
Lombard-Dowell egg yolk agar
It is similar to Neomycin egg yolk agar.
Lowenstein-Jensen medium is an enriched nonselective medium used for the isolation and cultivation of mycobacteria. It is similar to the American Trudeau Society medium in its content and its ability to grow mycobacteria.
Lowenstein-Jensen medium (Gruft modification)
The Gruft modification of the Lowenstein-Jensen medium is an enriched selective medium used for the isolation of mycobacteria. Penicillin and nalidixic acid are added to the medium and inhibit gram-positive and gram-negative organisms, respectively. RNA is added as a growth stimulant.
Lowenstein-Jensen medium (Mycobactosel modification)
The Mycobactosel modification of the Lowenstein-Jensen medium is an enriched selective medium for the isolation of mycobacteria. Cycloheximide, lincomycin, and nalidixic acid inhibit saprophytic fungi, gram-positive organisms, and gram-negative organisms, respectively. No RNA is added.
Lowenstein-Jensen medium with 1% ferric ammonium citrate
Lowenstein-Jensen medium with 1% ferric ammonium citrate is an enriched and selective egg-based medium used for the recovery of Mycobacterium haemophilum. Ferric ammonium citrate is the additive that allows this organism to grow.
Lowenstein-Jensen medium with 5% NaCl
Lowenstein-Jensen medium with 5% NaCl is an enriched selective medium used to differentiate sodium chloridetolerant strains of Mycobacterium. Most rapid growers, e.g., the Mycobacterium fortuitum complex, as well as the more slowly growing organism Mycobacterium triviale, will grow on this medium.
It is similar to Isolator.
MacConkey agar is a selective and differential medium used for the isolation of gram-negative organisms. The nutritive base includes a variety of peptones. The medium is made selective by the incorporation of bile (although at levels less than those used in other enteric media) and crystal violet, which inhibit gram-positive organisms, especially enterococci and staphylococci.
MacConkey agar with sorbitol (SMAC)
SMAC is a selective and differential medium used for the isolation and differentiation of sorbitol-negative E. coli.
MacConkey broth is a differential medium containing the indicator bromcresol purple used for the detection of coliform organisms from contaminated food, water, or stools.
Mannitol-egg yolk-polymyxin B agar
Mannitol-egg yolk-polymyxin B agar is an enriched, selective, and differential medium used for the isolation of B. cereus from mixed clinical specimens.
Mannitol salt agar
Mannitol salt agar is a selective and differential medium used for the isolation of S. aureus.
Martin-Lewis agar is an enriched and selective medium for the isolation of N. gonorrhoeae.
MB/BacT ALERT (bioMèrieux)
MB/BacT ALERT contains a modified Middlebrook 7H9 medium supplemented with casein, bovine serum albumin, and catalase. It is used with MB/BacT ALERT 3D (bioMerieux, Inc.) for the cultivation and detection of mycobacterial growth.
MGIT (mycobacteria growth indicator tube) (BD Diagnostic Systems)
MGIT is a Middlebrook 7H9-based broth system that contains a fluorescence indicator, which is used for the detection of mycobacterial growth.
Middlebrook 7H10 agar
Middlebrook 7H10 agar is an enriched nonselective agar-based medium used for the isolation and cultivation of mycobacterial species.
Middlebrook 7H11 agar
Middlebrook 7H11 agar is a nonselective agar-based medium used for the isolation and cultivation of Mycobacterium species.
Middlebrook 7H9 broth with glycerol
Middlebrook 7H9 broth with glycerol is an enriched nonselective broth for the isolation of Mycobacterium species.
Mitchison 7H11 selective agar
Mitchison 7H11 selective agar is an enriched selective agar-based medium used for the isolation of Mycobacterium species.
Modified Irgasan-ticarcillin-potassium chromate broth
Modified Irgasan-ticarcillin-potassium chromate broth is a selective broth used for the isolation of Y. enterocolitica.
Modified Thayer-Martin agar
Modified Thayer-Martin agar is an enriched and selective agar for the isolation of pathogenic Neisseria species from clinical specimens with mixed flora.
Mueller-Hinton agar with and without 5% sheep blood
Mueller-Hinton agar with 5% sheep blood is used for susceptibility testing of S. pneumoniae. Mueller-Hinton agar with 5% chocolate blood plus 1% IsoVitaleX and 3gm of vancomycin per ml is used for the isolation of H. ducreyi.
Mueller-Hinton agar with 2% NaCl
Mueller-Hinton agar with 2% NaCl is a selective medium used for testing the susceptibility of Staphylococcus to the penicillinase-resistant penicillins methicillin, nafcillin, and oxacillin by agar dilution or with the gradient-based system (E test).
Mueller-Hinton agar with 4% NaCl and 6 gm of oxacillin per ml
Mueller-Hinton agar with 4% NaCl and 6 gm of oxacillin per ml is the selective, differential medium used to screen S. aureus (not coagulase-negative staphylococci) for resistance to penicillinase-resistant penicillins (e.g., nafcillin, methicillin, and oxacillin).
Mueller-Hinton broth is a magnesium and calcium cation adjusted liquid medium used in procedures for susceptibility testing of aerobic gram-positive and gram-negative organisms by both macro dilution and microdilution methods.
Multiprobe media (M4-3, M5, and M4-RT) (Remel)
M4-3 contains vancomycin, amphotericin B, and colistin and is suitable for the transport of viruses, chlamydiae, Mycoplasma, and Ureaplasma. M5 is similar to M4-3, but it does not contain gelatin. M5 is suitable for the transport of viruses, chlamydiae, Mycoplasma, and Ureaplasma.
Mycobactosel is a BBL trade name for an enriched selective agar-based medium used for the isolation of Mycobacterium species.
MycoTrim GU and MycoTrim RS (Irvine Scientific)
The MycoTrim GU and MycoTrim RS culture systems are unique triphasic flask systems specifically designed for the isolation and identification of M. hominis, U. urealyticum (GU), and Mycoplasma pneumoniae (RS).
NAG medium is an enriched and selective medium used for the isolation and cultivation of Haemophilus species from clinical specimens with mixed flora.
Neomycin egg yolk agar
Neomycin egg yolk agar is a selective and differential medium used for the differentiation of anaerobic organisms that are lipase positive, including Clostridium spp., Prevotella intermedia, Fusobacterium necrophorum, and some strains of Prevotella loescheii.
Neomycin-vancomycin agar is an enriched and selective medium that is particularly good for the isolation and cultivation of Fusobacterium from clinical specimens.
New York City medium
New York City medium is an enriched and selective medium for the isolation of pathogenic Neisseria from clinical specimens.
Nucleic acid transport (NAT) (Medical Packaging Corporation)
NAT is a nucleic acid transport device that is FDA cleared for use with multiple amplification and hybridization testing formats.
Oxford agar is an enriched and selective medium used for the isolation of L. monocytogenes.
Oxidative-fermentative polymyxin B-bacitracinlactose agar
Oxidative-fermentative polymyxin B-bacitracin-lactose medium is a selective and differential medium used for the isolation of B. cepacia from respiratory specimens from patients with cystic fibrosis.
P agar is an enriched medium used for the cultivation and isolation of staphylococci.
Peptone yeast extract broth
Peptone yeast extract broth is used in the analysis of metabolic products by gas-liquid chromatography because there is negligible acid volatility within the medium.
Petragnani medium is an egg-based medium. It is also used for the cultivation and maintenance of Mycobacterium smegmatis.
Phenylethyl alcohol agar
Phenylethyl alcohol agar is an enriched and selective blood agar medium used for the detection and isolation of anaerobic organisms, particularly fastidious and slowly growing bacteria, from clinical specimens with mixed flora.
PLM-5 TM is a proprietary medium formulation (Intergen Co., Purchase, N.Y.) similar to Ellinghausen-McCullough/ Johnson-Harris medium that is used for the isolation and cultivation of Leptospira.
Polymyxin B-acriflavine-lithium chlorideceftazidime-esculin-mannitol (PALCAM) agar
PALCAM agar is an enriched, differential, and selective agar medium used for the isolation of L. monocytogenes.
Polymyxin B-lysozyme-EDTA-thallous acetate agar
Polymyxin B-lysozyme-EDTA-thallous acetate agar is a selective agar used for the isolation of B. anthracis from environmental specimens.
Polymyxin B-pyruvate-egg yolk-mannitolbromthymol blue agar
Polymyxin B-pyruvate-egg yolk-mannitol-bromthymol blue agar is an enriched, selective, and differential medium used for the isolation of B. cereus.
Polysorbate 80 medium
It is similar to Ellinghausen-McCullough/Johnson-Harris medium.
Prereduced anaerobically sterilized (PRAS) media are specifically manufactured (Anaerobe Systems) and packaged to eliminate oxygen to enhance the growth of anaerobic organisms.
Pseudomonas cepacia (PC) agar
PC agar is a selective medium used for the isolation of B. cepacia (formerly Pseudomonas cepacia) from respiratory specimens from cystic fibrosis patients.
It is similar to CHROMagar.
Rappaport-Vassiliadis enrichment broth
Rappaport-Vassiliadis enrichment broth is a selective and enriched broth used for the isolation and cultivation of Salmonella spp. from food and environmental specimens.
Regan-Lowe medium is an enriched and selective medium used for the isolation of B. pertussis. Beef extract pancreatic digest, horse blood, and niacin are the nutritional base.
Salmonella-shigella agar is a selective and differential medium used for the isolation and differentiation of
Salmonella and Shigella from clinical specimens and other sources.
Schaedler’s agar is a general-purpose medium used for the isolation and cultivation of anaerobic bacteria.
Schleifer-Kramer agar is a selective medium used for the isolation of Staphylococcus from heavily contaminated specimens such as feces.
Selenite broth is an enrichment broth medium used for the isolation of Salmonella and Shigella species.
Sensitest agar is a medium used in susceptibility testing outside of the United States.
Septic-Chek biphasic mycobacterial media
The Septic-Chek system (Becton Dickinson Microbiology Systems) is a mycobacterial culture system that contains modified 7H9 broth and three types of solid media, modified Lowenstein-Jensen, Middlebrook 7H11, and chocolate agars, with various supplements.
Skirrow medium is an enriched selective blood agar medium used for the isolation of Campylobacter spp. from specimens with mixed flora.
STGG medium (skim milk, tryptone, glucose, and glycerin) is a transport medium that has been used for the collection of nasopharyngeal swabs for the purposes of isolation and preservation of S. pneumoniae.
StrepB carrot broth kit (Hardy Diagnostics) and GBS broth (Northeast Laboratory Services)
Carrot broth and GBS broth are media that allow for the detection of red, red-orange, or orange pigment production by beta-hemolytic S. agalactiae (GBS) due to the hemolytic reaction with substrates such as starch, protease, peptone, and serum.
Streptococcus selective agar
Streptococcus selective agar is a selective medium for the detection of streptococci. The agar base is Columbia agar.
Stuart’s transport media with and without charcoal
Stuart’s transport medium is an early transport medium first described in 1948. This medium uses glycerol phosphate to maintain the specimen as well as maintain the pH, agar, methylene blue as a redox indicator, and sodium thioglycolate to allow the survival of anaerobes.
Sucrose-phosphate-glutamate transport medium
Sucrose-phosphate-glutamate transport medium is used for the maintenance and transport of Chlamydia species and viruses.
2-Sucrose-phosphate transport media
2-Sucrose-phosphate medium is used for the transport of specimens for the purpose of culturing Chlamydia trachomatis and Mycoplasma spp.
Tetrathionate broth base
Tetrathionate broth base is an enriched liquid medium used for the isolation of Salmonella species in contaminated clinical specimens and other products.
Thayer-Martin agar is an enriched and selective medium used for the isolation of Neisseria from clinical specimens with mixed flora.
Thioglycolate with hemin and vitamin K
Thioglycolate broth with hemin and vitamin K is an enriched liquid medium used to support the growth of
microaerophilic and anaerobic organisms, including fastidious organisms.
Thiosulfate citrate bile salt sucrose (TCBS)
TCBS is a highly selective and differential medium for the recovery of Vibrio spp. except for Vibrio hollisae and Vibrio cincinnatiensis.
It is similar to Cystine-tellurite blood agar.
Todd-Hewitt broth with gentamicin and nalidixic acid
Todd-Hewitt broth is used for the isolation of beta-hemolytic streptococci from mixed flora, especially vaginal specimens for GBS.
Tryptic or Trypticase soy agar base with 5% sheep blood
Tryptic or Trypticase soy agar base with 5% sheep blood is a general-purpose medium used for the isolation of a wide variety of organisms. The use of sheep blood provides an excellent means of interpretation of hemolytic reactions, especially those of Streptococcus spp.
Tryptic or Trypticase soy broth
Tryptic or Trypticase soy broth is a general-purpose clear liquid medium used for the cultivation of a wide variety of organisms. It is also recommended by the CLSI for the preparation of inoculum for Kirby-Bauer disk diffusion susceptibility testing and is the CLSI’s choice as a sterility testing medium. Formulations with 6.5% NaCl exist for the purposes of differentiating enterococcal species or salt-tolerant streptococci. Fildes enrichment is added to cultivate fastidious organisms such as Haemophilus spp.
Trypticase soy agar with horse or rabbit blood
Trypticase soy agar with horse or rabbit blood medium is used for the isolation of Haemophilus species.
University of Vermont modified listeria enrichment broth
University of Vermont modified listeria enrichment broth is an enriched and selective liquid medium used for the isolation of L. monocytogenes.
V agar is an enriched and selective medium used for the isolation of G. vaginalis from clinical specimens.
VMGA III medium
VMGA III (viability medium, Goteborg, anaerobic) is a transport and collection medium specifically designed to maintain the viability of mixed anaerobes from peridontal and endodontal sites.
It is similar to Buffered charcoal yeast extract (BCYE).
Wilkins-Chalgren broth and agar
Wilkins-Chalgren medium is recommended for susceptibility testing with anaerobic organisms. The medium contains specific nutrients that support the growth of anaerobes such as yeast extract, vitamin K, hemin, and arginine.
Xylose-lysine-desoxycholate (XLD) agar
Xylose-lysine-desoxycholate agar is a selective and differential medium used for the isolation and differentiation of enteric pathogens from clinical specimens. This medium is more supportive of fastidious enteric organisms such as Shigella. For Salmonella, which contains the lysine enzyme, this reaction reverts the pH to an alkaline state and the colony appears to be transparent or red with a black center. A number of other similar media for isolation of enteric pathogens exist, including xylose-galactosidase medium, which is more specific for Aeromonas spp.
Yersinia selective agar
It is similar to Cefsulodin-Irgasan-novobiocin medium.