Culture media are substances used to grow and maintain microorganisms in the laboratory. They typically consist of a mixture of nutrients and other substances that support the growth and metabolism of microorganisms. Culture media can be liquid, semisolid, or solid, and they can be tailored to the specific requirements of different types of microorganisms.
Culture media are an important tool in microbiology, as they allow scientists to isolate, identify, and study microorganisms in the laboratory. They are used in a wide range of applications, including the identification of pathogens, the production of biotechnology products, and the study of the biology and behavior of microorganisms.
There are many different types of culture media, including:
Nutrient media: These media contain a variety of nutrients, such as carbohydrates, proteins, and minerals, to support the growth of microorganisms.
Selective media: These media contain specific substances that inhibit the growth of certain types of microorganisms, allowing only certain types of organisms to grow.
Differential media: These media contain substances that allow different types of microorganisms to be distinguished based on their growth characteristics.
Enrichment media: These media contain substances that enhance the growth of certain types of microorganisms.
Culture media are an essential tool in microbiology and are used in a wide range of research and applied settings. They allow scientists to study the biology, behavior, and ecology of microorganisms and to identify and characterize new species. They also play a crucial role in the production of biotechnology products and in the diagnosis and treatment of diseases caused by microorganisms.
As a primary plating medium, Brilliant Green Agar medium should be used to isolate Salmonella species. Kristensen and colleagues first described it as a selective isolation medium to Salmonella species. Kristensen et al. first described it as a selective isolation medium for Salmonella species. Kauffmann modified the formula to make it a highly selective plating media for the isolation and identification from salmonellae in feces, other pathological material, food and dairy products. Brilliant Green Agar should always be used in conjunction with other selective plating media like Deoxycholate Citrate Agar and Hektoen Enteric Agar. Salmonella Typhi is treated with Bismuth Sulphite.
Hektoen Enteric Agar, a selective and differential medium, is used to distinguish Salmonella and Shigella species from other Enterobacteriaceae. Sylvia King, William I. Metzger introduced the medium in 1968. They developed HE Agar medium during their time at the Hektoen Institute, Chicago, in order to improve the recovery of Salmonella and Shigella from clinical specimens.
Schiemann first described Yersinia selective agar as an alternative to MacConkey agar and other media commonly used for isolating Yersinia Enterocolitica, a causative organism of gastroenteritis. Yersinia Enterocolitica, a major food- or waterborne enteric pathogen, has been reported to cause epizootic outbreaks in animals such as diarrhea, lymphadenopathy and pneumonia. Yersinia Selective Agar, a selective and differentiated medium that supports the growth of Y. Enterocolitica and other Yersinia spp.
Cystine-Lactose-Electrolyte-Deficient (CLED) medium, first described by Sandys and later modified by Mackey and Sandys, is generally used for diagnostic routine urinary bacteriology as a non-selective medium capable of supporting the growth of most urinary pathogens. CLED Agar, a differential medium for the isolation and counting of bacteria from urine, is used. It supports the growth all potential urinary pathogens. The medium also provides distinct colony morphology. It is suitable for the growth of all urinary pathogens, contaminants, and provides good colonial differentiation. However, it does not allow for the spread of Proteus species because of its low electrolytes.
Thiosulfate-citrate-bile salts-sucrose (TCBS) Agar, is a type of selective agar that is used in microbiology laboratories to isolate Vibrio species. TCBS Agar can be used to cultivate Vibrio cholerae from clinical specimens or other materials. Kobayashi et. al. developed TCBS Agar, which modified the Nakanishi selective medium. This medium was originally intended to isolate V. cholerae from V. parahaemolyticus. However, Vibrios can grow healthy colonies with many different colonial morphologies.
Anaerobic blood agar is a solid media that can be used in qualitative methods for the isolation and cultivation anaerobic organisms. V.R. Dowell and T.M. Hawkins, Centers for Disease Control and Prevention Atlanta, Georgia. Anaerobic blood agar supports the growth of anaerobes with typical pigmentation, both fastidious and slow-growing, and other anaerobes that are of clinical significance.
Czapek medium (also known as Czapek’s agar or Czapek Dox medium) is a medium used to grow fungi and other organisms. This medium is suitable for qualitative cultivation of soil bacteria and saprophytic fungi. Czapek originally created the medium in 1902 to cultivate saprophytic mushrooms. Czapek-Dox Agar, a modified formula of the Czapek (1902-1903) and Dox (1910) formulas, is prepared according to Thom & Church. Medium contains sucrose as the only source of carbon, and nitrate is the only inorganic nitrogen source.
PCA, also known as plate count (PCA) is an bacteriological medium that is used to determine the total amount of aerobic live bacteria present in a sample. This is not considered to be a specific medium. The quantity of bacteria is expressed in units of colony-forming units per Gram (CFU/g) in solid samples, and per milliliter (CFU/ml) for liquid samples. The preferred method is to use the pour plate method. The samples are dilute and the appropriate dilutions added to Petri plates. Sterile molten Agar is added to the plates. The plates are rotated with care to ensure an even mixing of the sample with the agar. The plates are then incubated at 20 or 30degC over three days. After incubation, the amount of colonies counted is recorded on the plate using 25-250 colonies, which is believed to provide the most precise results. When calculating the amount of bacteria present within the specimen, the dilution factors is to be considered.
The most meticulous organisms that have a high nutritional requirements can be developed using infusion media. Meat infusions were among the first media utilized to cultivate bacteria. Huntoon created a medium with fresh beef heart and peptone that was later named the Heart Infusion Aggar. He showed that it can be utilized to help support the growth of fastidious nutritional microorganisms, without the need for enrichment like blood from animals. Heart Infusion Agar can be used as a general-purpose growth medium. It is recommended for cultivation of fastidious and nutritious microorganisms and as a medium for basal growth that can be used for a wide range of purposes.
Cystine Glucose blood agar is also known as Cystine Heart Agar. Francis developed blood-dextrose-cystine agar after determining F. tularensis would only grow on an artificial medium supplemented with sulfhydryl compounds (i.e., cystine). F. Tularensis is extremely meticulous organism that requires cystine to grow at its best. To honor the achievements of all time of Francis in the field of understanding the disease it was named Francisella Tularensis. The hemoglobin-rich medium is suggested to cultivate Francisella Tularensis. Without enrichment supplies, it facilitates the growth of cocci gram-negative and other pathogenic organisms.
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