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.
Selenite Broth was invented by Leifson who proved that selenite is inhibitory to bacteria, coliforms, and other species, like streptococci from feces, which are found in fecal samples and, consequently, beneficial in the recuperation from Salmonella species. Selenite-F Broth is utilized to enrich the environment that is buffered by Lactose Peptone Broth to which Sodium Biselenite is added to act as the agent that is selective for elimination of Salmonella from urine, feces and water, as well as food items and other substances that are of sanitary significance.
In 1984, Bolton et al. Bolton et al. (1984) suggested that charcoal could be used to replace blood in a medium for the isolation of Campylobacter species. Endtz et al. Later, it was confirmed that Campylobacter isolates at a higher rate when using charcoal selective media.
Amies Transport Medium, which contains charcoal to increase the viability and longevity of pathogenic organisms, is an improved transport medium. It is semisolid media that can be used in qualitative procedures to transport clinical swab specimens from the hospital to the laboratory. This modified Stuart’s Transport Medium is made by adding charcoal to the medium and replacing the glycerophosphate. This modified medium produced a higher percentage positive results than Stuart’s transport medium.
Thioglycolate broth, an enrichment broth that is multipurpose and can be used to determine the oxygen needs of microorganisms, is called a differential medium. It is used most often in diagnostic bacteriology as an enrichment broth. This broth is supportive of the growth and development of microorganisms fastidious, anaerophilic, microaerophilic and aerobes.
In 1978, Feeley et al developed a medium for isolating Legionella species. They later modified it by replacing casein hydrolysate with beef extract and starch with activated carbon and naming it Charcoal Yeast extract (CYE) Agar. A further modification was made by Pasculle et al in 1980 by the addition of ACES (N-2-acetamido-2-aminoethane sulfonic acid) buffer in order to maintain the proper pH for optimal growth designated as BCYE for Buffered Charcoal Yeast Extract. Edelstein et al modified the medium in 1981 by adding potassium salt to alpha-ketoglutaric acids, which increased the medium’s sensitivity. It is used in primary isolation and cultivation of Legionella species. It is recommended to be used in the cultivation and primary isolation of Legionella spp.
Cetrimide, a quaternary salt of ammonium, acts as a detergent that lowers the surface tension at the point-of-contact. It also has precipitant, complexing, and denaturing effects upon bacterial membrane proteins. It has inhibitory properties on many microorganisms, including Pseudomonas species that are not Pseudomonas. Lowburry was the first to develop cetrimide agar. It is a modified version of Tech Agar (developed in King et al. For the selective inhibition other than Pseudomonas, aeruginosa, 0.1% cetrimide (cetyltrimethyl ammonium bromide), was added. Cetrimide agar can be used to presumptive identify and selectively isolate Pseudomonas.aeruginosa species from both clinical and nonclinical specimens.
Over the years, many media have been developed for mycobacteria cultivation. Early ones included egg-based formulations such as Lowenstein-Jensen Medium or Petragnani Medium. Later, Dubos, Middlebrook and Middlebrook created a variety of formulations that contained oleic and albumin as key components. These ingredients protect Mycobacterium against toxic agents and allow for the growth and development of tubercle bacteriailli. Cohn and Middlebrook improved the formulations of oleic acids-albumin agar to achieve a faster and more luxurious growth of Mycobacterium strains.
Endo created Endo Agar to distinguish gram-negative bacteria based on lactose fermentation and inhibit gram-positive bacteria. The latter were not inhibited by bile salts, as was traditional. Endo was able to inhibit gram-positive bacteria using sodium sulfite, basic fuchsin.
Salmonellae are the most complex taxonomically diverse group of bacteria in Enterobacteriaceae. Salmonella infections in humans are usually caused by the consumption of food, milk, and water contaminated with animal or human excreta. S. Typhi is only found in humans.
Egg Yolk Agar modified is based upon the original Egg Yolk Agar formula developed by McClung & Toabe to isolate and differentiate organisms based in Lecithinase, lipase production, and proteolytic activities.
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