Dehydrated Culture Media FAQs

a.   Dehydrated culture media are composed of various raw materials such as:
b.   Peptones as nitrogen source
c.   Carbohydrates as carbon source
d.   Minerals (Metals and inorganic salts)\
e.   Selective agents
f.   Vitamins
g.   Dyes and pH indicators
h.   Solidifying agent
1.   Some organisms utilize a very wide range of carbohydrates while others are much more selective or have definite preference to certain carbohydrates. These latter organisms can be identified by their fermentative or oxidative assimilation of test carbohydrates added to the medium. A large number of media formulations in which specific carbohydrates and an indicator are included to detect the specific enzyme reactions are particularly adopted in diagnostic bacteriology.

2.   Carbohydrates used in culture media are tested to ensure their identity and purity from adulterants. Growth supportive properties of carbohydrates are tested by preparing liquid and solid culture media along with known standard carbohydrates. On solid media, colony characteristics on reference and test carbohydrate media are compared after sufficient incubation period for size, colour, shape and enzyme reaction with indicators.

Some inorganic mineral salts are essential for the growth and metabolism of all living cells. Most bacterial requirements are met by the addition of sodium, potassium, magnesium, manganese, ferrous or ferric ions in the form of their chlorides, phosphates and sulphates to the culture media.
Bile derivatives are selective agents used to differentiate between those bacteria which have the capacity to survive in the gut and those which cannot live in that environment. By increasing the concentration of bile or bile derivative(s), selective media are prepared for bacteria which are differentiated on the basis of bile tolerance.
Bile Salts are analysed chemically as described in National Formulary for Sodium deoxycholate, Sodium cholate and Sodium taurocholate. Following criteria are used for passing bile salts. When bile salts are incorporated into Culture Media they should not affect the colour of the indicator dye(s) or their subsequent change in colour as desired in the medium. It should not form a surface scum or deposit in the medium after storage. Further, bile functional test is carried out, using standard bile salts as controls. Also recovery test of bacteria is carried out with E. coli as one of the test organism when a bile salt of known performance is used as a control. Solid media prepared with different bile salts are tested by the Miles-Misra surface drop test. The growth recovery of various Enterobacteriaceae is recorded for each medium
The degradation products of protein hydrolysis, commonly called peptones, are mixtures of polypeptides, oligopeptides, amino acids, organic nitrogen bases, salts and trace elements. The variety of peptones produced reflects the differing demands of microorganisms for amino acids and peptides. The characteristic of the peptone changes depending on the protein substrate (casein, meat or soya) and the type of hydrolysis, enzyme (trypsin, pepsin or papain) hydrolysis or acid hydrolysis.
Yes, Beside HiMedia’s own specifications, in general, peptones are analyzed as specified in USP under the title ‘‘Peptic Digest of Animal Tissue’’, similar criteria for ‘‘Pancreatic Digest of Casein’’.
In HiMedia, we believe that customer deserves the best quality. We feel responsible for giving our valued customers the best service at an affordable price. We cater to the massive needs of big industrial set-ups like the fermentation pharma sector as well as to the smallest labs and various educational institutions.
At HiMedia, we have made ‘Quality’ possible by maintaining consistent Quality systems in the Design as well as Production phase. Further to enhance production facilities since last 3 years we have introduced WHO GMP at every stage to ensure “Quality” of products manufactured. Our motto “in the service of mankind” has remained the same since our establishment in 1976.
HiVegTM peptones are peptones of plant origin. These are acid or enzymatic hydrolysates of proteins of plant origin. They have similar characteristics to that of animal peptones.
Hi Media offers a very broad range of media formulations; standard media and customer specified media in dehydrated form for use in different fields; clinical , food, environment, cosmetic, dairy, water, pharmaceutical industries etc. This also includes media specified by various pharmacopoeias recommended for different applications as sterility testing, microbial limit tests etc.
The design of Microbiological Culture Media requires statistical evaluation of each ingredient and measurement of the interaction of each ingredient with the other. Awareness of this is of vital importance and accordingly various quality control measures are adopted by HiMedia prior to and during the manufacturing processes so that; desired end products with predictable reproducible results are obtained.
Only the highest quality raw materials are used in the making of HiMedia products. The raw materials are bought only from approved vendors who meet all the acceptance standards. Each raw material is analyzed for grade, quality and purity as per the standards specified in various pharmacopoeia. For the raw materials and chemicals whose standards are not specified, we have our own in-house standards set by our quality assurance department.
Dyes added to culture media also function as selective agents or as pH or Eh indicators. When used as selective agents, interaction may occur between dye and other components in the formulation. Thus, the same sample of brilliant green may show different inhibition titers against E.coli when tested in different Peptone solutions. Bile Salts interact with brilliant green and reduce the toxicity of the dye and therefore toxic level of such dyes is ascertained by adding to Bile Salts Medium. Aniline dyes are more toxic when fully oxidized and therefore a change in its toxicity is possible as reduction of the dye takes place when it is sterilized in the presence of Peptone or Tryptone. Also if Agar used in culture media is high in minerals, incompatibility with the Media constituents may occur.
Therefore, we analyze the dyes used in our culture media as specified by H.J. Conn’s. Besides ascertaining chemical purity of dyes, microbiological suitability is carried out by adding dyes in Culture Media. These are then tested with various test organisms and compared with standard known dyes.
The primary purpose of agar in culture media is to form a solid gel. The clarity of agar gel in culture media is an important characteristic. Ideally, the molten solution should be crystal clear without any haziness or deposit. Haziness in agar is due to mineral incompatibilities or minute fragments of debris which have passed through the filters during manufacturing. Another characteristic of agar is its ability to allow diffusion of compounds while locking water into a rigid gel. This property is exploited in microbiological assay of certain vitamins and antibiotics. Here the diffusion from a central reservoir of antibiotic results in proportionate killing of the test organism while in the case of vitamins yields proportionate zone of growth referred to as zone of exhibition.
Various chemical impurities are analyzed while testing agar for bacteriological purpose. Besides above tests, toxicity test is carried out to ascertain the presence of toxic and inhibitory substances. This is done by growing fastidious organisms on culture media where agar is incorporated and the growth, colony size, shape, pigments, etc. are compared with known standard agar.
HiCromeTM, a range of culture media have chromogenic substances as an ingredient. It is often added as mixture of two chromogens. The chromogens serve as substrate that is cleaved by specific enzymes produced by growing bacteria and / or fungi. The resulting chromophores colours the colony that can be differentiated on basis of different colour reaction. For example: X-glucoronide is cleaved by the enzyme-glucoronidase produced by E. coli strains to yield glucuronic acid, which imparts a bluish green coloration to the colonies of E. coli.

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