Because chromogenic medium are very costly . various company are manufacturing a list of chromogenic media for their respective organisms.
but we can also apply selective media for the detection of a particular microorganism
Chromogenic substrates have proved to be a powerful tool in the
identification of microorganisms due to the detection of specific
enzymes produced by the target microorganism. These enzymes
cleave the chromogenic substrate that points up the
microorganism by color differentiation of the grown bacterial
colonies.
• Enhanced accuracy and easy microbial detection and identification
by means of color.
• Cost efficient working process.
• Time lag reduction, faster bacterial identification and results.
Chromogenic media are available as dehydrated media or in
ready-to-use formats
Both possitions are valid, because only when you need detect fast the particular microorganism is more easy use the chromogenic media; but if you don't need know "today" wath organism is you can apply the basic techniques like as the selective media
Chromogenic media could be in some cases more selective in that you would associate the colour with the microorganism but this is not always the case and you can still get false positives and you still need further confirmatory tests such as molecular or biochemical tests. You must be careful when you talk about selectivity, many media are only partly oe semi-selective not 100%.
i agree with Yvan Moutia chromogenic media some times give false positives but it will help full 2 rapid detection of organisms which are showing similar bio chemical reactions... and mimicking with other organisms... but don't relay 100% chromogenic media. only the advantage is each organism associate with a special color.... and have 2 confirm the organism by all the bio-chemical tests.
@Shashank.
Just to add to what has been said earlier. A selective medium basically is to shortlist your candidates (bacteria) of interest from a heterogenous crowd. depending on the nature of selection you may be able to be highly choosy or else you may get a handful of bacteria you need to do further characterization to get their true identity. A chromogenic medium per se is to identify specific type/ strain of a bacteria/ yeast for eg Chromogenic medium for Candida (CHROMagar) has been shown by many workers to be useful in specifically identifying 4 or 5 different Candida species viz. albicans, dubliniensis, tropicalis, glabrata, krusei. . The advantage of a chromogenic medium is that you can use it for screening a clinical specimen directly or use for confirming an isolate from a primary culture plate. so it would advantageous to pick out a colony of interest based on the colour they would characteristicaly exhibit but this may also depend on the one who would be reading it . There are now Chromogenic agar to identify drug resistant bacteria for eg. MRSA. also note that the composition is very much proprietary (the chromogenic ingredient!).
yes i agree with C.P.Girish Kumar before that u have 2 choose the specific chrome media based on the clinical specimen which are available in the market... ex. for urine isolates u can use urichrome.. and othe and fungal chrome agar having special media but i dont know is their any special media is available or not for body fluids.. before processing u have to keep controls with known organism to know the quality..part because the chrome agar have short life span...
Chromogenic substrates have proved to be a powerful tool in the
identification of microorganisms due to the detection of specific
enzymes produced by the target microorganism. These enzymes
cleave the chromogenic substrate that points up the
microorganism by color differentiation of the grown bacterial
colonies.
• Enhanced accuracy and easy microbial detection and identification
by means of color.
• Cost efficient working process.
• Time lag reduction, faster bacterial identification and results.
Chromogenic media are available as dehydrated media or in
ready-to-use formats
Selective media is to isolate a specific organism from a group/colony.
For faster differentiation of the microbe eg:enterobacteriaceae, the chromogenic media is helpful.
Becuase each organism is identified with specific colour.
For entercocci the bilesceulin is very good as selective media and my supervisor on my reserach ask to add chromogenic media what is the advantage? I feel more coast only
cI thank Mr.Avinash. The advantage is in a single medium u can identify more than one organism, though it is cost.
And more-over in cost wise, if we take one each specific media for more than one organism, the chromogenic media is cheaper.
yes i agree with Leela Nath, chromogenic media is more useful when mixed growth of bacteria is isolated, it reduces time, cost effect in mixed growth as well as to confirm the priority of the pathogenic organism (in mixed cultures may get more than one type of organisms could be Gram positive or Gram Negative), and no need to go for selective media. But these are useful when Quality and stability is good only.
Please correct if I am wrong.
Regards,
Ashok
What I found is "Chromogenic Culture media is media for the simple and fast detection of bacteria using chromogenic substrates. The chromogenic mixture contains chromogenic substrates as Salmon-GAL, X-Gal, X-glucuronide, etc. Certain enzymes, produced by some bacteria, cleave these substrates, resulting in the different coloration of certain bacteria colonies."
Chromogenic media helps in identifing upto species level as in case of candida where some species show same biochemical test like that of sugar fermentation and assimilation so in that case it helps.
so, in a media we can add single chromogen or chromogrnic mixture as per requirement. is chromogenic mixture readily available or we have to formulate it using the required chromogen, since someone mentioned it is company's proprietary. can any one suggest reference or read material on this chromogenic mixture?
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