CHROMagar: Chromogenic powdered media, if you think there's a plate for it, there is

Good morning! Welcome back, I hope you had a nice easter break and everything went accordingly (If you planned anything). This week we're talking about CHROMagar Microbiology, you've probably heard of them, and more than likely used their chromogenic media at some point, if you've ever stepped foot into a microbiology lab.
For the un-initiated, I will include a bit of information about what chromogenic media is and why it's neat so don't worry if you've never heard of a CHROMagar!
What we're talking about today is a little different to how you might know CHROMagar, as we instead deal with their plates in powder form! Now you may think this is pretty old-school, BUT!, there are benefits to dehydrated media compared to your usual fridge-stored plates.

---

What are chromogenic media plates?

We're going all the way back to basics for this one so bear with.

Chromogenic materials are defined as substances that exhibit a reversible change in coloration, in response to external stimuli. Chromogenic media contains chromogens, consisting of a substrate and a chromophore. Plates, before use are colourless because the chromophore does not absorb visible light whilst conjugated to the substrate [1].

When a specific bacterial organisms enzymatic activity comes into contact with the chromogen molecule, that enzyme cleaves the chromogen molecule which releases the chromophore, as this chromophore is no longer conjugated, the light becomes visible [1].

The chromophore used does not diffuse readily into the surrounding media, meaning that the colour stays concentrated in the area specifically where the bacterial colony with the target enzymatic activity grew. This is why the colony itself takes on the chromophores colour [1].

Chromogenic media utilise synthetic chromogenic enzyme substrates in order to specifically target pathogenic species, based on their enzyme activity. This enzyme activity is never completely species-specific, requiring the use of complementary enzyme substrates and/ or selective agents. This means that the majority of chromogenic media are both selective and differential as they accommodate the inhibition of non-target organisms whilst enabling target pathogens to grow as coloured colonies due to their metabolism, which is usually through hydrolysis, of one or more chromogenic enzyme substrates [2].
​
[1] https://asm.org/articles/2020/september/how-chromagar-tm-revolutionized-bacterial-identifi
[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC5355637/

---

What CHROMagar plates are there?

Glad you didn't ask! I made you a long table of every plate, the size they come in, and if they come with a supplement or not. The product codes are our product codes btw not CHROMagar's even though they are almost identical :)

For more information on each specific product, and to speak with us about these chromogenic plates, visit our CHROMagar website at: https://www.bioconnections.co.uk/chromagar-home.html.

---

Cherry Picking

I would like to highlight to you some of the media that we feel are worth your time. Most of these products can also be found on our drug-resistant bacteria detection page on our website, and the clinical microbiology section on CHROMagar's website.

CHROMagar ESBL

Intended for use in the qualitative direct detection of gastrointestinal colonisation with Extended-spectrum-beta-lactamase-resistant Enterobacteria (ESBL), to aid in the prevention and control of ESBL in healthcare settings. Plates can be inoculated with rectal swabs and stool samples from patients to screen for ESBL colonisation, with results viable for interpretation 18-24h of aerobic incubation at 35-37°C.

CHROMagar mSuperCARBA

Intended for the use in the qualitative direct detection of gastrointestinal colonisation with carbapenem-resistant Enterobacteria (CRE), including OXA-48 producers, to aid in the prevention and control of CRE in healthcare settings. This medium can also be inoculated with rectal swabs and stool samples from patients to screen for CRE colonisation, with results viable for interpretation after 18-24h of aerobic incubation at 35-37°C.

CHROMagar MRSA

Intended for the use in the qualitative direct detection of colonisation by methicillin resistant Staphylococcus aureus (MRSA) to aid in the prevention and control of MRSA in healthcare settings. This media can be inoculated with anterior nares or perineal swabs from patients, and healthcare workers, to screen for MRSA colonisation. With results viable to interpret after 18-24h of aerobic incubation at 35-37°C.

CHROMagar Acinetobacter

Intended for use in the qualitative direct detection of colonisation with Acinetobacter to aid in the prevention and control of Acinetobacter, drug-susceptible or multi-drug resistant (MDR), in healthcare settings. This media can be inoculated with rectal swabs, nare swabs, wound swabs, stool and urine samples from patients to screen for Acinetobacter colonisation. Furthermore, it can also be used in hygiene monitoring in clinical environments with surface sampling. Results are viable for interpretation after 18-24h aerobic incubation at 35-37°C.

CHROMagar COL-APSE

Intended for use in the qualitative direct detection of gastrointestinal colonisation with colistin-resistant Gram-negative bacteria (COL-R) to aid in the prevention and control of COL-R in healthcare settings. This media can be inoculated with rectal and perineal swabs, and stool samples from patients to screen for COL-R colonisation. Results are viable for interpretation after 18-24h of aerobic incubation at 35-37°C.

CHROMagar LIN-R

Intended for the use in the detection, isolation and differentiation of strains of Staphylococcus and Enterococcus resistant to linezolid. Although prevalence of linezolid resistance remains low, the emergence of LIN-R strains is still a great concern. Linezolid sensitivity in gram positive clinical specimens is primarily monitored by surveillance programs in Europe, and in the United States. Clinical isolated for surveillance of LIN-R strains include swabs from the nose (screening for Staphylococcus), perianal and rectal areas (screening for Enterococcus).

---

The power of powder

I would like to reiterate my earlier point about how all of these media are available through BioConnections, but as dehydrated media. Which means we ship the media like this ⬇️⬇️

This is the only format we ship out CHROMagar plates, as dehydrated media. Now, to some of you, this may seem rather old-school, to have to pour your own plates. However there are some benefits to dehydrated media that you may have missed:

• Dehydrated media has a much longer shelf-life, instead of a month or two (I think that's the norm for pre-poured media) this stuff LASTS, you can see in the above photo, this bottle of CHROMagar mSuperCARBA does't expire for YEARS.
• So, these bottles are from 5L to 25L, and with 5L (pouring at 20mL per plate) that will make somewhere in the range of 250 plates. Which is quite a lot for how much space it takes up (not as much as your box of 200 plates that needs to go in the fridge).

Now, I am not saying dehydrated media is better than pre-poured plates, as it just isn't as convenient as grabbing the plates out the fridge when you need them. But think of the times where you have to bin expired media that just didn't get used. Especially with the lesser-used highly selective (expensive) media, with dehydrated media, you could always have it in stock, and you could make up only what you need when you need it, reducing waste and lost money.
Okay I'm done talking now, you can check out CHROmagar if you want! I think they're pretty neat.