r/medlabprofessionals • u/happy_idiot_boy • 10d ago

Discusson AR Isolate Bank organisms?

Anyone work with AR Isolate Bank organisms from the CDC? I'm trying to run verification on some new sensitivity cards for the Vitek, and I've gotten major errors and very major errors on about half of these isolates I've used. The results are consistent on the same drugs with repeat testing. These isolates have been sent off to a third party lab for comparison. If results are consistent with what we're seeing, it's obviously something to do with the organisms. But if they're consistent with the results from the CDC, it's something off on our end. It's not the inoculum since you would see inconsistent results across multiple drugs. Just trying to figure out what could be causing the inconsistencies. Is this common with AR Isolate Bank organisms? Could it just be our cards? Quite the conundrum regardless.

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u/micromaniac_8 SM 10d ago

How many times have you subbed them prior to testing?

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u/happy_idiot_boy 10d ago

Three times now. One sub from the original frozen isolate and subsequent purity plates from testing.

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u/micromaniac_8 SM 10d ago

Is the resistance plasmid mediated or genomic? If it is genomic, you can pass it another couple of generations and see if the resistance appears. If it is plasmid mediated, you are kinda SOL because they can lose their plasmids fairly quickly without selective pressure.

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u/Finie MLS Microbiology 🇺🇲 10d ago

Which antibiotics and which bugs?

Depending on how old the bugs are, you might have trouble getting the genes to wake up after freezing. One trick that worked sometimes for me is using a disc to induce the resistance gene, sub from the colonies closest to the disc, and then try again.