Salvaging Microbiology Cultures

         A dreaded statement to make on a culture report is specimen lost due to laboratory accident. This is a fancy way to say that we screwed up. Depending on the specimen type, the lab could open itself up for heaps of trouble. At best, clinicians and patients get annoyed. At worst, there could be legal implications or deaths. Thankfully, things have never gotten as bad as the latter throughout my career.

         How do you salvage a culture when you could no longer find the corresponding agar plates? After all, accidents and oversights do happen from time to time. It's part of being human.

When patient sample is still available

         The easiest way to resolve it is to resetup the entire culture from cached patient specimen. It's not unusual to keep most patient samples (other than urine and blood) for about a week. The downside to this approach is that we delay the results. This usually means anywhere from 36-72 hours, or more, depending on the complexity.

When patient sample is no longer available

         Sometimes, the original specimen is no longer around. This has more to do with how long we keep patient samples per protocol. Yes, different sample types have different shelf life. For example, urines are usually kept for 48 hours. Bloods can go anywhere from 5 to 42 days depending on the tests clinicians ordered. But for the most part, like I mentioned before, it's about 7 days.

         This is where you would apply what you learned in school into practice. It's something I haven't appreciated as much until recently. Most of my current colleagues are not from the same training and academic background as me.

         A while ago, my colleagues approached me about missing cultures. Since I am currently the most senior MLS on my shift, I get questions often. This proved to be a great educational opportunity about different growth media.

Scenario 1: 14-day culture missing at day 10 with Group B Strep. on report.

         In most cases, a routine culture would last about 2-4 days. A 14-day culture implies the clinicians were suspecting fastidious organisms. In our case, this was a surgical site. This is one of those cultures you don't want to tell the surgeon the lab goofed up.

         Since the culture was on day 10, we no longer possess the original specimen. How do you salvage this? To start off, I looked into the patient history. The patient also had an 14-day anaerobic culture in progress. Our quest ended there. We have already identified the pathogen on aerobic side (the Group B). The anaerobic side would catch everything else that didn't grow on the aerobic side.

         What would happen if aerobic routine had no growth at day 10? The standard anaerobic culture includes an anaerobic blood agar (ABA). It's a sheep blood agar (SBA) that went through anaerobic conditions.

_{Textbook perfect thioglycolate broth}

         In that case, we would try to scrape off some inoculant from the ABA's first quadrant. Then, put them on a new set of routine cultures and even add a thioglycolate broth (thio for short). This way, we could still recover organisms in low numbers and let the new cultures grow. While this would delay patient results, it's better than losing them.

Scenario 2: Missing routine culture that was never set up

         This one was a bit annoying. Usually, I would go find the original specimen and reset them up. This time, however, the patient sample was not at the cached spot as expected. In other words, we had actually lost the specimen.

_{The BHI}

         Again, first step was to look up patient history. The patient also had a fungal and an acid fast culture in progress. A fungal culture includes a brain heart infusion (BHI) in its initial set up. A BHI is like a boosted version of the chocolate agar (CHOC), an enriched media. It looks very much like a SBA with a brighter shade of red. We could take whatever is growing on it and translate/transfer to our routine culture.

         And thus, the crew managed to salvage the patient tests before the point of no return.

         TL;DR: When cultures are missing, try resetting them up from samples. If not, try grafting from patient's other cultures, if possible. Only submit yourself to the physicians/pathologists when you exhaust all options.

Final Thoughts

         In school, one would learn about the different media and their properties. It's one thing to know about them. It's quite another to actually use that info in problem solving.

         From the scenarios, you could see that there's a level of redundancy in the workflow. That redundancy is what allowed the crew to continue patient testing. Losing cultures can be devastating for patient care depending on collection site. It's usually not difficult to recollect a urine sample or superficial swabs of wounds. The problem escalates when the samples involve deep wounds, tissues, etc.

         There's a lot of trust involved in patient care from beginning to end. While there are ways to catch mistakes along the process, we have to have competent actors. Otherwise, none of the assumptions I made during the troubleshooting process stand.

         Such is the way of working in a limited scope in a greater sphere.

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