In the scenario where your laboratory finds contamination, what troubleshooting step would you take?

How to Answer
Answer Example
Community Answers

Don't ask what type of contamination! It's irrelevant since the interviewer wants to know if you have experience dealing with contamination (most laboratory professionals do) and how you were able to control it. Reflect on a time when you might've dealt with contamination in the lab. If you are early in your career, then think about experience with this as a student and what you might've learned from instructors and other professionals.

"In several PCR runs, I noticed the internal control was unusually positive in all samples. What was especially alarming is that it was positive in the negative control samples as well. This occurred on several runs on all of the machines leading me to believe it was a contamination issue rather than a specific failure related to reagents, equipment, or human error. I implemented the addition of Uracil-DNA Glycosylase (UNG) to the PCR assay to prevent carryover contamination between PCRs. This technique proved to be successful in future runs."

Anonymous Answer

"If I encounter microbial growth and contamination while working on a sample in the lab, my first step is to determine the cause. If it was due to my own mistake, I would restart the entire process. I then assess if the sample is salvageable and, if so, use specialized techniques such as autoclaving, filtration, or centrifugation to clean and sterilize it. However, if the issue was caused by an external factor, such as another researcher's sample, I would contact them to see if it's possible to redo the work. In all cases, I document everything that happens to learn from my mistakes and improve my process."

Marcie's Feedback

Exactly how would you determine the cause? What steps would you take to figure this out? Also, has this happened to you before? If so, don't hesitate to provide a real-life example to make your answer even more memorable. Great job!