This is another great example of how volunteers spot things that we, the professional scientists, miss.
All of these occurred in images with 7 wells and there were two main artefacts: (1) a scratch in well 3 and (2) a fuzzy arc in different positions in well 7. A good, clear example of a fuzzy patch in well 7 is shown below.
Now we have seen scratches before so I wasn’t so concerned about those – we would talk to the lab involved and there would be a reason – but what is going on in well 7. It turns out all these images were taken by one lab and they all have a single antibiotic, clofazimine (CFZ). This is an old drug that at present isn’t used to treat tuberculosis, but may be useful given the rise of multi-drug resistance tuberculosis. Amazingly when I emailed the project coordinators, they said
This is interesting and is most likely CFZ crystallisation. It helps explain these images I got when we were all worried about CFZ crystallising at high concentrations.
So it isn’t contamination or condensation, but instead is the drug forming crystals, which explains why you only see it in well 7 because that is the well with the largest amount of CFZ. It also explains why it looks fuzzy and is never in the same place. Even better, it turns out clofazimine crystals are orange! (Unfortunately the images we show you are black and white). This is a photograph sent from one of our labs in Asia.
So please keep tagging me in the Talk Boards if you think you’ve seen a new artefact. Not only can we share it with the other volunteers, but we can add it to the Standard Operating Procedure manual that each lab has and also test to see if our automated plate-reading software is confused by it or not.