I have acquired TB slides from my city's health center that are supposedly acid-fast bacteria (AFB) positive. However, when I took a look at it, I see basically no carbol fuchsin stains.
They were individually neatly folded in paper. When I opened them, the stains were slightly wet with immersion oil, facing down. So far, so good (page 6). I've been later informed that these samples were prepared Q1 2019. Based on my research, the staining solutions themselves last up to 12 months (page 33). I can't find any data on how long a stained sample would keep though.
Do they decolorize over time? I expected the AFB to be bright, or at least slightly pink, but I see no such thing. I do see bacilli, though all of them are nearly transparent/methylene blue in color.
Here are some sample images. The first 2 are how I expected AFB to look like, while the next 2 are what I captured (and I think should contain AFB). The last pic is a 10um/div calibration slide for reference.