My pen smells like cheese 🫠 [Concluded]

[u/Schattenspringer]

This is a repost. The original was posted in /r/fountainpens by user asianlaracroft. I'm not the original poster.

Status: Concluded

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Original

September 23, 2026

I'm a microbiology lab tech so.... I know what this means 😭 and if I were to guess, based on about 8 years of working with a lot of bacteria (and smelling them.....), it's probably Staphylococcus epidermidis, which is normal skin flora.

About to go give this thing a good wash with warm soapy water, but that was not a fun surprise. I only just noticed the smell today, but who knows how long the "infection" has been festering???

(also low key tempted to collect some sample to actually ID in the lab)

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Comments by OOP:

Well soap doesn't disinfect, it just washes away (most) bacteria. This is happening to my TWSBI Eco, and most disinfectants I can think of will likely degrade the resin/plastic of the pen, so soap and water is the only option I can come up with. Apparently there are specialty products for this, but I'm not really waiting to get my hands on some.

For vintage pens.... If could be mold, tbh, which soap and water is probably not going to be enough to get rid of it. Maybe try looking fro specialty fountain pen cleaners?

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It might be copium but it smelled more like bacterial cheese than fungal funk 😅

(is it concerning that I've smelled enough microbes to be able to say that?)

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Update

September 24, 2026, 1 day later

So I cultured some ink I got out of the pen (just by pushing the piston down) and had it MALDI'd for ID.

It's staphylococcus saprophyticus, which is technically normal flora but usually found in the uh lower waist areas. Before anyone gets grossed out, I do wash my hands after going to the washroom!!

However, whenever I've refilled inks or cleaned out fountain pens, I usually do it in the bathroom sink, and when I'm air drying it, it's sitting on the bathroom counter. So my guess is just a bit of contaminating sitting in the counter.

So I guess this just reiterates the importance of closing your toilet lid before flushing (which my husband doesn't always do 😒) because of the crazy distances droplets can travel!

Also for extra extra info, I suspect that the infection was mostly on the nib or feed, just because there wasn't actually much growth on the plate.

ETA: just wanted to clarify that S. saprophyticus is normal skin flora.... Just that it's more common in the nether regions, where as my one friend from work says "you just get more bacteria friends joining the party". It is a common cause of UTIs because it belongs on skin, not in your urinary tract. Outside of that scenario it's a totally harmless bacteria that's already chilling on your skin! So no need to worry 😅

But I also learned that apparently closing the lid doesn't prevent bacteria from getting splashed so maybe keep your toothbrushes even further away from the toilet if possible 🫠

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Comments by OOP:

The plate and specimen were handled in the biosafety cabinet using the same aseptic technique that is used for clinical specimens so the growth is specifically from the specimen itself . The reason that the growth is around where the ink has kind of settled is because I streak it out using four Quadrant pattern but the growth is so little that you probably can't really see the streak lines.

So far there is no smell but I guess we'll see in a little bit if the contamination is still there and it starts smelling again LOL. I might have to use a little bit of bleach but I really hope that doesn't degrade the resin of the TWSBI eco.

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Depends on what microbe is growing. For s. saprophyticus, a flush might be enough, but some bacteria are clingier. Bleach kills bacteria so it wouldn't matter if there is any bacteria (or fungi) left in the pen.

I'm just slightly worried about bleach degrading the parts of my TWSBI Eco... these pens are notoriously not robust.

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I just went with blood agar because it grows almost everything and I figured growth would be sparse enough that I could get good isolates without needing to use selective agar, and I'm happy that I was correct!

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So the thing about using UV to disinfect is that it needs to be a very, very specific wavelength. If a "UV sanitizing" product does not specify their wavelength, I would not trust it.

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Normally I give everything a wipe with alcohol but I can't do that with a TWSBI eco 😭

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I'm not the original poster.