Aquarium Bacteria Turns a “Spider Bite” Into a Tough Skin Puzzle

A 51‑year‑old woman who had undergone weight‑loss surgery developed a stubborn wound on her wrist that refused to heal.
Initially, she believed it was a spider bite after visiting a farm and sought emergency care multiple times. She received standard antibiotics, yet the skin issue worsened, prompting doctors to consider common skin infections.

After weeks of no improvement, a laboratory test on a wound sample identified Mycobacterium marinum, a slow‑growing bacterium typically associated with water exposure—especially prolonged contact with fish tanks or other aquatic environments.
The patient had no recollection of owning an aquarium until clinicians probed further, uncovering the true source.

Treatment proved challenging because her altered stomach from prior surgery impaired oral antibiotic absorption. The care team switched to long‑term intravenous therapy administered at a clinic, ultimately clearing the ulcer.

Takeaways

• Avoid premature conclusions. A seemingly obvious cause (spider bite) can mask a more complex etiology.
• Probe all water exposures. Ask about aquariums, fountains, or any aquatic contact, not just swimming pools.
• Consider atypical bacteria. When wounds fail to heal with standard antibiotics, test for uncommon pathogens.