Bilophila wadsworthia

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Bilophila wadsworthia is a Gram-negative, obligate anaerobe that likes bile and does not use sugars. Most strains can break down compounds with urease, but not all.

Key features
- It produces hydrogen sulfide (H2S) from taurine, a process linked to its role in the gut and sometimes to disease.
- It has a rapid, vigorous catalase reaction with hydrogen peroxide.
- It grows slowly in standard anaerobic cultures, which can lead to misidentification.

What makes it unique
- Uses taurine from alkylsulfonates to make H2S via the IslA enzyme.
- Its H2S production is a noticeable trait and can affect the gut environment.

Appearance and growth in the lab
- On BBE agar, it forms colonies with a black center due to ferrous sulfide; you may see two types: small convex colonies with a black center or translucent, umbonate colonies with a dark center. Requires at least 3 days to grow.
- On Brucella agar, colonies are gray, translucent, and 0.6–0.8 mm after about 4 days.
- Favorite growth conditions: about 20% bile and 1% pyruvate.

Where it’s found and clinical relevance
- Mostly lives in the lower gastrointestinal tract.
- Associated with appendicitis (including gangrenous forms) and liver abscesses; it’s one of the more common anaerobes found in appendicitis.
- Also found in healthy feces and, less often, in dogs with periodontal disease; rare in saliva or vaginal samples.
- H2S production can contribute to disease processes, and antibiotic use can sometimes allow opportunistic growth.

Identification tips
- A transparent colony with a black center on BBE agar is a strong clue.
- Gas chromatography often shows many acetic acid peaks and little succinic acid.
- Catalase test with 15% hydrogen peroxide can yield an explosive, rapid reaction.
- It is non-motile, non-spore forming, with irregular cell walls and no flagella.

Antibiotic sensitivity
- Generally susceptible to beta-lactam antibiotics such as imipenem, cefoxitin, and ticarcillin.

History
- First identified in 1988 by Ellen Jo Baron, and named Bilophila because of its bile-loving nature.