By Gary M. White, MD

Pseudomonas infection under the nail

The bacteria Pseudomonas may infect the undersurface of the nail if the nail becomes separated from the nail bed (onycholysis). It is common in persons whose hands are constantly exposed to water, soaps, and detergents or are subject to mechanical trauma, especially in the elderly.


The nail takes on a characteristic green color (chloronychia) in the area of the onycholysis. The infection and discoloration are on the undersurface of the nail.


Gentamicin solution (e.g., Otic) applied under the nail BID is usually rapidly effective. In order to clear both the onycholysis and the Pseudomonas, it is best to cut the nail way back, removing most of the green portion of the nail and then applying the gentamicin solution QAM and clotrimazole solution at night to clear any Candida (or gentamicin QPM and clotrimazole QAM).

Topical antibiotics (polymyxin B or bacitracin) applied 2–4 times daily for 1-4 months have been demonstrated to be effective in immunocompetent patients. Topical therapy with nadifloxacin applied once daily for several weeks was curative for two HIV- positive patients. Alternatively, oral ciprofloxacin may be given for 2–3 weeks [Clin Interv Aging. 2015; 10: 265].

See treatment onycholysis.

Additional Pictures

Pseudomonas infection under the nail

Greenish discoloration of the web spaces indicates Pseudomonas colonization/infection.
Pseudomonas infection of the web space

Pseudomonas green discoloration of the nail


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