Seaweed Poultices and Vibrio Infection

By Carol A. Kemper, MD, FACP

Clinical Associate Profes sor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center

Dr. Kemper does research for Abbott Laboratories and Merck. This article originally appeared in the December 2011 issue of Infectious Disease Alert. At that time it was peer reviewed by Timothy Jenkins, MD, Assistant Professor of Medicine, University of Colorado, Denver Health Medical Center. Dr. Jenkins reports no financial relationship to this field of study.

Source: ProMED post, Oct. 20, 2011. Available at:

This report details the occurrence of an infected, cellulitic lower extremity wound infection in a 70-year-old British woman secondary to an unusual Vibrio species, V. alginolyticus. The woman was otherwise in good health, and she liked to take a daily swim in the sea off Guernsey (near the Channel Isles). She first injured her leg on a pot in the garden, and for 2 weeks had applied a home-made seaweed poultice to the wound, which she had created by extracting the alginate gel from the receptacles (knobby bladder-like organs at the end of fronds) of a local seaweed called spiral wrack. The wound had initially seemed to heal and crust over, then broke open, becoming weepy, swollen, and erythematous. The organism was recovered from both the wound and from seaweed samples collected from the beach near her home. She responded well to doxycycline.

Popular opinion holds that sea bathing and saltwater promote wound healing, and seaweed preparations have a long history as a home-based remedy. Commercial products increasingly incorporate alginate gels, which are absorbent and appear to promote wound healing. Unfortunately, home-based remedies do not use sterilized material, and seaweed can be contaminated with bacteria.

Changes in ocean temperature raise concerns that microbial flora in seawater and seaweed may be changing. Reports from Northern Europe suggest there has been an increase in serious infections from Vibrio spp. V. alginolyticus is a salt-tolerant (halophilic), Gram-negative bacilli found in more temperate seawater, such as coastal areas and estuaries. While unusual, infections occur more commonly in the summer months, when the water is warmer. Infections from this organism generally result in superficial wound infection, and external and middle ear infection, but can occasionally result in severe cellulitis, necrotizing fasciitis, bacteremia, and sepsis. Home-based seaweed poultices should be discouraged.