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Chronic wounds usually don't need antibiotics.

VANCOUVER, B.C. -- If physicians had a better understanding of the bacteriology of chronic wounds, they would stop overprescribing antibiotics for this indication--a strategy that rarely works and contributes to antibiotic resistance.

That's the assessment of Dr. Brian Kunimoto, director of the Wound Healing Clinic at the Vancouver Hospital and Health Sciences Centre and a member of the dermatology faculty at the University of British Columbia in Vancouver.

"Is there a problem with bacteria that grow in wounds, convincing some of us to do silly things like order useless tests, and worse yet, actually act on such useless information ... [by] prescribing drugs that have no chance of working? I think it's a big problem, and it has nasty consequences," said Dr. Kunimoto at the annual meeting of the Pacific Dermatologic Association.

Wounds come in many forms, with bacteria acting as attackers that have more or less of an impact depending on the vulnerability of the host as well as their own numbers and virulence, he said. (See box, lower right.)

When bacteria are planktonic, they live an independent, nomadic life, disorganized and generally in a fluid state. In this form, they pose little threat to a human host. But when they begin to unite in an organized, adherent, cooperative "city-state," they form a biofilm that poses a considerable challenge to physicians, Dr. Kunimoto said. About 65% of all bacterial skin infections are related to biofilms, characterized by their creamy, adherent properties.

"You brush off a biofilm every night when you brush your teeth. The classic biofilm is plaque on your teeth," he said.

Biofilms are made up of an exopolysaccharide matrix that allows for intracellular communication, production of a food supply, an escape route for waste, and most troubling, the sharing of genetic information.

A biofilm is polymicrobial, allowing for a harmonious existence of many forms of bacteria. "I think bacteria do a better job at multiculturalism than our country, Canada," he mused.

Culturing a biofilm is useless, Dr. Kunimoto maintained. "It's no different from culturing your nose. You will find--wow!--bacteria! It gives us no really useful information."

A culture may identify some bacteria present in the biofilm, but it will not characterize the rich and diverse population flourishing in a wound.

Moreover, neither topical nor systemic antibiotics penetrate a biofilm effectively, so they will be impotent, or worse, will provide highly useful resistance information to bacteria essentially sharing a bulletin board in a bustling city.

The best clinical practice for attacking biofilms is relentless debridement, according to Dr. Kunimoto. "As I say to the residents in the clinic, 'Don't slough sloughing the slough.'

"Don't throw an antibiotic at this. Get out your tools and dig away. Don't give up," he said.

Several antimicrobial agents can be used as adjuncts, including silver, starch iodine, and even manuka honey, Dr. Kunimoto said.

But the most critical treatment is repeated debridement, performed, if necessary, after a lengthy (2- to 3-hour) application of a topical anesthetic such as EMLA, he said.

Antibiotics are of use only in true clinical infections.


Los Angeles Bureau

RELATED ARTICLE: Nitric Oxide Gas Wards Off Bacteria

VANCOUVER, B.C. -- In the frustrating war against chronic wounds, Dr. Brian Kunimoto and his associates at the University of British Columbia, think they may have found a secret weapon that comes in a tank.

It's nitric oxide gas--a naturally produced, lipophilic molecule that, unlike antibiotics, easily penetrates biofilms, well-organized populations of bacteria that can form in chronic, difficult-to-heal wounds.

"I call it a smoking gun," said Dr. Kunimoto, director of the Wound Healing Clinic at Vancouver Hospital and Health Sciences Centre. Nitric oxide combines with reactive oxygen to create "an entire soup of bacteriocidal intermediates" in a wound, and poisons the iron enzyme aconitase. Facing this onslaught, "unless a bacterium can quickly develop into an anaerobic organism, it will die." Nitric oxide also deaminates DNA and enhances the damaging effects of hydrogen peroxide, he said at the annual meeting of the Pacific Dermatologic Association.

Studies at the University of British Columbia found that counts of bacteria, including Staphylococcus aureus, pseudomonas, and methicillin-resistant S. aureus, plummeted to zero within hours of exposure to gaseous nitric oxide.

Home therapy involving nighttime exposure to the gas quickly healed a 2-year-old, nonhealing ankle ulcer in a 55-year-old man with severe venous disease, said Dr. Kunimoto, who recently published the case (J. Cutan. Med. Surg. 2004;8:233-9). "This is remarkable.... We worked on him for 2 years and got nowhere," he said. "We've shifted the balance in favor of the host."

The Canadian government has recently approved funding for a large study of nitric oxide gas to see if the results can be duplicated in other nonhealing wounds.

How to Identify Wound Types

Wound Type: Contamination

Example: Fall from a bike, abraded skin.

Bacteria: "Just passing through."

Signs and symptoms: None.

Healing: Not compromised.

Testing: None necessary.

Treatment: Cleansing with normal saline.

Wound Type: Simple Colonization

Example: Wound of a few days' duration.

Bacteria: Living in the wound, but plank-tonic and disorganized.

Signs and symptoms: None of note.

Healing: Not compromised.

Testing: None required.

Treatment: Cleansing with normal saline.

Wound Type: Complicated Colonization (Biofilm)

Example: Chronic wound.

Bacteria: Significant in numbers and virulence. Well organized, often as a "biofilm."

Signs and symptoms: New onset of wound pain and wound-bed deterioration (granulation tissue loss, friability of granulation tissue).

Healing: Compromised.

Testing: None required.

Treatment: Aggressive debridement, possibly with adjunctive antimicrobial measures (such as manuka honey or starch iodine).

Wound Type: Clinical Infection (Rare)

Example: Markedly worsening chronic wound.

Bacteria: Very significant in numbers and virulence.

Signs and symptoms: Significant in numbers and virulence. Well organized, often as "biofilm." There is evidence of a host inflammatory response (cellulitis) and possible systemic toxicity (fever and malaise).

Healing: Compromised.

Testing: Wound biopsy of base preferable to culture.

Treatment: Systemic antibiotics.

Source: Dr. Kunimoto
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Title Annotation:Dermatology; annual meeting of the Pacific Dermatologic Association
Author:Bates, Betsy
Publication:Internal Medicine News
Geographic Code:1CBRI
Date:Feb 1, 2006
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