Fungal Communities Associated with Delayed Wound Healing

A new study reveals that fungal communities found in chronic wounds can form mixed bacterial-fungal biofilms that are associated with poor outcomes and longer healing times.

Researchers at the University of Pennsylvania (Penn; Philadelphia, USA) and the University of Iowa (Iowa City, USA) profiled 100 patients with non-healing diabetic foot ulcers (DFUs) during the course of 26 weeks, until the wound healed, or until the foot required amputation. All of the patients were given the same medical care, with the researchers sampling deep wound fluid every two weeks. The samples were sent for genetic sequencing and identification of the fungi residing in the wounds.


High-throughput sequencing found that about 80% of the DFUs contained fungi from 284 different species. The most abundant fungus, Cladosporium herbarum, was found in 41% of the samples, and the human pathogen Candida albicans was the next most abundant, in a little over one-fifth of the samples. No single species was associated with poor outcomes, but rather mixed communities were associated with slow healing, or complications such as osteomyelitis and amputation. Higher levels of ascomycetes at the initial swabbing were associated with wounds that took longer than 8 weeks to heal.

Two of the patients' wounds were examined more closely to determine if their stable communities of microbes could grow biofilms, which are thought to keep many chronic wounds festering. One wound, which eventually healed, contained C. albicans yeast and Citrobacter freundii bacteria. Another wound that resulted in amputation contained the fungus Trichosporon asahii and the bacteria Staphylococcus simulans. When the bacterial-fungal pairs were co-cultured in the laboratory, both formed a mixed biofilm. The study was published on September 6, 2016, in mBio.

“Chronic wounds are a silent epidemic,” said senior author Elizabeth Grice, PhD, an assistant professor of dermatology and microbiology at the University of Pennsylvania. “They usually occur in conjunction with another disorder such as diabetes or obesity, but once a chronic wound occurs, it requires a lot of healthcare and has a devastating effect on a patient's quality of life.”

Diabetes patients often suffer from nerve and circulation problems in the feet, which reduce their perception of pain. The nerve pathways that ensure that weight is automatically transferred from one foot to the other during prolonged standing are disrupted, and as a result, diabetics do not notice that their toes, heels, or the balls of their feet are too heavily loaded. The foot receives no relief, and pressure sores, ulcers, and infections may go unnoticed. Serious DFU cases may lead to amputation.

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