Anette Thompson explains the use of probiotics in diabetic foot ulcer treatment.

Treating diabetic foot ulcers

Diabetic foot wound care practitioners understand that the three pillars of foot ulcer healing consist of: tight blood glucose control; offloading of pressure on the wound; and optimum care of the wound itself (ensuring good blood supply to assist the wound healing process).

Good blood supply delivers nutrition to the wound, although the word nutrition in diabetes has other dietetic connotations. In the past decade, emerging research into the specifics of the wound bed environment has brought further understanding of such entities: wound biofilm; proteases (protein destroying enzymes); colonisation by microorganisms and antibiotic resistance.

Wound dressing companies have developed specialised dressings to address each wound scenario, bringing in different approaches to break down biofilm, reduce the harmful bacterial load and stimulate tissue growth.

Biofilms

Biofilms are complex microbial communities containing bacteria and fungi. The microorganisms produce and secrete a protective matrix that attaches the biofilm firmly to a living surface, such as in a wound, or a non-living surface, such as an instrument⁷.

Biofilms are dynamic heterogeneous communities that are continuously changing³. They may consist of a single bacterial or fungal species, or may be polymicrobial, i.e. contain multiple diverse species⁹.

In a wound, you can imagine the biofilm as a densely-packed colony of bacteria embedded in a thick, slimy barrier of sugars (polysaccharides) and proteins. The biofilm barrier protects the harmful microorganisms beneath from external threats.

Probiotics

Most people will have heard of probiotics (a substance which stimulates the growth of microorganisms, especially those with beneficial properties) as a supportive treatment to gastrointestinal disorders. The human gut is naturally populated with millions of beneficial bacteria which in healthy individuals exist in balanced colonies, collectively called our gut microbiome.

Antibiotics destroy both beneficial and harmful bacteria, hence one should administer probiotics with a course of antibiotics (but not to be taken at the same time of the day). An imbalanced microbiome or dysbiosis is related to both gastrointestinal problems, such as diarrhoea and inflammatory bowel disease but also, outside the gut, such as obesity, allergy and skin disorders ¹².

Most early studies in the literature regarding skin outcomes were those in which probiotics were taken orally. Newer studies are investigating topical application but there are limitations due to a lack of regulatory consensus in different parts of the world.

2010 research

In 2010, medical researchers, in Tucuman, Argentina, tested bacteriotherapy with lactobacillus plantarum (probiotic) on infected chronic leg ulcers⁶.

They produced a culture of the probiotic and applied it to the wounds of 14 diabetic patients and 20 non-diabetic patients. Wound debridement (clearing of dead tissue), granulation tissue formation (healthy new tissue containing new blood supply) and total healing after 30 days were found in 43% of diabetics and in 50% non-diabetics.

When the researchers looked at cells from the wounds after 10 days, they found that there was a decrease in the percentage of diseased and necrotic (dead) cells and an enhancement of interleukin-8 production.

Interleukin-8 (IL-8), now renamed CXCL8, is an important mediator of the immune reaction in one’s immune system response. It has two main functions:

• It is the primary cytokine (messenger protein) involved in the recruitment of neutrophils (white blood cells that fight infection) to the site of damage or infection – in a process called chemotaxis⁴. This causes target cells, primarily neutrophils but also other granulocytes, to migrate toward the site of infection. It induces phagocytosis (engulfing of the bacteria to destroy them) once they have arrived.
• It is also known to be a potent promoter of angiogenesis (formation of new blood vessels).

Probiotic strains

There are hundreds of different probiotic strains. Even within the genus lactobacillus, there are more than 150 different species, such as L plantarum, L acidophilus, L reuteri and L rhamnosus to name a few.

Many of these are found in fermented food items, such as yoghurt, kefir, kimchi, sauerkraut and salt-pickled vegetables. Within each species, there are further hundreds of strains which are numbered, such as Lp299v.

Probiotics can strengthen the immune system, reduce inflammation and promote wound healing through an array of mechanisms, such as the production of inhibitory substances like acids or bacteriocins; excretion of natural antibiotics; blockage of pathogen adhesion; nutrient competition and antioxidant activity⁸. Painstaking research is required to pinpoint the exact effect of each strain on the body before any claims can be made.

Latest research

In 2016, continuing research, at the national university in Tucuman, Argentina,¹ designed two pharmaceutical dosage forms by using lactobacillus plantarum culture supernatants (clear liquid left above the solids after spinning in a centrifuge to concentrate the cells). These formulations have been cleared for use in clinical trials on chronic wounds that lack good blood supply (ischemic wounds).

Animal studies

Animal studies have been used to investigate the efficacy of probiotics, such as L brevis, L fermentum, L plantarum and L reuteri, as treatment for skin wounds. A meta-analysis of animal studies performed, in early 2017,¹⁰ found that probiotics administration is an effective pharmacological treatment of cutaneous animal wounds but further research is required.

Diabetic foot ulcer study

Late last year, a study at Babol University of Medical Sciences in Iran, tested the benefits of probiotic administration in patients with diabetic foot ulcers⁵. Patients with a diabetic foot ulcer who received probiotic supplementation for 12 weeks experienced faster wound healing coupled with an improved glycaemic and lipid profile compared with patients who had been assigned a placebo, according to findings from a randomised double-blind, placebo-controlled trial.

The probiotic capsules contained L acidophilus, L casei, L fermentum and Bifidobacterium bifidum. All participants also underwent standard treatment for wound care.

Probiotic supplementation also influenced lipid profile and inflammatory markers when compared with placebo. The researchers noted that information was not collected on faecal bacteria loads before and after probiotic administration, or on the characterisation of the microbiome at baseline, during and after therapy and bacterial cultures were not taken (a shortcoming of the study).

Lactic acid bacteria

Most recently, Dr David Armstrong reports, from the USA, that researchers are showing faster wound healing following the administration of lactic acid bacteria into wounds.

He refers to a study by Vågesjö et al., published online in the Proceedings of the National Academy of Sciences of the United States of America, that used a mice model to show wound healing.

Researchers transformed lactobacilli with a plasmid encoding chemokine 12 (CXCL12), noting that this enhanced wound closure via proliferation of dermal cells and macrophages. It also resulted in more transforming growth factor-beta (TGF-β) expression in macrophages. The study notes that bacteria-produced lactic acid reduced the local pH, which inhibited the peptidase CD26 and facilitated a higher availability of bioactive CXCL12.

The authors also note that lactobacilli delivering CXCL12 improved wound closure in mice with hyperglycaemia or peripheral ischemia, conditions associated with chronic wounds. The study adds that the treatment showed macrophage proliferation on human skin in an in vitro model of wound epithelialisation.

Final note

This is exciting news—although admittedly in early days—that we can use a probiotic (lactobacillus species) that is already a part of our beneficial bacterial microbiome² and enable it to produce, in this case, CXCL12, which may have positive wound healing attributes.

REFERENCES

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2. Dixit N, Simon SI (2012). Chemokines, selectins and intracellular calcium flux: temporal and spatial cues for leukocyte arrest. Frontiers in Immunology. 3: 188. doi:10.3389/fimmu.2012.00188. PMC 3392659 Freely accessible. PMID 22787461.
3. Hall-Stoodley L, Stoodley P. Evolving concepts in biofilm infections. Cell Microbiol 2009; 11(7): 1034-43.2.
4. Modi WS, Dean M, Seuanez HN, Mukaida N, Matsushima K, O’Brien SJ (1990). “Monocyte-derived neutrophil chemotactic factor (MDNCF/IL-8) resides in a gene cluster along with several other members of the platelet factor 4 gene superfamily”. Hum. Genet. 84 (2): 185–7. doi:10.1007/BF00208938. PMID 1967588.
5. Mohseni S, Bayani M, Bahmani F, et al. The beneficial effects of probiotic administration on wound healing and metabolic status in patients with diabetic foot ulcer: A randomized, double-blind, placebo-controlled trial. Diabetes Metab Res Rev. 2017;e2970.
6. Peral MC, Rachid MM, Gobbato NM, Human Martinez MA and Valdez JC. Interleukin-8 production by polymorphonuclear leukocytes from patients with chronic infected leg ulcers treated with Lactobacillus plantarum. Clin Microbiol Infect 2010 Mar; 16(3):281-6
7. Stoodley P, Sauer K, Davies DG, Costerton JW. Biofilms as complex differentiated communities. Annu Rev Microbiol 2002; 56:187-209.
8. Tavaria F Topical use of probiotics: the natural balance. Porto Biomed J. (Portugal) 2017:2(3):69-70.
9. Trengove NJ, Stacey MC, McGechie DF, Mata S. Qualitative bacteriology and leg ulcer healing. J Wound Care 1996; 5(6): 277-80.
10. Tsiouris, Christos G., Martha Kelesi, Georgios Vasilopoulos, Ioannis Kalemikerakis, and Effie G. Papageorgiou. 2017. “The efficacy of probiotics as pharmacological treatment of cutaneous wounds: Meta-analysis of animal studies”. European Journal of Pharmaceutical Sciences. 104 (8): 230-239.
11. Vågesjö E, Öhnstedt E, Mortier A, et al. Accelerated wound healing in mice by on-site production and delivery of CXCL12 by transformed lactic acid bacteria. Proc Natl Acad Sci USA. 2018;115(8):1895-1900.
12. Vandenplas,Y, Huys G, Daube G. Probiotics: an update. J Pediatr (Rio J Brazil) 2015;91:6-21).
    

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