Probiotics applied with dressings aided wound healing in horses, study finds

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Wounds covered in dressings saturated with a standardized suspension of probiotic bacteria healed faster than those dressed with a saline-soaked dressing, it has been reported.

The probiotic combination used on the wounds in the study in The Netherlands appeared safe, with no systemic effect found, the study team reported in the open-access journal PLOS ONE.

Probiotics are defined by the World Health Organisation as live microorganisms which, when given in adequate amounts, confer a health benefit on the host. They comprise non-pathogenic strains of bacteria.

Jacintha Wilmink, a veterinary surgeon who specializes in wound management and reconstruction in horses, led the study. She has been intensively treating wounds in horses for almost 25 years.

Wilmink and her fellow researchers, Søren Ladefoged, Angelique Jongbloets and Johannes Vernooij, set out to learn more about the effects of probiotic-soaked dressings in the treatment of lower leg wounds.

They hypothesized that topical probiotic treatment would stimulate equine wound healing, and would not cause a systemic inflammatory reaction.

For wounds to be included in the study, they had to be on the lower legs of horses and more than 10 square centimetres in size. They also had to be less than six months old. Wounds that involved complications such as penetration of the joint capsule were not included.

Most of the wounds originated from trauma, and a few from pressure. The horses were enrolled from six equine referral centres across Denmark and The Netherlands.

In all, 29 Warmblood horses were included in the study. The wounds of 15 horses were treated with probiotics, while those of the other 14 horses were treated with sterile saline.

The probiotic suspension used in the study contained strains of Lactobacillus acidophilus, Bifidobacterium animalis subsp lactis and Lactobacillus paracasei subsp paracasei. More details on the probiotic combination can be found here.

The wounds were allocated into two groups — those with an incomplete granulation bed and those with a complete granulation bed.

The progress of wound healing was evaluated for 24 days, after each wound was initially prepared for dressing the same way.

The dressings and bandages — identical apart from one group having them soaked in probiotic solution and the other in saline — were freshly applied at the start of treatment and then on days 1, 3, 6, 9, 12, 15, 18, 21 and 24.

Wounds on each occasion were gently cleaned with swabs moistened with sterile saline, during which exudate and debris were removed. Standardized digital photographs were taken for further evaluation.

Blood was taken three times from the neck for analysis, as were wound swabs for the identification of aerobic bacteria.

All horses were healthy at the start of the study and, apart from one horse that showed signs of upper respiratory tract infection on day 9, which resolved without treatment, the horses remained healthy throughout.

The study team found that the average relative wound area decreased faster in probiotic than saline-treated wounds.

The difference was most obvious in those with a complete granulation bed and increased rapidly from the first day of dressing until day 12 up to 30%, and stabilized around 25% thereafter until the end of the observation period.

The average wound area of complete granulation bed decreased to 28.4% with probiotic and to 51.9% with saline treatment at day 24.

Additionally, the rate to 50% healing in the wound with a complete granulation bed was 3.4 times faster with the probiotic combination compared to saline treatment, whereas in those with an incomplete granulation bed this was 1.9 times faster.

The topical use of the probiotic solution did not increase serum amyloid A (an acute-phase protein) and white blood cell counts, the blood work showed.

Faster wound healing

The clinical relevance of the effect of treatment with probiotics in wounds with a complete granulation bed is clear, they said. The probiotic-treated wounds reached 50% reduction in wound area in half the time of the saline-treated wounds.

“The topical use of probiotics can be considered as safe as it did not cause a systemic effect,” Wilmink and her colleagues reported.

Discussing their findings, the researchers said the fact that the effect of the probiotic dressing was most obvious in wounds with a complete granulation bed is likely to be the result of the more uniform healing curves within such wounds.

“The wound-healing tendency of probiotics in the current study is supported by the reduction of the amount of exudate and malodour, as well as a lower score for the number of bacteria and number of bacteria species in the probiotic-treated compared to the saline-treated wounds.

They continued: “The present study showed that the topical use of probiotics was well-tolerated by all horses and no systemic inflammatory reaction could be observed.

“The probiotic treated wounds reached 50% healing at day 12, whereas this was not completely reached for the saline-treated wounds at day 24. This means that within the 24 days evaluation, the probiotic treated wounds reach 50% reduction in wound area in half of the time of the saline-treated wounds.”

Wilmink is with the wound care practice Woumarec in Wageningen, The Netherlands; Ladefoged is with Højgård Horse Hospital in Morud, Denmark; Jongbloets is with the Horse Clinic West Brabant at Roosendaal, in The Netherlands; and Vernooij is with Faculty of Veterinary Medicine at the University of Utrecht in The Netherlands

Wilmink JM, Ladefoged S, Jongbloets A, Vernooij JCM (2020) The evaluation of the effect of probiotics on the healing of equine distal limb wounds. PLoS ONE 15(7): e0236761. https://doi.org/10.1371/journal.pone.0236761

The study, published under a Creative Commons License, can be read here

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