Antimicrobial Activity of Plasma Rich in Platelets (PRP) on the Ocular Microbiota of Healthy Horses from Minas Gerais: In Vitro Study

Abstract

In equine ophthalmology, ulcerative keratitis is among the most common conditions and, in general, arises as a consequence of some trauma suffered. Secondarily, subsequent contamination by pathogenic or resident bacteria of the horse's ocular microbiota may have undesirable consequences. Under physiological conditions, the normal microbiota coexists with the immune status of the host, serving as a barrier, ensuring the health of the ocular surface, and inhibiting the proliferation of pathogens. However, in the imbalance of immune barriers, the normal microbiota can become pathogenic and lead to infection, acting as an opportunistic agent. The present study aims to demonstrate the antimicrobial effect of platelet-rich plasma (PRP), its time of action, and its correlation with the concentration of its same components in vitro on Staphylococcus sciuri, a bacterium with high prevalence in the normal ocular microbiota of horses in the municipality of Minas Gerais. For the preparation of the PRP, eight adult Quarter Horse (QH) horses were used. The individual PRP was prepared by the double centrifugation protocol, and then, the PRPs were added to a pool, followed by testing their interaction in culture with Brain Heart Infusion (BHI) broth at different dilutions against five strains collected from different animals. After 3, 6, 12, and 18 hours, the colony formation units (CFU) count on a 5% horse blood agar plate was evaluated for each time point. Our study showed that Staphylococcus sciuri, the resident microorganism of the ocular conjunctival microbiota of horses, is more susceptible when compared to the standard strain "American Type Culture Collection" (ATCC-29213) Staphylococcus aureus, a pathogenic microorganism, which was used for the validation of our study. The antibacterial effect shown in this study was bacteriostatic for up to 6 hours. The most concentrated PRP dilutions, 1 : 1 and 1 : 2, were also most effective, suggesting that the antibacterial effect is volume dependent.

Figure 1

Design of the subgroups of each treatment.

Figure 2

-Means of CFUs/ml of the strains over time, considering all means of dilutions. ^∗S1–6: Staphylococcus sciuri; SS: Staphylococcus aureus. Different uppercase letters specify significant differences between strains for the same time, and different lowercase letters specify significant differences between times for the same strain, with a significance level of 5%.

Figure 3

Means of CFU/ml of the dilutions over time, considering the means of the strains. Different uppercase letters specify significant differences between dilutions at the same time. Different lowercase letters specify significant differences between times for the same dilution, with a significance level of 5%. ^∗PCG: positive control group.

Figure 4

Means of CFU/ml of the dilutions considering all the means of the strains and times grouped. ^∗PCG: positive control group. Different lowercase letters specify significant differences between groups.

Figure 5

Means of absorbance (A₆₂₀) of the strains over time considering all the means of the dilutions. ^∗S1–6: Staphylococcus sciuri; SS: Staphylococcus aureus. Different uppercase letters specify significant differences between strains at the same time. Different lowercase letters specify significant differences between times for the same strain, with a significance level of 5%.

Figure 6

Means of absorbance (A₆₂₀) of the dilutions over time considering the means of the strains. Different uppercase letters specify significant differences between dilutions at the same time. Different lowercase letters specify significant differences between times for the same dilution, with a significance level of 5%.

Figure 7

Means of the dilutions absorbance considering all strain means and times grouped. Different lowercase letters specify significant differences between groups.