Colloidal Iron Oxide Formulation for Equine Hoof Disinfection

SIMPLE SUMMARY: Horse hoof possesses a micro-flora that may promote the development of secondary infections following wounds or surgery. For this reason, in vitro and in vivo experiments were used to verify and compare the bactericidal power of two well-known disinfectants, Povidone-iodine (PI) and Chlorhexidine (CHx), and a new stable colloidal suspension of iron oxide, called Iron Animals (IA). In vitro, IA was able to completely suppress the bacterial growth on all of the tested microorganisms. In vivo, PI alone possessed the lowest efficacy for hoof disinfection; CHx resulted as the best treatment in 18% of cases. CHx + IA emerged as the best disinfection protocol for equine hoof achieving the lowest bacterial load in 55% of cases. The addition of IA, after PI or CHx, improved both disinfectants’ effectiveness, leading to the highest bactericidal activity in 82% of cases. IA would deserve a chance as a possible solution in pre-surgical disinfection of the equine hoof, reducing the risk of infection. ABSTRACT: The presence of bacteria of various origins on horse hoofs enables the onset of infections following trauma or even post-surgical wounds. Thus, the analysis of new antibacterial substances is of fundamental importance. In this study, the antibacterial efficacy of Iron Animals (IA), a stable colloidal suspension of iron oxide, organic acids, and detergents, was tested in vitro and in vivo. In vitro assays were performed to test the unspecific inhibitory effect of IA on both gram-positive and gram-negative bacteria monitoring the microorganism growth by spectrophotometry (optical density OD600) at 37 °C for 24 h. In vivo test consists on the quantification of the bacterial load in colony forming units per gram (CFU/g) of specimens collected from the frog region of the anterior hooves of 11 horses. Sampling followed the application of four disinfectant protocols consisting of two consecutive 3 min scrubs with 50 mL of 10% Povidone-iodine (PI) or 4% Chlorhexidine (CHx), with or without an additional application for 15 min of 10 mL of Iron Animals (PI+IA and CHx+IA). In vitro, IA completely suppressed the bacterial growth of all the tested microorganisms, resulting in effectiveness also against CHx-resistant bacteria, such as Staphylococcus aureus. In vivo, PI emerged as an ineffective protocol; CHx was effective in 18% of cases, but with the addition of IA (CHx + IA) its use emerged as the best disinfectant protocol for horse hoof, achieving the lowest bacterial load in 55% of cases. The addition of IA, after PI or CHx, improves the effectiveness of both disinfectants leading to the highest bactericidal activity in 82% of cases.