299 Impact of antimicrobial bathing on canine dermal microbiota regrowth

Recent public health concerns have heightened concerns regarding the potential for contact transfer of bacteria from dogs to humans. Pathogenic bacteria including strains of Staphylococcus are of specific concern and have raised the question regarding the use of antimicrobial based bathing methods for potential mitigation. Common veterinary antimicrobial cleansers such as chlorhexidine gluconate have been suggested as possible decontamination cleansers. Chlorhexidine gluconate bathing has been well studied in humans. However, its use beyond surgical preparation is not well examined in canines. Therefore, the objective of this work was to identify the time frame associated with dermal microbial regrowth following an antimicrobial bath designed to mimic a decontamination procedure using chlorhexidine gluconate. Labrador Retrievers (n = 10) were assigned to treatment group (control = CON; chlorhexidine gluconate = CHX) and were bathed by a single trained technician using either water (CON) or chlorhexidine gluconate (CHX). Baths included the application of 280 mL of treatment (CON = water; CHX = 4% chlorhexidine diluted 1:4). Three dermal swabs were collected at the shoulder blades at baseline (prior to bathing) and across the following timepoints after the bathing procedure: 1 h, 12 h, 24 h, 36 h, and 48 h. Swab solutions were diluted to 108. All dilutions were plated on nutrient agar and incubated at 30° C for 44 to 50 h. Colony counts were measured to calculate final cells/mL concentration of samples. Mean concentration per timepoint for each canine was used for analysis using SAS on Demand with significance determined at P = 0.05. Mean concentration values over time compared with baseline were analyzed for effects of time, treatment group, and sex via PROC GLM between by within ANOVA. Time following bathing, treatment and sex significantly impacted bacterial regrowth (P < 0.0001). Bacterial growth did not differ significantly until 24 h following bathing at which point the CON group regrowth began. Dogs in the CHX group had reduced regrowth through the 48 h following bathing and failed to completely recover by 48 h post bathing. Males had increased regrowth compared with females in both CHX and CON groups. These results indicate a surprising time delay associated with antimicrobial bathing. The antimicrobial effect of chlorhexidine gluconate was not fully evident until 24 h and had differing impacts based on sex in the studied canines. Future studies should examine these findings in larger research cohorts with different breeds to identify impacts associated with coat type, sex, and more frequent sampling intervals.