Antimicrobial activity of organic acids against canine skin bacteria

Canine skin is often a source of bacterial strains that are characterized by the presence of important virulence factors and a high antimicrobial resistance. These bacteria are involved in the pathogenesis of infectious skin diseases, which are very frequent in dogs. Moreover, canine skin isolates are easily spread to other animals and humans. The aim of this study was to evaluate the inhibitory and bactericidal activity of eight organic acids (L-lactic, acetic, propionic, butyric, citric, succinic, glycolic, L-ascorbic acid) against 14 canine skin isolates (11 Gram-positive and three Gram-negative species). The advantages of the tested organic acids are their gentleness to the skin and their affordability. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by the broth microdilution method. All tested acids showed a bactericidal effect against the selected bacteria, with the exception of their bacteriostatic effect against the Bacillus cereus strain. The lowest MIC showed acetic acid (MIC between 0.5 and 2.0 mg/mL) and propionic acid (MIC 0.8 – 3.3 mg/mL), whereas L-ascorbic acid (MIC 4.0 – 16.0 mg/mL) seems to be weaker among the tested acids. Two Staphylococcus aureus strains and a strain of Escherichia coli were observed to be more resistant compared to coagulase-negative staphylococci.