Curcumin shows promise as an adjunct in changing β-lactam susceptibility status of canine multidrug-resistant...

Methicillin-resistant Staphylococcus pseudintermedius (MRSP) has become increasingly widespread in veterinary medicine, with a reported prevalence of up to 40.5% in dogs with pyoderma. Previous studies have shown that curcumin derived from turmeric (Curcuma longa L.) exhibits a synergistic effect when combined with β-lactam antibiotics, fluoroquinolones, tetracyclines, or vancomycin against strains of Staphylococcus aureus, including both methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) isolates. Thus, the purpose of this study was to determine whether curcumin (500 µg/mL), in combination with oxacillin, amoxicillin-clavulanate, clindamycin, or doxycycline, could improve the susceptibility status of each antibiotic against multidrug-resistant Staphylococcus pseudintermedius (MDR-SP). Clinical isolates collected from dogs with MDR-SP pyoderma were tested against each antibiotic at their respective Clinical and Laboratory Standards Institute resistant, intermediate, and susceptible concentrations, in the presence or absence of curcumin. An ATCC methicillin-susceptible S. pseudintermedius reference strain (ATCC 49444) was included as an internal quality control. Exact McNemar test was used to assess paired isolate-level comparisons and a value of p < 0.05 was considered significant. A significant shift toward susceptibility was observed when curcumin was combined with oxacillin at the resistant (p = 0.001) and the susceptible (p < 0.0001) concentrations and with amoxicillin-clavulanate at the resistant (p = 0.002) and intermediate (p = 0.0078) concentrations. Amoxicillin-clavulanate at the susceptible concentration when combined with curcumin was not significant (p = 0.0625). Curcumin did not significantly alter the susceptibility status of clindamycin or doxycycline at any of the tested concentrations. Bactericidal concentrations were not observed at the tested concentrations. These results suggest that curcumin may potentiate the efficacy of select β-lactam antibiotics against MDR-SP, supporting curcumin as a potential β-lactam adjuvant against MDR-SP in vitro and warranting further evaluation.