In vitro interactions of thymol in combination with antimicrobials against carbapenem-resistant Acinetobacter baumannii and multidrug-resistant Klebsiella pneumoniae clinical isolates.

We evaluated in vitro activity of thymol in combination with β-lactams, gentamicin, or colistin against Carbapenem-Resistant Acinetobacter baumannii (CRAb) and KPC-producing Klebsiella pneumoniae (KPC-Kp) clinical isolates displaying different susceptibility profiles. Thymol, when combined with β-lactams, did not exert synergistic interactions, whereas in association with colistin it showed additive or synergistic activity against 85.7% (6/7) and 14.3% (1/7) of MDR-GNB clinical isolates, respectively. These results showed that thymol in association with colistin may be considered a potential strategy that warrants further investigation as a potential antimicrobial-adjuvant strategy for patients colonized by MDR-GNB clinical isolates, also hypothesizing the ability to reduce the spread of emerging resistance traits.