The capacity of different naphthoquinones to inhibit and eradicate Yersinia enterocolitica biofilm was investigated and possible mechanisms of action were evaluated. Inhibition of biofilm formation and cell viability, quorum sensing (QS) inhibition and oxidative stress generation of 23 naphthoquinones were assayed against Yersinia enterocolitica. The best anti-biofilm agents at 100 µmol l-1 were compounds 3, 11 and 13, which showed biofilm inhibition higher than 75%. Compound 3 was the most effective against biofilm forming capacity of Y. enterocolitica WAP 314 with a minimum biofilm inhibitory concentration (MBIC) of 25 µmol l-1; while against Y. enterocolitica CLC001, the lowest MBIC was 6.1 µmol l-1 for compound 11. Acyl-homoserine lactones production was decreased with compound 13. We showed that the oxidative stress influence biofilm growth, by means of ROS and RNI increment. All treatments increased ROS and RNI values in the biofilm of both strains; while in planktonic cells, the increase was lesser. Additionally, Y. enterocolitica WAP 314 biofilm treated with compounds 11 and 13 showed above 80% of SOD consumption. In Y. enterocolitica CLC001 biofilm all compounds induced above 90% of SOD consumption. The SOD activity was higher in biofilm than in planktonic cells. In conclusion, this is the first study to demonstrate that naphthoquinones are able to inhibit biofilm formation of Y. enterocolitica without critical disturbing its planktonic growth. Naphthoquinones as anti-biofilm agents might potentially be useful in the treatment of biofilm-associated infections in the future.
Keywords: Biofilm; Naphthoquinones; Oxidative stress; Quorum sensing; Yersinia enterocolitica.