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Evaluation of novel Zinc-based antimicrobial formulations to control growth and biofilm formation of Xanthomonas citri and Liberibacter crescens.

Hajeewaka Mendis: Auburn University

<div>Zinkicide<sup>TM</sup> and TSOL are Zn-based antimicrobial formulations developed for treating citrus bacterial pathogens ‘<em>Candidatus</em> Liberibacter asiaticus’ and <em>Xanthomonas citri.</em> This study investigated the effects of Zinkicide<sup>TM</sup> and TSOL on growth and biofilm formation of ‘<em>Ca.</em> L. asiaticus’ surrogates <em>X. citri</em> and <em>Liberibacter crescens</em> in batch cultures and under flow conditions using microfluidic chambers (MC). <em>X. citri</em> and <em>L. crescens</em> were grown in SB and BM7 media, respectively, and treated with serial dilutions of Zinkicide<sup>TM</sup> and TSOL to test inhibition of growth and biofilm formation. <em>X. citri</em> and <em>L. crescens </em>were also introduced to MC and inhibitory action of Zinkicide<sup>TM</sup> and TSOL on biofilm formation was recorded using time-lapse video imaging microscopy. The minimum inhibitory concentration (MIC) of Zinkicide<sup>TM</sup> and TSOL for <em>X. citri</em> was 35 ppm and 40ppm, respectively. MIC of TSOL for <em>L. crescens</em> was 40 ppm. Both Zinkicide<sup>TM</sup> and TSOL have bactericidal effect on <em>X. citri </em>above 60 ppm and 150 ppm respectively. Time-lapse video imaging showed that untreated <em>X. citri</em> grown in MC formed biofilm whereas<em> X. citri</em> treated with 30 ppm Zinkicide<sup>TM</sup> did not form any biofilm. Furthermore, Zinkicide<sup>TM</sup> and TSOL inhibited further growth of already formed <em>X. citri</em> biofilm at 30 ppm and 60 ppm, respectively, in MC. Results confirmed that Zinkicide<sup>TM</sup> and TSOL are effective against <em>X. citri </em>and <em>L. crescens</em> in vitro and inhibit growth and biofilm formation under flow conditions.</div>