A modified formulation of <i>Zoono GermFree24</i> antiseptic liquid has enhanced efficacy against biofilms of <i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa</i>

<i>Zoono GermFree24</i> is a quaternary ammonium compound-based hand sanitiser. Its efficacy against planktonic bacteria is well established, but efficacy against biofilms has not been tested. We investigated the antibiofilm efficacy of <i>Zoono GermFree24</i> hand sanitiser and a modified formulation against biofilms of <i>Staphylococcus aureus</i> ATCC 6538 and <i>Pseudomonas aeruginosa</i> ATCC 27853 grown <i>in vitro</i> using the Centers for Disease Control (CDC) biofilm reactor and 96-pin lids. Biofilms were immersed in <i>Zoono GermFree24</i> or <i>Zoono</i> B22-1402A (modified formulation) for 5 min, 1 h, 6 h or overnight (22 ± 2 h). The antiseptic was neutralised and the bacteria remaining after treatment were cultured and quantified. <i>Zoono GermFree24</i> and <i>Zoono</i> B22-1402A caused time-dependent reductions in viable biofilms of both species with both methods of culture and testing, with more rapid biofilm eradication observed for <i>Zoono</i> B22-1402A. Biofilms grown on 96-pin lids were more quickly eradicated than those grown in the CDC biofilm reactor.