<i>Enterococcus faecalis</i> inhibits <i>Klebsiella pneumoniae</i> growth in polymicrobial biofilms in a glucose-enriched medium

Abstract

Catheter-related urinary tract infections are one of the most common biofilm-associated diseases. Within biofilms, bacteria cooperate, compete, or have neutral interactions. This study aimed to investigate the interactions in polymicrobial biofilms of <i>Klebsiella pneumoniae</i> and <i>Enterococcus faecalis</i>, two of the most common uropathogens. Although <i>K. pneumoniae</i> was the most adherent strain, it could not maintain dominance in the polymicrobial biofilm due to the lactic acid produced by <i>E. faecalis</i> in a glucose-enriched medium. This result was supported by the use of <i>E. faecalis</i> V583 <i>ldh-1/ldh-2</i> double mutant (non-producer of lactic acid), which did not inhibit the growth of <i>K. pneumoniae</i>. Lyophilized cell-free supernatants obtained from <i>E. faecalis</i> biofilms also showed antimicrobial/anti-biofilm activity against <i>K. pneumoniae</i>. Conversely, there were no significant differences in planktonic polymicrobial cultures. In summary, <i>E. faecalis</i> modifies the pH by lactic acid production in polymicrobial biofilms, which impairs the growth of <i>K. pneumoniae</i>.