Tannin derived materials can block swarming motility and enhance biofilm formation in Pseudomonas aeruginosa.

Surface-associated swarming motility is implicated in enhanced bacterial spreading and virulence, hence it follows that anti-swarming effectors could have clinical benefits. When investigating potential applications of anti-swarming materials it is important to consider whether the lack of swarming corresponds with an enhanced sessile biofilm lifestyle and resistance to antibiotics. In this study, well-defined tannins present in multiple plant materials (tannic acid (TA) and epigallocathecin gallate (EGCG)) and undefined cranberry powder (CP) were found to block swarming motility and enhance biofilm formation and resistance to tobramycin in Pseudomonas aeruginosa. In contrast, gallic acid (GA) did not completely block swarming motility and did not affect biofilm formation or tobramycin resistance. These data support the theory that nutritional conditions can elicit an inverse relationship between swarming motility and biofilm formation capacities. Although anti-swarmers exhibit the potential to yield clinical benefits, it is important to be aware of possible implications regarding biofilm formation and antibiotic resistance.