Phytopigment Alizarin Inhibits Multispecies Biofilm Development by , , and .

Acne vulgaris is a common chronic inflammatory skin disease involving with other skin commensals such as and in the anaerobic and lipid-rich conditions of pilosebaceous units. These microbes readily form multispecies biofilms that are tolerant of traditional antibiotics as well as host immune systems. The phytopigment alizarin was previously found to prevent biofilm formation by and strains under aerobic conditions. Hence, we hypothesized that alizarin might control and multispecies biofilm development. We found that under anaerobic conditions, alizarin efficiently inhibited single biofilm formation and multispecies biofilm development by , , and without inhibiting planktonic cell growth. Alizarin increased the hydrophilicities of and cells, decreased lipase production by , diminished agglutination by and inhibited the aggregation of cells. Furthermore, the co-administration of alizarin and antibiotics enhanced the antibiofilm efficacies of alizarin against . A transcriptomic study showed that alizarin repressed the transcriptions of various biofilm-related genes such as lipase, hyaluronate lyase, adhesin/invasion-related, and virulence-related genes of . Furthermore, alizarin at 100 µg/mL prevented biofilm development on porcine skin. Our results show that alizarin inhibits multispecies biofilm development by acne-causing microbes and suggest it might be a useful agent for treating or preventing -causing skin diseases.