Breaking the Barrier: Polyproline Peptides Disrupt the Matrix of Hypervirulent Klebsiella pneumoniae Biofilms to Release Bacteria from their Protective Barrier.

Klebsiella pneumoniae is a dangerous pathogen that has gained much notoriety due to its extreme rate of resistance development. K. pneumoniae acute and chronic wound treatment is complicated by the presence of biofilm formation, which contributes to drug resistance, persistence, tolerance, and slow wound healing. In addition to wound infections, biofilm formation abilities of K. pneumoniae lead to persistent, drug resistant catheter infections. Antimicrobial peptides have shown promise in recent years as a topical treatment and as a device coating to eradicate drug resistant K. pneumoniae. Previous work from our lab revealed a mechanism used by antimicrobial peptides to disrupt the capsule of K. pneumoniae. Recently, we have found that a polyproline peptide bac7 (1-35) can disrupt pre-formed biofilms of hypervirulent K. pneumoniae. Using confocal microscopy of K. pneumoniae NTUH K2044 biofilms with bacteria constitutively expressing GFP and matrix polysaccharides labeled with Texas red tagged Concanavalin A, we show bac7 (1-35) decreases the biofilm matrix material and releases the cells from their protective encasing. Live/dead staining images then revealed the dispersed cells were eradicated by the antimicrobial properties of the peptide. Interestingly, bac7 (1-35) treatment was found to decrease the mucoid phenotype of this species that is provided by capsular polysaccharides. Our results show that in addition to capsular polysaccharides, biofilm matrix polysaccharides are targeted by peptides to potentially sensitize hypervirulent K. pneumoniae to the host immune system and antibiotic therapies.