Human Host Defense Peptide LL-37 Prevents Bacterial Biofilm Formation

Abstract

The ability to form biofilms is a critical factor in chronic infections by Pseudomonas aeruginosa and has made this bacterium a model organism with respect to biofilm formation. This study describes a new, previously unrecognized role for the human cationic host defense peptide LL-37. In addition to its key role in modulating the innate immune response and weak antimicrobial activity, LL-37 potently inhibited the formation of bacterial biofilms in vitro. This occurred at the very low and physiologically meaningful concentration of 0.5 g/ml, far below that required to kill or inhibit growth (MIC ‫؍‬ 64 g/ml). LL-37 also affected existing, pregrown P. aeruginosa biofilms. Similar results were obtained using the bovine neutrophil peptide indolicidin, but no inhibitory effect on biofilm formation was detected using subinhibitory concentrations of the mouse peptide CRAMP, which shares 67% identity with LL-37, polymyxin B, or the bovine bactenecin homolog Bac2A. Using microarrays and follow-up studies, we were able to demonstrate that LL-37 affected biofilm formation by decreasing the attachment of bacterial cells, stimulating twitching motility, and influencing two major quorum sensing systems (Las and Rhl), leading to the downregulation of genes essential for biofilm development.

Subinhibitory concentrations of the cationic antimicrobial peptide colistin induce the pseudomonas quinolone signal in Pseudomonas aeruginosa

“…Plate assays reveal increased expression of lasIR in E. coli in the presence of both colistin and polymyxin B, while expression is unchanged in liquid cultures (Goh et al, 2002). In contrast, several recent studies have reported downregulation of the rhlIR and lasIR N-acylhomoserine lactone signalling systems in P. aeruginosa in response to sublethal concentrations of LL-37, azithromycin, ceftazidime and ciprofloxacin (Nalca et al, 2006;Overhage et al, 2008;Skindersoe et al, 2008). Therefore, the emerging model is one where subinhibitory concentrations of antibiotics elicit a niche-specific response in bacteria, which may contribute to adaptation within a natural ecosystem.…”

Anti-Staphylococcal Biofilm Effects of Human Cathelicidin Peptides

“…11 The antibiofilm activity of human LL-37 against Pseudomonas aeruginosa was first described in 2008. 12 LL-37 also inhibits the attachment and biofilm formation of Staphylococcus epidermidis 13 and S. aureus 14 at low concentrations. In addition, the LL-37 molecule made using D-amino acids is also effective in preventing biofilm formation.…”

New trends in peptide-based anti-biofilm strategies: a review of recent achievements and bioinformatic approaches

“…This is the case for the synthetic AMP NA-CATH:ATRA1-ATRA1 and the natural AMP LL-37, both from the cathelicidin family, that are effective against Staphylococcus aureus and Pseudomonas aeruginosa biofilms, respectively. These AMPs are thought to act internally on the bacterial cells, affecting gene expression essential for the development of biofilms (Overhage et al 2008;Dean et al 2011). In P. aeruginosa, the AMP LL-37 also alters the expression of biofilm related genes, such as Type IV pili, rhamnolipid and Las quorum sensing systems at sub-antimicrobial levels, and genes associated with the assembly of flagella, involved in initial adherence during biofilm formation, were found to be down regulated (Overhage et al 2008).…”

“…These AMPs are thought to act internally on the bacterial cells, affecting gene expression essential for the development of biofilms (Overhage et al 2008;Dean et al 2011). In P. aeruginosa, the AMP LL-37 also alters the expression of biofilm related genes, such as Type IV pili, rhamnolipid and Las quorum sensing systems at sub-antimicrobial levels, and genes associated with the assembly of flagella, involved in initial adherence during biofilm formation, were found to be down regulated (Overhage et al 2008). LL-37 is also capable of inhibiting initial biofilm attachment (by 58-62%), suggesting that peptides of this kind may be interacting with bacterial adhesins as part of their anti-biofilm mechanism (Dean et al 2011).…”