A short artificial antimicrobial peptide shows potential to prevent or treat bone infections

Abstract

Infection of bone is a severe complication due to the variety of bacteria causing it, their resistance against classical antibiotics, the formation of a biofilm and the difficulty to eradicate it. Antimicrobial peptides (AMPs) are naturally occurring peptides and promising candidates for treatment of joint infections. This study aimed to analyze the effect of short artificial peptides derived from an optimized library regarding (1) antimicrobial effect on different bacterial species, (2) efficacy on biofilms, and (3) effect on osteoblast-like cells. Culturing the AMP-modifications with Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus (including clinical isolates of MRSA and MSSA) and Staphylococcus epidermidis identified one candidate that was most effective against all bacteria. This AMP was also able to reduce biofilm as demonstrated by FISH and microcalorimetry. Osteoblast viability and differentiation were not negatively affected by the AMP. A cation concentration comparable to that physiologically occurring in blood had almost no negative effect on AMP activity and even with 10% serum bacterial growth was inhibited. Bacteria internalized into osteoblasts were reduced by the AMP. Taken together the results demonstrate a high antimicrobial activity of the AMP even against bacteria incorporated in a biofilm or internalized into cells without harming human osteoblasts.Infections of bone are a severe complication and can result in a long-term treatment. Infected/contaminated material (tissue and implant) must be removed and the infection cleared. Staphylococcus aureus is the predominant bacteria identified in fracture-fixation device associated infections (30%) followed by coagulase-negative staphylococci (22%), but also Gram-negative bacteria, enterococci, streptococci and other species may be isolated 1 . The interaction of S. aureus with bone or especially osteoblasts is well investigated 2 . For example, S. aureus expresses several molecules (collagen adhesin, bone sialoprotein binding protein, MHC II analog protein) that support the binding with proteins of the extracellular matrix of bone, but also induces the secretion of inflammatory factors and chemokines, and can induce apoptosis. A mechanism that allows S. aureus to persist protected from the immune system and most antibiotics is the internalization into host cells, especially osteoblast 3 . Within the last decades the number of resistant bacteria increased, resulting in more challenges for the treatment. Facing the impact of resistant bacteria on the human health and the health care systems, antimicrobial resistance (AMR) is identified as one of the major health problems 4 resulting in the endorsement of a global action plan by the World Health Organization to tackle antimicrobial resistance. Besides the need to increase the awareness to this problem and the improvement of the antibiotic use, new antimicrobial active drugs must be developed. An interesting group of antimicrobial active drugs are antimicrobial pep...

Antimicrobial peptides – Advances in development of therapeutic applications

“…Bormann et al reported high antimicrobial potency of some AMPs against bacteria both incorporated in a biofilm or internalized into cells with no harm to human osteoblasts [ 113 ]. Furthermore, Hui Li et al demonstrated that KR-12 - a fragment of human antimicrobial peptide cathelicidin LL-37 improves the osteogenic differentiation of human bone marrow mesenchymal stem cells via stimulating BMP/SMAD signaling [ 114 ].…”

Lactoferrin Functionalized Biomaterials: Tools for Prevention of Implant-Associated Infections

“…In implant-associated infection several factors are involved such as surgical procedure, microorganisms, host, type of the implant and antimicrobial prophylaxis [ 30 , 31 ]. The predominant microbial agent isolated from implant-associated infection is Staphylococcus aureus (30%), followed by coagulase-negative staphylococci (22%), but Gram-negative bacteria, enterococci, streptococci and other species may be isolated [ 32 , 33 ]. In conformity with current knowledge, biofilm formation presumably is the most critical pathogenic event in implant-associated infection.…”

“…The implants protect the microorganisms from the host immune system and systemic antibiotics [ 30 ]. Bacterial adhesion to the implant surface—and colonization of the tissue surrounding the implant secretion of exopolysaccharides, aggregation in a slime layer and further differentiation and biofilm formation—are the most significant steps in implant infection [ 2 , 32 , 33 , 34 , 35 ]. Bacterial adhesion to the surfaces is generally nonspecific and it is produced by unspecific forces, namely, van der Wall, acid base or electrostatic interaction [ 36 ].…”

“…AMPs interrelate with certain specific constituents of the bacterial plasma membrane resulting in depolarization, destabilization, and/or disruption, leading to bacterial cell destruction [ 24 ]. AMPs are the host defense, naturally occurring peptides [ 33 , 49 ] and have been revealed to exhibit a broad spectrum of activities against Gram-positive and Gram-negative bacteria, fungi and viruses [ 61 , 74 ]. They have the capacity to neutralize virulence factors released by pathogens and also modulate the host immune response [ 75 , 76 ] and can also effectively attack bacteria within a biofilm (Ageitos et al 2016).…”

“…More than 2700 different AMPs have been described to date [ 33 , 49 ]. Bacteriocins are bacterial AMPs, classified into class I bacteriocins known lantibiotics and class II bacteriocin/non-lantibiotics [ 77 ].…”