Development of novel antimicrobial agents is a top priority in the fight against multidrug-resistant (MDR) and persistent bacteria. We developed a panel of synthetic antimicrobial and antibiofilm peptides (SAAPs) with enhanced antimicrobial activities compared to the parent peptide, human antimicrobial peptide LL-37. Our lead peptide SAAP-148 was more efficient in killing bacteria under physiological conditions in vitro than many known preclinical- and clinical-phase antimicrobial peptides. SAAP-148 killed MDR pathogens without inducing resistance, prevented biofilm formation, and eliminated established biofilms and persister cells. A single 4-hour treatment with hypromellose ointment containing SAAP-148 completely eradicated acute and established, biofilm-associated infections with methicillin-resistant Staphylococcus aureus and MDR Acinetobacter baumannii from wounded ex vivo human skin and murine skin in vivo. Together, these data demonstrate that SAAP-148 is a promising drug candidate in the battle against antibiotic-resistant bacteria that pose a great threat to human health.

With the rise in prevalence of antibioticresistant bacteria, honey is increasingly valued for its antibacterial activity. To characterize all bactericidal factors in a medical‐grade honey, we used a novel approach of successive neutralization of individual honey bactericidal factors. All bacteria tested, including Bacillus subtilis , methicillin‐resistant Staphylococcus aureus , extended‐spectrum ß‐lactamase producing Escherichia coli , ciprofloxacin‐resistant Pseudomonas aeruginosa , and vancomycin‐resistant Enterococcus faecium , were killed by 10–20% (v/v) honey, whereas ≥40% (v/v) of a honey‐equivalent sugar solution was required for similar activity. Honey accumulated up to 5.62 ± 0.54 mM H ₂ O ₂ and contained 0.25 ± 0.01 mM methylglyoxal (MGO). After enzymatic neutralization of these two compounds, honey retained substantial activity. Using B. subtilis for activity‐guided isolation of the additional antimicrobial factors, we discovered bee defensin‐1 in honey. After combined neutralization of H ₂ O ₂ , MGO, and bee defensin‐1, 20% honey had only minimal activity left, and subsequent adjustment of the pH of this honey from 3.3 to 7.0 reduced the activity to that of sugar alone. Activity against all other bacteria tested depended on sugar, H ₂ O ₂ , MGO, and bee defensin‐1. Thus, we fully characterized the antibacterial activity of medical‐grade honey.—Kwakman, P. H. S., te Velde, A. A., de Boer, L., Speijer, D., Vandenbroucke‐Grauls, C. M.J. E., Zaat, S. A.J. How honey kills bacteria. FASEB J. 24, 2576–2582 (2010). www.fasebj.org

The antibacterial activity of honey has been known since the 19th century. Recently, the potent activity of honey against antibiotic‐resistant bacteria has further increased the interest for application of honey, but incomplete knowledge of the antibacterial activity is a major obstacle for clinical applicability. The high sugar concentration, hydrogen peroxide, and the low pH are well‐known antibacterial factors in honey and more recently, methylglyoxal and the antimicrobial peptide bee defensin‐1 were identified as important antibacterial compounds in honey. The antibacterial activity of honey is highly complex due to the involvement of multiple compounds and due to the large variation in the concentrations of these compounds among honeys. The current review will elaborate on the antibacterial compounds in honey. We discuss the activity of the individual compounds, their contribution to the complex antibacterial activity of honey, a novel approach to identify additional honey antibacterial compounds, and the implications of the novel developments for standardization of honey for medical applications. © 2011 IUBMB IUBMB Life, 2011.s

Antibacterial proteins are components of the innate immune system found in many organisms and produced by a variety of cell types. Human blood platelets contain a number of antibacterial proteins in their α-granules that are released upon thrombin activation. The present study was designed to purify these proteins obtained from human platelets and to characterize them chemically and biologically. Two antibacterial proteins were purified from platelet granules in a two-step protocol using cation exchange chromatography and continuous acid urea polyacrylamide gel electrophoresis and were designated thrombocidin (TC)-1 and TC-2. Characterization of these proteins using mass spectrometry and N-terminal sequencing revealed that TC-1 and TC-2 are variants of the CXC chemokines neutrophil-activating peptide-2 and connective tissue-activating peptide-III, respectively. TC-1 and TC-2 differ from these chemokines by a C-terminal truncation of 2 amino acids. Both TCs, but not neutrophil-activating peptide-2 and connective tissue-activating peptide-III, were bactericidal for Bacillus subtilis,Escherichia coli, Staphylococcus aureus, andLactococcus lactis and fungicidal for Cryptococcus neoformans. Killing of B. subtilis by either TC appeared to be very rapid. Because TCs were unable to dissipate the membrane potential of L. lactis, the mechanism of TC-mediated killing most probably does not involve pore formation.

Honey is increasingly valued for its antibacterial activity, but knowledge regarding the mechanism of action is still incomplete. We assessed the bactericidal activity and mechanism of action of Revamil® source (RS) honey and manuka honey, the sources of two major medical-grade honeys. RS honey killed Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa within 2 hours, whereas manuka honey had such rapid activity only against B. subtilis. After 24 hours of incubation, both honeys killed all tested bacteria, including methicillin-resistant Staphylococcus aureus, but manuka honey retained activity up to higher dilutions than RS honey. Bee defensin-1 and H₂O₂ were the major factors involved in rapid bactericidal activity of RS honey. These factors were absent in manuka honey, but this honey contained 44-fold higher concentrations of methylglyoxal than RS honey. Methylglyoxal was a major bactericidal factor in manuka honey, but after neutralization of this compound manuka honey retained bactericidal activity due to several unknown factors. RS and manuka honey have highly distinct compositions of bactericidal factors, resulting in large differences in bactericidal activity.

Over the past decades the use of medical devices, such as catheters, artificial heart valves, prosthetic joints and other implants, has grown significantly. Despite continuous improvements in device design, surgical procedures and wound care, biomaterial-associated infections (BAI) are still a major problem in modern medicine. Conventional antibiotic treatment often fails due to the low levels of antibiotic at the site of infection. The presence of biofilms on the biomaterial and/or the multidrug-resistant phenotype of the bacteria further impair the efficacy of antibiotic treatment. Removal of the biomaterial is then the last option to control the infection. Clearly, there is a pressing need for alternative strategies to prevent and treat BAI. Synthetic antimicrobial peptides (AMPs) are considered promising candidates as they are active against a broad spectrum of (antibiotic-resistant) planktonic bacteria and biofilms. Moreover, bacteria are less likely to develop resistance to these rapidly-acting peptides. In this review we highlight the four main strategies, three of which applying AMPs, in biomedical device manufacturing to prevent BAI. The first involves modification of the physicochemical characteristics of the surface of implants. Immobilization of AMPs on surfaces of medical devices with a variety of chemical techniques is essential in the second strategy. The main disadvantage of these two strategies relates to the limited antibacterial effect in the tissue surrounding the implant. This limitation is addressed by the third strategy that releases AMPs from a coating in a controlled fashion. Lastly, AMPs can be integrated in the design and manufacturing of additively manufactured / 3D-printed implants, owing to the physicochemical characteristics of the implant material and the versatile manufacturing technologies compatible with antimicrobials incorporation. These novel technologies utilizing AMPs will contribute to development of novel and safe antimicrobial medical devices, reducing complications and associated costs of device infection.