Antimicrobial peptides (AMPs) are promising alternatives to antibiotics for treatment of antimicrobial resistant (AMR) bacterial infections. However, their narrow therapeutic window due to in vivo... Show moreAntimicrobial peptides (AMPs) are promising alternatives to antibiotics for treatment of antimicrobial resistant (AMR) bacterial infections. However, their narrow therapeutic window due to in vivo toxicity and limited stability hampers their clinical use. Here, we evaluated encapsulation of two amphiphilic AMPs, SAAP-148 and snake cathelicidin Ab-Cath, into oleyl-modified hyaluronic acid (OL-HA) nanogels to improve their selectivity index. The AMP-loaded OL-HA nanogels ranged 181–206 nm in size with a PDI of 0.2, highly negative surface charge (−47 to −48 mV) and moderate encapsulation efficiency (53–63%). The AMP-loaded OL-HA nanogels displayed similar activity in vitro as AMP solutions against AMR Staphylococcus aureus and Acinetobacter baumannii, with a dose-dependent effect over time. Importantly, the AMP-loaded OL-HA nanogels showed decreased cytotoxicity towards human erythrocytes and primary skin fibroblast, thereby improving the selectivity index of SAAP-148 and Ab-Cath by 2- and 16.8-fold, respectively. Particularly, the selectivity of Ab-Cath-loaded OL-HA nanogels has great clinical potential, with an index that reached ≥ 300 for S. aureus and ≥ 3000 for A. baumannii. These findings indicate that OL-HA nanogels are a promising drug delivery system to reduce the cytotoxicity of AMPs without substantially affecting their antimicrobial activity, thereby increasing their selectivity index and potential as therapeutics to combat AMR bacterial infections. Show less
A prosthetic joint infection (PJI) is a severe complication after arthroplasty. From the current thesis, three main conclusion can be drawn regarding diagnosis and treamtent of PJI. (a) Accurate... Show moreA prosthetic joint infection (PJI) is a severe complication after arthroplasty. From the current thesis, three main conclusion can be drawn regarding diagnosis and treamtent of PJI. (a) Accurate self-monitoring of postoperative wounds after joint implantation helped elucidate the course of wound leakage and its association with acute prosthetic joint infections. (b) The collection of clinical data on different antimicrobial treatment strategies provided insight into the effectiveness of different treatment options for patients with a prosthetic joint infection. In this thesis, we report that personalized antimicrobial treatment for prosthetic joint infections is possible without compromising the effectiveness of treatment. (c) this thesis describes the role and importance of new anti-persister drugs against biofilm-associated infections. We developed a biofilm model that closely resembles the clinic of a prosthetic joint infection. Based on the results described in this thesis, future research will be aimed at better understanding the pathogenesis of biofilms. This should ultimately lead to better treatment options for patients with a prosthetic joint infection. Show less
Bacterial infections are becoming harder-to-treat with current antibiotics, due to antimicrobial resistance and biofilm-formation. Therefore, there is an urgent need for novel antibacterial agents... Show moreBacterial infections are becoming harder-to-treat with current antibiotics, due to antimicrobial resistance and biofilm-formation. Therefore, there is an urgent need for novel antibacterial agents and antimicrobial peptides (AMPs) may fulfill this role. Herein, three strategies were explored for optimization of our lead AMP SAAP-148 to combat bacterial infections: i) chemical lead-optimization, ii) combination therapy with other antimicrobial agents and iii) innovative AMP delivery systems. The latter strategy was also applied to another promising AMP, the snake cathelicidin Ab-Cath. First, we demonstrated that conjugation of short polyethylene glycol chains to SAAP-148 reduced the peptide’s cytotoxicity and remarkably improved its ability to modulate the immune system to a more pro-inflammatory subset. Second, it was shown that combinations of SAAP-148 and novel antibiotic halicin were more effective than single agent treatment against planktonic bacteria of specific resistant bacterial strains, also in clinically relevant cell models. Third, we demonstrated that hyaluronic acid-based nanogels allow for efficient encapsulation of SAAP-148 and Ab-Cath, thereby improving the selectivity index of both peptides by maintaining antimicrobial activities against resistant bacteria and reducing cytotoxic activities against mammalian cells. Thus, the findings described in this thesis contribute to the development of SAAP-148 and Ab-Cath as therapeutics to combat bacterial infections. Show less
Background: Accurate determination of the efficacy of antimicrobial agents requires neutralization of residual antimicrobial activity in the samples before microbiological assessment of the number... Show moreBackground: Accurate determination of the efficacy of antimicrobial agents requires neutralization of residual antimicrobial activity in the samples before microbiological assessment of the number of surviving bacteria. Sodium polyanethol sulfonate (SPS) is a known neutralizer for the antimicrobial activity of aminoglycosides and polymyxins. In this study, we evaluated the ability of SPS to neutralize residual antimicrobial activity of antimicrobial peptides [SAAP-148 and pexiganan; 1% (wt/v) in PBS], antibiotics [mupirocin (Bactroban) and fusidic acid (Fucidin) in ointments; 2% (wt/wt))] and disinfectants [2% (wt/wt) silver sulfadiazine cream (SSD) and 0.5% (v/v) chlorhexidine in 70% alcohol].Methods: Homogenates of human skin models that had been exposed to various antimicrobial agents for 1 h were pipetted on top of Methicillin-resistant Staphylococcus aureus (MRSA) on agar plates to determine whether the antimicrobial agents display residual activity.To determine the optimal concentration of SPS for neutralization, antimicrobial agents were mixed with PBS or increasing doses of SPS in PBS (0.05-1% wt/v) and then 105 colony forming units (CFU)/mL MRSA were added. After 30min incubation, the number of viable bacteria was assessed. Next, the in vitro efficacy of SAAP-148 against various gram-positive and gram-negative bacteria was determined using PBS or 0.05% (wt/v) SPS immediately after 30 min incubation of the mixture. Additionally, ex vivo excision wound models were inoculated with 105 CFU MRSA for 1 h and exposed to SAAP-148, pexiganan, chlorhexidine or PBS for 1 h. Subsequently, samples were homogenized in PBS or 0.05% (wt/v) SPS and the number of viable bacteria was assessed.Results: All tested antimicrobials displayed residual activity in tissue samples, resulting in a lower recovery of surviving bacteria on agar. SPS concentrations at >= 0.05% (wt/v) were able to neutralize the antimicrobial activity of SAAP-148, pexiganan and chlorhexidine, but not of SSD, Bactroban and Fucidin. Finally, SPS-neutralization in in vitro and ex vivo efficacy tests of SAAP-148, pexiganan and chlorhexidine against gram-positive and gram-negative bacteria resulted in significantly higher numbers of CFU compared to control samples without SPS-neutralization.Conclusions: SPS was successfully used to neutralize residual activity of SAAP-148, pexiganan and chlorhexidine and this prevented an overestimation of their efficacy. Show less
Background: We investigated the efficacy of a synthetic antimicrobial peptide SAAP-148, which was shown to be effective against Methicillin-resistant Staphylococcus aureus (MRSA) on tape-stripped... Show moreBackground: We investigated the efficacy of a synthetic antimicrobial peptide SAAP-148, which was shown to be effective against Methicillin-resistant Staphylococcus aureus (MRSA) on tape-stripped mice skin. Unexpectedly, SAAP-148 was not effective against MRSA in our pilot study using rats with excision wounds. Therefore, we investigated factors that might have contributed to the poor efficacy of SAAP-148. Subsequently, we optimised the protocol and assessed the efficacy of SAAP-148 in an adapted rat study.Methods: We incubated 100 mu L of SAAP-148 with 1 cm(2) of a wound dressing for 1 h and determined the unabsorbed volume of peptide solution. Furthermore, 10(5) colony forming units (CFU)/mL MRSA were exposed to increasing dosages of SAAP-148 in 50% (v/v) human plasma, eschar- or skin extract or PBS. After 30 min incubation, the number of viable bacteria was determined. Next, ex vivo skin models were inoculated with MRSA for 1 h and exposed to SAAP-148. Finally, excision wounds on the back of rats were inoculated with 10(7) CFU MRSA overnight and treated with SAAP-148 for 4 h or 24 h. Subsequently, the number of viable bacteria was determined.Results: Contrary to Cuticell, Parafilm and Tegaderm film, < 20% of peptide solution was recovered after incubation with gauze, Mepilex border and Opsite Post-op. Furthermore, in plasma, eschar- or skin extract > 20-fold higher dosages of SAAP-148 were required to achieve a 2-log reduction (LR) of MRSA versus SAAP-148 in PBS. Exposure of ex vivo models to SAAP-148 for 24 h resulted in a 4-fold lower LR than a 1 h or 4 h exposure period. Additionally, SAAP-148 caused a 1.3-fold lower mean LR at a load of 10(7) CFU compared to 10(5) CFU MRSA. Moreover, exposure of ex vivo excision wound models to SAAP-148 resulted in a 1.5-fold lower LR than for tape-stripped skin. Finally, SAAP-148 failed to reduce the bacterial counts in an adapted rat study.Conclusions: Several factors, such as absorption of SAAP-148 by wound dressings, components within wound exudates, re-colonisation during the exposure of SAAP-148, and a high bacterial load may contribute to the poor antimicrobial effect of SAAP-148 against MRSA in the rat model. Show less
Nibberinga, P.H.; Goblyos, A.; Adriaans, A.E.; Cordfunke, R.A.; Ravensbergen, B.; Rietveld, M.H.; ... ; Ghalbzouri, A. el 2019
Skin bacterial colonization/infection is a frequent cause of morbidity in patients with chronic wounds and allergic/inflammatory skin diseases. This study aimed to develop a novel approach to... Show moreSkin bacterial colonization/infection is a frequent cause of morbidity in patients with chronic wounds and allergic/inflammatory skin diseases. This study aimed to develop a novel approach to eradicate meticillin-resistant Staphylococcus aureus (MRSA) from human skin. To achieve this, the stability and antibacterial activity of the novel LL-37-derived peptide P10 in four ointments was compared. Results indicate that P10 is chemically stable and antibacterial in hypromellose gel and Softisan-containing cream, but not in Cetomacrogol cream (with or without Vaseline), at 4 degrees C for 16 months. Reduction in MRSA counts on Leiden human epidermal models (LEMs) by P10 in hypromellose gel was greater than that of the peptide in Cetomacrogol cream or phosphate buffered saline. P10 did not show adverse effects on LEMs irrespective of the ointment used, while Cetomacrogol with Vaseline and Softisan cream, but not hypromellose gel or Cetomacrogol cream, destroyed MRSA-colonized LEMs. Taking all this into account, P10 in hypromellose gel dose-dependently reduced MRSA colonizing the stratum corneum of the epidermis as well as biofilms of this bacterial strain on LEMs. Moreover, P10 dose-dependently reduced MRSA counts on ex-vivo human skin, with P10 in hypromellose gel being more effective than P10 in Cetomacrogol and Softisan creams. P10 in hypromellose gel is a strong candidate for eradication of MRSA from human skin. (C) 2019 Elsevier B.V. and International Society of Chemotherapy. All rights reserved. Show less
The disease is characterized by a progressive and largely irreversible decline in lung function, which is associated with long-term airway exposures to cytotoxic particles and gasses, such as... Show moreThe disease is characterized by a progressive and largely irreversible decline in lung function, which is associated with long-term airway exposures to cytotoxic particles and gasses, such as cigarette smoke. Microbial colonization and infections are an important pathophysiological aspect in COPD patients. However, the underlying mechanisms linking smoking with microbial colonization and infections in COPD are incompletely understood. The airway epithelium is the first target of inhaled cigarette smoke. Furthermore, epithelial cells are the first defense lining of the respiratory tract that prevents microbial colonization and infections. Therefore, alterations in host defense and airway epithelial remodeling may contribute to COPD development and progression. In this thesis, studies are presented in which the impact of cigarette smoke exposure and COPD disease status on the innate host defense functions of the airway epithelium are explored. This was done by using cell culture experiments in which the effect of cigarette smoke was examined, or in which epithelial cultures of COPD patients and non-COPD (ex)smokers were compared. Show less
Infection of burn wounds remains the leading cause of death in burn patients. Topical treatment of such infections with conventional antibiotics is often unsuccessful due to the presence of... Show moreInfection of burn wounds remains the leading cause of death in burn patients. Topical treatment of such infections with conventional antibiotics is often unsuccessful due to the presence of drug-resistant bacteria and/or to the formation of bacterial biofilms. Taken together there is a clear need for novel antimicrobial agents with modes of action different that of current antibiotics. Identification of new synthetic peptide antibiotics for topical use holds a promising approach. In vitro skin models pose many similar properties as normal human skin, and are often used in laboratory settings. In this thesis in vitro models were used to study the effect of colonization and infection of healthy skin, (thermally) wounded skin (chapter 2), mucosal membranes (chapter 3) and skin with characteristics of atopic dermatitis (chapter 6). In addition, the difference in bacterial biofilm formation on biotic (in vitro skin models) versus a-biotic surfaces (polystyrene) was investigated (chapter 7). Finally, skin models were used to identify potent synthetic antimicrobial peptides against drug-resistant bacteria such as Staphylococcus aureus (chapter 3,4). These peptides proved to be effective when applied topically in saline, but also in a hydrogel (chapter 5). Show less
