Activity of daptomycin on biofilms produced on a plastic support by Staphylococcus spp

Daptomycin as an option for lock therapy: a systematic literature review

Aim: To review preclinical and clinical data relevant to daptomycin lock therapy in catheter-related bloodstream infection (CRBSI). Methods: Systematic review in PubMed, Scopus and clinical trial registries. Results: Preclinical data demonstrate daptomycin lock solution stability and compatibility with heparin, good biofilm penetration, bactericidal activity against biofilm-embedded bacteria, and high efficacy in vitro and in animal catheter infection models. Clinical data remain limited (two case reports and five case series totaling n = 65 CRBSI episodes), albeit promising (successful catheter salvage in about 80% of cases). Conclusion: Despite theoretical advantages of daptomycin, clinical data remain scarce. Comparative studies versus alternative lock solutions are needed, as well as studies to define optimal daptomycin lock regimen (including optimal concentration, dwell time and lock duration).

Novel approaches for the treatment of methicillin-resistant Staphylococcus aureus: Using nanoparticles to overcome multidrug resistance

Methicillin-resistant Staphylococcus aureus (MRSA) causes serious infections in both community and hospital settings, with high mortality rates. Treatment of MRSA infections is challenging because of the rapidly evolving resistance mechanisms combined with the protective biofilms of S. aureus. Together, these characteristic resistance mechanisms continue to render conventional treatment modalities ineffective. The use of nanoformulations with unique modes of transport across bacterial membranes could be a useful strategy for disease-specific delivery. In this review, we summarize treatment approaches for MRSA, including novel techniques in nanoparticulate designing for better therapeutic outcomes; and facilitate an understanding that nanoparticulate delivery systems could be a robust approach in the successful treatment of MRSA.

The biofilm eradication activity of acetic acid in the management of periprosthetic joint infection

Objectives

Periprosthetic joint infection following joint arthroplasty surgery is one of the most feared complications. The key to successful revision surgery for periprosthetic joint infections, regardless of treatment strategy, is a thorough deep debridement. In an attempt to limit antimicrobial and disinfectant use, there has been increasing interest in the use of acetic acid as an adjunct to debridement in the management of periprosthetic joint infections. However, its effectiveness in the eradication of established biofilms following clinically relevant treatment times has not been established. Using an in vitro biofilm model, this study aimed to establish the minimum biofilm eradication concentration (MBEC) of acetic acid following a clinically relevant treatment time.

Materials and Methods

Using a methicillin-sensitive Staphylococcus aureus (MSSA) reference strain and the dissolvable bead assay, biofilms were challenged by 0% to 20% acetic acid (pH 4.7) for ten minutes, 20 minutes, 180 minutes, and 24 hours.

Results

The MBEC of acetic acid was found to be: 15%, 11%, 3.2%, and 0.8% following a ten-minute, 20-minute, 180-minute, and 24-hour treatment, respectively.

Conclusion

This study found that the MBEC of acetic acid following a 10- or 20-minute treatment time exceeded its safety threshold, making these concentrations unsuitable as a topical debridement adjunct. However, a clinically acceptable concentration (5%) was still found to eliminate 96.1% of biofilm-associated MSSA following a 20-minute treatment time.

Cite this article: S. T. J. Tsang, P. J. Gwynne, M. P. Gallagher, A. H. R. W. Simpson. The biofilm eradication activity of acetic acid in the management of periprosthetic joint infection. Bone Joint Res 2018;7:517–523. DOI: 10.1302/2046-3758.78.BJR-2018-0045.R1

A Long-Term Retrospective Review of 5 Cases using Daptomycin for Prosthetic Device Infections after Surgery

Purpose

To review the antimicrobial possibilities for limb-sparing due to infectious complications after surgery in patients diagnosed with osteosarcoma and with implantation of prosthetic devices.

Patients and Progress

After several episodes of relapsing infection or even re-infection and failure of previous therapies, 5 patients (2 young, female / 1 young, male / 2 middle-aged, female) were subject to a long-term ambulatory regimen consisting of intravenous administration of daptomycin.

Results

Showed improved outcome with preservation of the limbs or devices involved.

Conclusion

Five patients with post-operative gram-positive suspected infections of prosthetic devices that were unresponsive to a variety of other antibiotics and combinations appeared to respond to compassionate use of daptomycin. Its effectiveness is probably due to its activity against biofilm-producing microorganisms. Controlled, double-blind randomized trials are needed to confirm the potential of daptomycin in such patients.

Identification of N-Arylated NH125 Analogues as Rapid Eradicating Agents against MRSA Persister Cells and Potent Biofilm Killers of Gram-Positive Pathogens

Bacterial biofilms housing dormant persister cells are innately tolerant to antibiotics and disinfectants, yet several membrane-active agents are known to eradicate tolerant bacterial cells. NH125, a membrane-active persister killer and starting point for development, led to the identification of two N-arylated analogues (1 and 2) that displayed improved biofilm eradication potencies compared to the parent compound and rapid persister-cell-killing activities in stationary cultures of methicillin-resistant Staphylococcus aureus (MRSA). We found 1 and 2 to be superior to other membrane-active agents in biofilm eradication assays, with 1 demonstrating minimum biofilm eradication concentrations (MBEC) of 23.5, 11.7, and 2.35 μm against MRSA, methicillin-resistant Staphylococcus epidermidis (MRSE), and vancomycin-resistant Enterococcus faecium (VRE) biofilms, respectively. We tested our panel of membrane-active agents against MRSA stationary cultures and found 1 to rapidly eradicate MRSA stationary cells by 4 log units (99.99 %) in 30 min. The potent biofilm eradication and rapid persister-cell-killing activities exhibited by N-arylated NH125 analogues could have significant impact in addressing biofilm-associated problems.

Newer antibiotics for the treatment of peritoneal dialysis-related peritonitis

Peritonitis is a debilitating infectious complication of peritoneal dialysis (PD). Drug-resistant bacterial peritonitis typically has a lower response rate to antibiotics. In the past 15 years, newer antibiotics with activities against drug-resistant Gram-positive bacteria have been developed. In most circumstances, peritonitis due to methicillin-resistant staphylococci responds to vancomycin. If vancomycin cannot be used due to allergy and/or non-susceptibility, there is increasing evidence that linezolid and daptomycin are the drugs of choice. It is reasonable to start linezolid orally or intravenously, but subsequent dose reduction may be necessary in case of myelosuppression. Daptomycin can be given intravenously or intraperitoneally and has excellent anti-biofilm activity. Other treatment options for drug-resistant Gram-positive bacterial peritonitis include teicoplanin, tigecycline and quinupristin/dalfopristin. Teicoplanin is not available in some countries (e.g. the USA). Tigecycline can only be given intravenously. Quinupristin/dalfopristin is ineffective against Enterococcus faecalis and there is only low-quality evidence to support its efficacy in the treatment of peritonitis. Effective newer antibiotics against drug-resistant Gram-negative bacteria are lacking. Polymyxins can be considered, but evidence on its efficacy is limited. In this review, we will discuss the potential use of newer antibiotics in the treatment of drug-resistant bacterial peritonitis in PD patients.

Exopolysaccharide biosynthetic glycoside hydrolases can be utilized to disrupt and prevent Pseudomonas aeruginosa biofilms

Bacterial biofilms present a significant medical challenge because they are recalcitrant to current therapeutic regimes. A key component of biofilm formation in the opportunistic human pathogen Pseudomonas aeruginosa is the biosynthesis of the exopolysaccharides Pel and Psl, which are involved in the formation and maintenance of the structural biofilm scaffold and protection against antimicrobials and host defenses. Given that the glycoside hydrolases PelAh and PslGh encoded in the pel and psl biosynthetic operons, respectively, are utilized for in vivo exopolysaccharide processing, we reasoned that these would provide specificity to target P. aeruginosa biofilms. Evaluating these enzymes as potential therapeutics, we demonstrate that these glycoside hydrolases selectively target and degrade the exopolysaccharide component of the biofilm matrix. PelAh and PslGh inhibit biofilm formation over a 24-hour period with a half maximal effective concentration (EC50) of 69.3 ± 1.2 and 4.1 ± 1.1 nM, respectively, and are capable of disrupting preexisting biofilms in 1 hour with EC50 of 35.7 ± 1.1 and 12.9 ± 1.1 nM, respectively. This treatment was effective against clinical and environmental P. aeruginosa isolates and reduced biofilm biomass by 58 to 94%. These noncytotoxic enzymes potentiated antibiotics because the addition of either enzyme to a sublethal concentration of colistin reduced viable bacterial counts by 2.5 orders of magnitude when used either prophylactically or on established 24-hour biofilms. In addition, PelAh was able to increase neutrophil killing by ~50%. This work illustrates the feasibility and benefits of using bacterial exopolysaccharide biosynthetic glycoside hydrolases to develop novel antibiofilm therapeutics.

Effects of vancomycin, daptomycin, and tigecycline on coagulase-negative staphylococcus biofilm and bacterial viability within biofilm: an in vitro biofilm model

Bacteria may hide in a hydrated polysaccharide matrix known as a biofilm. The structure of the bacterial biofilm renders phagocytosis difficult and increases antibiotic resistance. We hypothesized that repeated doses of antibiotics have an effect on bacteria within the biofilm and that it could inhibit or eradicate biofilm formation. Two clinical biofilm-positive coagulase-negative staphylococcus isolates were evaluated. The effects of antibiotics on preformed and nascent biofilm and on bacterial eradication within the biofilm were determined using different doses of vancomycin, daptomycin, and tigecycline for different durations in an in vitro biofilm model. Vancomycin neither penetrated the biofilm nor had any microbicidal effect on bacteria within the biofilm. Daptomycin had a microbicidal effect on bacteria within the biofilm but had no effect on biofilm inhibition and eradication (independent from dose and treatment time). Tigecycline inhibited and eradicated biofilm formation and had a microbicidal effect on bacteria within the biofilm. In conclusion, (i) biofilm formation appeared to be a major barrier to vancomycin activity, (ii) daptomycin had an antimicrobial effect on the bacteria within the biofilm but not on the biofilm burden, and (iii) tigecycline had effects both on bacteria within the biofilm and on biofilm burden. Thus, both tigecycline and daptomycin might be promising candidates for the treatment of biofilm infections.

Assessment of the Antimicrobial Activity of Algae Extracts on Bacteria Responsible of External Otitis

External otitis is a diffuse inflammation around the external auditory canal and auricle, which is often occurred by microbial infection. This disease is generally treated using antibiotics, but the frequent occurrence of antibiotic resistance requires the development of new antibiotic agents. In this context, unexplored bioactive natural candidates could be a chance for the production of targeted drugs provided with antimicrobial activity. In this paper, microbial pathogens were isolated from patients with external otitis using ear swabs for over one year, and the antimicrobial activity of the two methanol extracts from selected marine (Dunaliella salina) and freshwater (Pseudokirchneriella subcapitata) microalgae was tested on the isolated pathogens. Totally, 114 bacterial and 11 fungal strains were isolated, of which Staphylococcus spp. (28.8%) and Pseudomonas aeruginosa (P. aeruginosa) (24.8%) were the major pathogens. Only three Staphylococcus aureus (S. aureus) strains and 11 coagulase-negative Staphylococci showed resistance to methicillin. The two algal extracts showed interesting antimicrobial properties, which mostly inhibited the growth of isolated S. aureus, P. aeruginosa, Escherichia coli, and Klebsiella spp. with MICs range of 1.4 × 10⁹ to 2.2 × 10¹⁰ cells/mL. These results suggest that the two algae have potential as resources for the development of antimicrobial agents.

Evaluation of Ceftaroline Alone and in Combination against Biofilm-Producing Methicillin-Resistant Staphylococcus aureus with Reduced Susceptibility to Daptomycin and Vancomycin in an In Vitro Pharmacokinetic/Pharmacodynamic Model

Annually, medical device infections are associated with >250,000 catheter-associated bloodstream infections (CLABSI), with up to 25% mortality. Staphylococcus aureus, a primary pathogen in these infections, is capable of biofilm production, allowing organism persistence in harsh environments, offering antimicrobial protection. With increases in S. aureus isolates with reduced susceptibility to current agents, ceftaroline (CPT) offers a therapeutic alternative. Therefore, we evaluated whether CPT would have a role against biofilm-producing methicillin-resistant S. aureus (MRSA), including those with decreased susceptibilities to alternative agents. In this study, we investigated CPT activity alone or combined with daptomycin (DAP) or rifampin (RIF) against 3 clinical biofilm-producing MRSA strains in an in vitro biofilm pharmacokinetic/pharmacodynamic (PK/PD) model. Simulated antimicrobial regimens were as follows: 600 mg of CPT every 8 h (q8h) (free maximum concentration of drug [fCmax], 17.04 mg/liter; elimination half-life [t1/2], 2.66 h), 12 mg/kg of body weight/day of DAP (fCmax, 14.7 mg/liter; t1/2, 8 h), and 450 mg of RIF q12h (fCmax, 3.5 mg/liter; t1/2, 3.4 h), CPT plus DAP, and CPT plus RIF. Samples were obtained and plated to determine colony counts. Differences in log10 CFU/cm(2) were evaluated by analysis of variance with Tukey's post hoc test. The strains were CPT and vancomycin susceptible and DAP nonsusceptible (DNS). CPT displayed activity throughout the experiment. DAP demonstrated initial activity with regrowth at 24 h in all strains. RIF was comparable to the drug-free control, and little benefit was observed when combined with CPT. CPT plus DAP displayed potent activity, with an average log10 CFU/cm(2) reduction of 3.33 ± 1.01 from baseline. CPT demonstrated activity against biofilm-producing DNS MRSA. CPT plus DAP displayed therapeutic enhancement over monotherapy, providing a potential option for difficult-to-treat medical device infections.

Antimicrobial activity of synthetic cationic peptides and lipopeptides derived from human lactoferricin against Pseudomonas aeruginosa planktonic cultures and biofilms

Background

Infections by Pseudomonas aeruginosa constitute a serious health threat because this pathogen –particularly when it forms biofilms – can acquire resistance to the majority of conventional antibiotics. This study evaluated the antimicrobial activity of synthetic peptides based on LF11, an 11-mer peptide derived from human lactoferricin against P. aeruginosa planktonic and biofilm-forming cells. We included in this analysis selected N-acylated derivatives of the peptides to analyze the effect of acylation in antimicrobial activity. To assess the efficacy of compounds against planktonic bacteria, microdilution assays to determine the minimal inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time-kill studies were conducted. The anti-biofilm activity of the agents was assessed on biofilms grown under static (on microplates) and dynamic (in a CDC-reactor) flow regimes.

Results

The antimicrobial activity of lipopeptides differed from that of non-acylated peptides in their killing mechanisms on planktonic and biofilm-forming cells. Thus, acylation enhanced the bactericidal activity of the parental peptides and resulted in lipopeptides that were uniformly bactericidal at their MIC. In contrast, acylation of the most potent anti-biofilm peptides resulted in compounds with lower anti-biofilm activity. Both peptides and lipopeptides displayed very rapid killing kinetics and all of them required less than 21 min to reduce 1,000 times the viability of planktonic cells when tested at 2 times their MBC. The peptides, LF11-215 (FWRIRIRR) and LF11-227 (FWRRFWRR), displayed the most potent anti-biofilm activity causing a 10,000 fold reduction in cell viability after 1 h of treatment at 10 times their MIC. At that concentration, these two compounds exhibited low citotoxicity on human cells. In addition to its bactericidal activity, LF11-227 removed more that 50 % of the biofilm mass in independent assays. Peptide LF11-215 and two of the shortest and least hydrophobic lipopeptides, DI-MB-LF11-322 (2,2-dimethylbutanoyl-PFWRIRIRR) and DI-MB-LF11-215, penetrated deep into the biofilm structure and homogenously killed biofilm-forming bacteria.

Conclusion

We identified peptides derived from human lactoferricin with potent antimicrobial activity against P. aeruginosa growing either in planktonic or in biofilm mode. Although further structure-activity relationship analyses are necessary to optimize the anti-biofilm activity of these compounds, the results indicate that lactoferricin derived peptides are promising anti-biofilm agents.

Dynamics of biofilm formation and the interaction between Candida albicans and methicillin-susceptible (MSSA) and -resistant Staphylococcus aureus (MRSA)

Polymicrobial biofilms are an understudied and a clinically relevant problem. This study evaluates the interaction between C. albicans, and methicillin- susceptible (MSSA) and resistant (MRSA) S. aureus growing in single- and dual-species biofilms. Single and dual species adhesion (90 min) and biofilms (12, 24, and 48 h) were evaluated by complementary methods: counting colony-forming units (CFU mL-1), XTT-reduction, and crystal violet staining (CV). The secretion of hydrolytic enzymes by the 48 h biofilms was also evaluated using fluorimetric kits. Scanning electron microscopy (SEM) was used to assess biofilm structure. The results from quantification assays were compared using two-way ANOVAs with Tukey post-hoc tests, while data from enzymatic activities were analyzed by one-way Welch-ANOVA followed by Games-Howell post hoc test (α = 0.05). C. albicans, MSSA and MRSA were able to adhere and to form biofilm in both single or mixed cultures. In general, all microorganisms in both growth conditions showed a gradual increase in the number of cells and metabolic activity over time, reaching peak values between 12 h and 48 h (ρ<0.05). C. albicans single- and dual-biofilms had significantly higher total biomass values (ρ<0.05) than single biofilms of bacteria. Except for single MRSA biofilms, all microorganisms in both growth conditions secreted proteinase and phospholipase-C. SEM images revealed extensive adherence of bacteria to hyphal elements of C. albicans. C. albicans, MSSA, and MRSA can co-exist in biofilms without antagonism and in an apparent synergistic effect, with bacteria cells preferentially associated to C. albicans hyphal forms.

Phenotypic and genotypic characterization of Staphylococci causing breast peri-implant infections in oncologic patients

Background

Staphylococcus epidermidis and S. aureus have been identified as the most common bacteria responsible for sub-clinical and overt breast implant infections and their ability to form biofilm on the implant as been reported as the essential factor in the development of this type of infections. Biofilm formation is a complex process with the participation of several distinct molecules, whose relative importance in different clinical settings has not yet been fully elucidated. To our knowledge this is the first study aimed at characterizing isolates causing breast peri-implant infections.

Results

Thirteen S. aureus and seven S. epidermidis causing breast peri-implant infections were studied.

Using the broth microdilution method and the E-test, the majority of the strains were susceptible to all antibiotics tested. Methicillin resistance was detected in two S. epidermidis. All strains had different RAPD profiles and were able to produce biofilms in microtitre plate assays but, while all S. aureus carried and were able to express icaA and icaD genes, this was only true for one S. epidermidis. Biofilm development was glucose- and NaCl-induced (5 S. aureus and 1 S. epidermidis) or glucose-induced (the remaining strains). Proteinase K and sodium metaperiodate treatment had different effects on biofilms dispersion revealing that the strains studied were able to produce chemically different types of extracellular matrix mediating biofilm formation.

All S. aureus strains harboured and expressed the atlA, clfA, FnA, eno and cna genes and the majority also carried and expressed the sasG (10/13), ebpS (10/13) genes.

All S. epidermidis strains harboured and expressed the atlE, aae, embp genes, and the majority (six strains) also carried and expressed the fbe, aap genes.

Genes for S. aureus capsular types 5 and 8 were almost equally distributed. The only leukotoxin genes detected were lukE/lukD (6/13).

Conclusions

S. aureus and S. epidermidis breast peri-implant infections are caused by heterogeneous strains with different biofilm development mechanisms.

Since the collagen adhesin (cna) gene is not ubiquitously distributed among S. aureus, this protein could have an important role in the cause of breast peri-implant infections.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-015-0368-x) contains supplementary material, which is available to authorized users.

Evaluation of High-Dose Daptomycin Versus Vancomycin Alone or Combined with Clarithromycin or Rifampin Against Staphylococcus aureus and S. epidermidis in a Novel In Vitro PK/PD Model of Bacterial Biofilm

INTRODUCTION

Medical device infections are associated with significant morbidity and mortality. These difficult-to-treat infections often result in antibiotic failure and resistance. Combination therapy is often required, however, the most optimal combination is unknown. We evaluated the in vitro activity of daptomycin (DAP) or vancomycin (VAN) alone and in combination with rifampin (RIF) or clarithromycin (CLA) against strains of Staphylococcus aureus and S. epidermidis grown in biofilm on 3 prosthetic device materials.

METHODS

One methicillin-resistant S. aureus (MRSA R5266), one heteroresistant vancomycin-intermediate S. aureus (hVISA R3640), and one methicillin-resistant S. epidermidis (MRSE R461) strain was evaluated in a CDC biofilm reactor with titanium, Teflon®, and steel coupons. Regimens simulated included DAP 10 mg/kg/day, and VAN 1 g q12h alone or in combination with RIF 600 mg q24h or CLA 250 mg q12h. Additional regimens including DAP 12 mg/kg/day or VAN ± RIF 450 mg q12h were evaluated against the hVISA strain.

RESULTS

DAP + RIF or VAN + RIF demonstrated enhanced activity against R3640 in embedded biofilm (EB) cells in all materials versus DAP or VAN alone (P ≤ 0.040). Only DAP + RIF demonstrated sustained bactericidal activity (≥3.80 log10 CFU/cm2 reduction from baseline) against EB and planktonic cells of R5266 and EB cells of R461 in all 3 materials. Of interest, CLA did not appear to enhance DAP or VAN killing activities, and the addition of RIF prevented the emergence of resistance to DAP or VAN in all organisms.

CONCLUSION

Using an in vitro bacterial biofilm model containing three common prosthetic device materials, DAP + RIF and VAN + RIF were the most effective regimens. DAP + RIF displayed the greatest activity and represents a promising combination to evaluate for treatment of biofilm-associated staphylococcal infections.

A combined pharmacodynamic quantitative and qualitative model reveals the potent activity of daptomycin and delafloxacin against Staphylococcus aureus biofilms

Biofilms are associated with persistence of Staphylococcus aureus infections and therapeutic failures. Our aim was to set up a pharmacodynamic model comparing antibiotic activities against biofilms and examining in parallel their effects on viability and biofilm mass. Biofilms of S. aureus ATCC 25923 (methicillin-sensitive S. aureus [MSSA]) or ATCC 33591 (methicillin-resistant S. aureus [MRSA]) were obtained by culture in 96-well plates for 6 h/24 h. Antibiotic activities were assessed after 24/48 h of exposure to concentrations ranging from 0.5 to 512 times the MIC. Biofilm mass and bacterial viability were quantified using crystal violet and the redox indicator resazurin. Biofilms stained with Live/Dead probes were observed by using confocal microscopy. Concentration-effect curves fitted sigmoidal regressions, with a 50% reduction toward both matrix and viability obtained at sub-MIC or low multiples of MICs against young biofilms for all antibiotics tested. Against mature biofilms, maximal efficacies and potencies were reduced, with none of the antibiotics being able to completely destroy the matrix. Delafloxacin and daptomycin were the most potent, reducing viability by more than 50% at clinically achievable concentrations against both strains, as well as reducing biofilm depth, as observed in confocal microscopy. Rifampin, tigecycline, and moxifloxacin were effective against mature MRSA biofilms, while oxacillin demonstrated activity against MSSA. Fusidic acid, vancomycin, and linezolid were less potent overall. Antibiotic activity depends on biofilm maturity and bacterial strain. The pharmacodynamic model developed allows ranking of antibiotics with respect to efficacy and potency at clinically achievable concentrations and highlights the potential utility of daptomycin and delafloxacin for the treatment of biofilm-related infections.

Preparation and characterization of flexible nanoliposomes loaded with daptomycin, a novel antibiotic, for topical skin therapy

The purpose of this study was to investigate flexible nanoliposomes for mediating topical delivery of daptomycin, and to document permeation rates and bacteriostatic activity towards skin infections. Response surface methodology was used to optimize the daptomycin-loaded flexible nanoliposomes (DAP-FL), and the amount of drug loaded into the particles was evaluated as the investigation index. The optimal lipid ratio was lecithin to sodium cholate 17:1 (w/w) and the lipid to drug ratio was 14:1 (w/w). The hydration temperature was set at 37°C and the duration of treatment with ultrasound was 20 minutes. The DAP-FL obtained had a small mean particle size (55.4 nm) with a narrow size distribution (polydispersity index 0.15). The mean entrapment efficiency was 87.85% ± 2.15% and the mean percent drug loading was 5.61% ± 0.14%. Using skin mounted between the donor and receptor compartments of a modified Franz diffusion cell, the percentage and quantity of cumulative daptomycin permeation from DAP-FL within 12 hours were measured at 96.28% ± 0.70% and (132.23 ± 17.73) μg/cm(2) *5 = 661.15 ± 88.65 μg/cm(2), directly, showing rapid and efficient antibacterial activity against Staphylococcus aureus. Following local administration of DAP-FL, daptomycin was detected in multilayer tissues within the skin and underlying structures in the dorsal skin of the mouse. Effective therapeutic concentrations were maintained for several hours, and significantly inhibited bacterial growth and injury-induced biofilms. These results demonstrate that the DAP-FL can enhance the ability of daptomycin to permeate the skin efficiently, where it has a powerful antibacterial action and activity against biofilms. This novel formulation of daptomycin has potential as a new approach in the clinical application of daptomycin.

Daptomycin: local application in implant-associated infection and complicated osteomyelitis

BACKGROUND

The rise of highly resistant bacteria creates a persistent urge to develop new antimicrobial agents. This paper investigates the application of the lipopeptide antibiotic daptomycin in infections involving the human bone.

METHODS

Compressive and tensile strength testing of daptomycin-laden PMMA was performed referring to the ISO 5833. The microstructure of the antibiotic-laden PMMA was evaluated by scanning electron microscopy. Intracellular activity of daptomycin was determined by a human osteoblast infection model. Elution kinetics of the antibiotic-laden bone cement was measured by using a continuous flow chamber setup.

RESULTS

There was no significant negative effect of adding 1.225% and 7.5% per weight of daptomycin to the PMMA. There was no significant difference in intracellular activity comparing gentamicin to daptomycin. Elution of daptomycin from PMMA showed within the first-hour initial peak values of 15-20 μg/mL.

CONCLUSION

Daptomycin has a certain degree of activity in the intracellular environment of osteoblasts. Daptomycin admixed to PMMA remains bactericidal and does not significantly impair structural characteristics of the PMMA. The results of this paper suggest that daptomycin might be a potent alternative for treating osteomyelitis and implant-associated infection in trauma and orthopedic surgery caused by multiresistant strains.

The role of antimicrobial peptides in preventing multidrug-resistant bacterial infections and biofilm formation

Over the last decade, decreasing effectiveness of conventional antimicrobial-drugs has caused serious problems due to the rapid emergence of multidrug-resistant pathogens. Furthermore, biofilms, which are microbial communities that cause serious chronic infections and dental plaque, form environments that enhance antimicrobial resistance. As a result, there is a continuous search to overcome or control such problems, which has resulted in antimicrobial peptides being considered as an alternative to conventional drugs. Antimicrobial peptides are ancient host defense effector molecules in living organisms. These peptides have been identified in diverse organisms and synthetically developed by using peptidomimic techniques. This review was conducted to demonstrate the mode of action by which antimicrobial peptides combat multidrug-resistant bacteria and prevent biofilm formation and to introduce clinical uses of these compounds for chronic disease, medical devices, and oral health. In addition, combinations of antimicrobial peptides and conventional drugs were considered due to their synergetic effects and low cost for therapeutic treatment.

A dynamic in vitro model for evaluating antimicrobial activity against bacterial biofilms using a new device and clinical-used catheters

The activity of daptomycin compared to vancomycin against Staphylococcus epidermidis-biofilms on intravascular catheters has been evaluated using the new Sevilla device that enables to use medical grade-catheters, in an in vitro model that simulates the in vivo conditions. S. epidermidis-biofilms were obtained on polyurethane catheter segments using the Sevilla device linked to a continuous culture system for 24 h. To assess the antimicrobial activity, at this time the continuous culture system was changed to therapeutic antimicrobial concentration solutions for 48 h. At each 24 h interval time, catheter segments were taken out, washed and sonicated. Viable adherent bacteria were determined by agar plating. Data of surviving bacteria numbers attached to the catheter surface obtained with the Sevilla device showed a very good reproducibility. Daptomycin showed a good activity against S. epidermidis-biofilm on polyurethane catheter surface. After 48 h exposure to daptomycin, surviving adherent bacteria were reduced by 4 log compared to the control with no antimicrobial. Using the same model, vancomycin reduced bacterial survival by only 1.3 log. The Sevilla device enables antimicrobial agent activity against bacterial biofilms grown on the external surface of catheters used in clinical practice to be evaluated. The model used replicates as closely as possible the biofilm formed in a highly standardized way. Using this model, daptomycin demonstrates potent in vitro activity against S. epidermidis-biofilm on a polyurethane catheter; this activity was greater than that showed by vancomycin.

Efficacy of daptomycin combined with rifampicin for the treatment of experimental meticillin-resistant Staphylococcus aureus (MRSA) acute osteomyelitis

Daptomycin exhibits rapid bactericidal activity against Gram-positive organisms, including meticillin-resistant Staphylococcus aureus (MRSA). Daptomycin in combination with rifampicin needs to be assessed in bone infection. An MRSA acute osteomyelitis model was used. Daptomycin and vancomycin were compared, alone or in combination with rifampicin, over 4 days. Surviving bacteria were counted in bone, bone marrow and joint fluid. Vancomycin and daptomycin as single therapies were ineffective, but both combinations were significantly more effective than the corresponding monotherapy. Combination of daptomycin and rifampicin could prevent S. aureus from developing resistance. This combination could be a useful alternative to treat MRSA osteomyelitis at an early stage.

Activities of high-dose daptomycin, vancomycin, and moxifloxacin alone or in combination with clarithromycin or rifampin in a novel in vitro model of Staphylococcus aureus biofilm

Biofilm formation is an important virulence factor that allows bacteria to resist host responses and antibacterial agents. The aim of the study was to assess the in vitro activities of several antimicrobials alone or in combination against two Staphylococcus aureus isolates in a novel pharmacokinetic/pharmacodynamic (PK/PD) model of biofilm for 3 days. One methicillin-susceptible S. aureus strain (SH1000) and one methicillin-resistant S. aureus strain (N315) were evaluated in a modified biofilm reactor with polystyrene coupons. Simulated regimens included vancomycin (VAN) plus rifampin (RIF), moxifloxacin (MOX), and high doses (10 mg/kg of body weight/day) of daptomycin (DAP) alone or combined with RIF or clarithromycin (CLA). Against viable planktonic bacteria (PB) and biofilm-embedded bacteria (BB) of SH1000, neither DAP nor MOX alone was bactericidal. In contrast, the combination of DAP or MOX with CLA significantly increased the activity of the two agents against both PB and BB (P < 0.01), and DAP plus CLA reached the limit of detection at 72 h. Against PB of N315, DAP alone briefly achieved bactericidal activity at 24 h, whereas sustained bactericidal activity was observed at 32 h with VAN plus RIF. Overall, only a minimal reduction was observed with both regimens against BB (<2.8 log(10) CFU/ml). Finally, the combination of DAP and RIF was bactericidal against both PB and BB, achieving the limit of detection at 72 h. In conclusion, we developed a novel in vitro PK/PD model to assess the activities of antimicrobials against mature bacterial biofilm. Combinations of DAP or MOX with CLA were the most effective regimens and may represent promising options to treat persistent infections caused by S. aureus biofilms.

A simplified three-times weekly daptomycin dosing regimen for chronic hemodialysis patients

Approximately 2.3 million patients worldwide are undergoing chronic renal replacement therapy. In that population, acute infections substantially contribute to the excessive morbidity and mortality. The risk for invasive methicillin-resistant Staphylococcus aureus infections in this population is approximately 100-fold higher than in the general population, therefore dialysis patients currently account for up to approximately 15% of all invasive methicillin-resistant Staphylococcus aureus infections. A simplified three-times weekly dosing regimen for hemodialysis patients now allows for practical, hassle-free and effective treatment with daptomycin, which is licensed for the treatment of complicated skin and soft tissue infections, including resistant strains of Staphylococcus aureus and life-threatening Gram-positive infections, vancomycin-resistant enterococcal infections and right-sided endocarditis.

Activities of daptomycin and vancomycin alone and in combination with rifampin and gentamicin against biofilm-forming methicillin-resistant Staphylococcus aureus isolates in an experimental model of endocarditis

The findings of clinical and in vitro research support the theory that infective endocarditis (IE)-causing bacteria form biofilms and that biofilms negatively affect treatment outcomes. The purpose of the present study was to quantify the biofilm formation of methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) isolates obtained from patients with IE and to evaluate the in vitro activities of daptomycin and vancomycin alone and in combination with rifampin (rifampicin) or gentamicin while monitoring the isolates for the development of resistance. A high-inoculum, stationary-phase infection model of IE was used to simulate the pharmacokinetics in humans of daptomycin at 6 mg/kg of body weight/day, vancomycin at 1.25 g every 12 h (q12h) alone and in combination with rifampin at 300 mg every 8 h, and gentamicin at 1.3 mg/kg q12h. Two randomly selected clinical MRSA isolates were obtained from patients with IE; both MRSA isolates quantitatively produced biofilms. The time to bactericidal activity in the presence of daptomycin was isolate dependent but was achieved by 24 h for both MRSA isolates. Vancomycin did not achieve bactericidal activity throughout the experiment. At 24, 48, and 72 h, daptomycin-containing regimens had significantly more activity (greater declines in the mean number of CFU/g) than any of the vancomycin-containing regimens (P = 0.03). Rifampin and gentamicin antagonized or delayed the bactericidal activity of daptomycin (against MRSA B346846 for rifampin and against both isolates for gentamicin) in the first 24 h. Increases in the daptomycin and vancomycin MICs were not observed. We conclude that in an IE model of biofilm-forming MRSA, daptomycin monotherapy has better in vitro activity than daptomycin in combination with rifampin or gentamicin or any vancomycin-containing regimen studied within the first 24 h. Further investigations are needed to understand the initial delay in bactericidal activity observed when gentamicin or rifampin is combined with daptomycin.

Propionibacterium skull osteomyelitis treated with daptomycin

Propionibacterium acnes (P. acnes) is emerging as a pathogen in postneurosurgical infections. A case of cranial bone flap infection due to P. acnes successfully treated with daptomycin is presented. This case demonstrates the potential of daptomycin as an option in the treatment of P. acnes.

Pre-clinical experience with daptomycin

Daptomycin is a broad-spectrum, bactericidal agent active against Gram-positive bacteria, acting largely and unusually through membrane depolarization. Activity is markedly affected in vitro by the availability of calcium ions, and its high molecular weight with associated poor diffusion means that conventional disc diffusion testing is not reliable (and as a consequence not available). In order to allow susceptibility categorization, it is recommended that the MIC be determined in the presence of a defined calcium concentration. The activity of daptomycin is concentration-dependent with a prolonged post-antibiotic effect. It has linear pharmacokinetics, with a half-life of 8-9 h, the primary route of excretion is renal, it exhibits serum protein binding of approximately 92% and there is no interaction with the P450 cytochrome. Daptomycin is inactivated by surfactant in the lung and, in consequence, is not recommended for the treatment of respiratory infections. Daptomycin is currently licensed for the treatment of complicated skin and soft tissue infections and for bacteraemia and right-sided endocarditis due to methicillin-susceptible and -resistant Staphylococcus aureus. To date, daptomycin-resistant bacteria have rarely been isolated from patients, although increases in vancomycin MIC may be linked to reduced susceptibility to daptomycin. Close monitoring of resistance is essential to maintain the clinical utility of the drug. Using once-daily dosing, daptomycin has been generally well tolerated; however, weekly monitoring of creatinine phosphokinase is recommended, as myopathy in skeletal muscles has been seen, albeit rarely. The rapid bactericidal action of daptomycin makes it a useful addition to the therapeutic armamentarium for the treatment of Gram-positive infections, providing a valuable alternative to vancomycin when it is inappropriate or resistance is a problem.

Daptomycin in endocarditis and bacteraemia: a British perspective

Assessment of the place of daptomycin in the treatment of endocarditis and bacteraemia requires assimilation of data from one open-label randomized comparative clinical trial sized for equivalence, from registry data and from case reports. Selected relevant animal models and in vitro data are also considered in an effort to produce an integrated assessment of the current place of daptomycin in treatment. The evidence for the use of daptomycin is best in Staphylococcus aureus bacteraemia and endocarditis, but also includes some data on infections due to Enterococcus spp., especially if vancomycin-resistant. The emergence of resistance in a minority of patients on current dose regimens may mean that trials have to be repeated with higher doses, or the drug used in a combined therapy where rifampicin may be the best choice. In general, equivalence to comparator antibiotic regimens and a correlation for in vitro and in vivo findings have been demonstrated, but there are important gaps in the clinical data including a comparative equivalence trial in streptococcal and enterococcal endocarditis. Clinical benefit might be anticipated, but has not been proved, over aminoglycoside-containing regimens, and economic assessments are critical in the decision as to when and how daptomycin is deployed.

Current and novel antibiotics against resistant Gram-positive bacteria

The challenge posed by resistance among Gram-positive bacteria, epitomized by methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE) and vancomycin-intermediate and -resistant S. aureus (VISA and VRSA) is being met by a new generation of antimicrobials. This review focuses on the new β-lactams with activity against MRSA (ceftobiprole and ceftaroline) and on the new glycopeptides (oritavancin, dalbavancin, and telavancin). It will also consider the role of vancomycin in an era of existing alternatives such as linezolid, daptomycin and tigecycline. Finally, compounds in early development are described, such as iclaprim, friulimicin, and retapamulin, among others.