Daptomycin in bone and joint infections: a review of the literature

Antibacterial and antioxidant activity of cinnamon essential oil-laden 45S5 bioactive glass/soy protein composite scaffolds for the treatment of bone infections and oxidative stress

This study aimed to fabricate cinnamon essential oil (CO)-laden 45S5 bioactive glass (BG)/soy protein (SP) scaffolds exhibiting antioxidant and antibacterial activity. In this regard, 45S5 BG-based scaffolds were produced by the foam replica method, and subsequently the scaffolds were coated with various concentrations of CO (2.5, 5 and 7 (v/v) %) incorporated SP solution. Scanning electron microscopy images revealed that the CO-laden SP effectively attached to the 45S5 BG scaffold struts. The presence of 45S5 BG, SP and CO was confirmed using Fourier transform infrared spectroscopy. Compressive strength results indicated that SP based coatings improved the scaffolds' mechanical properties compared to uncoated BG scaffolds. The loading efficiency and releasing behaviour of the different CO concentrations were tested by gas chromatography-mass spectroscopy and UV-Vis spectroscopy. The results showed that CO incorporated scaffolds have controlled releasing behaviour over seven days. Furthermore, the coating on the scaffold surfaces slightly retarded, but it did not inhibit, the in vitro bioactivity of the scaffolds. Moreover, the antioxidant and antibacterial activity of CO was studied. The free radical scavenging activity measured by DPPH was 5 ± 1, 41 ± 3, 44 ± 1 and 43 ± 1 % for BGSP, CO2.5, CO5 and CO7, respectively. The antioxidant activity was thus enhanced by incorporating CO. Agar diffusion and colony counting results indicated that the incorporation of CO increased the antibacterial activity of scaffolds against S. aureus and E. coli. In addition, cytotoxicity of the scaffolds was investigated using MG-63 osteoblast-like cells. The results showed that the BG-SP scaffold was non-toxic under the investigated conditions, whereas dose-dependent toxicity was observed in CO-laden scaffolds. Considered together, the developed phytotherapeutic agent laden 45S5 BG-based scaffolds are promising for bone tissue engineering exhibiting capability to combat bone infections and to protect against oxidative stress damage.

Elution Profiles of Synthetic CaSO4 Hemihydrate Beads Loaded with Vancomycin and Tobramycin

Backgrounds and Objectives

The use of local antibiotic delivery vehicles is common in the management of biofilm-related infections as they provide high concentrations of local antibiotics while simultaneously avoiding complications from systemic toxicity. We present a 100% pure synthetic calcium sulfate hemi-hydrate mixed with 240 mg tobramycin and 500 mg vancomycin per 10 cc mixture for use in revision surgeries of periprosthetic joint infections (PJIs). The purified carrier demonstrates bioabsorbablity, promotion of bone growth, a physiologically favorable pH, and hydrophilicity. These unique properties may alleviate persistent postoperative wound drainage seen in patients with PJI. Our questions consist of two parts: (1) does the novel calcium sulfate carrier provide therapeutic concentrations of antibiotic locally that can kill biofilm related infections? (2) Are serum concentrations of antibiotic significant to cause concern for systemic toxicity?

Methods

To address these questions, we assayed the elution of antibiotic concentrations obtained from surgical drains and serum among 50 patients in the first 5 postoperative days.

Results

The elution of vancomycin and tobramycin was greatest on day 1 compared with those concentrations obtained on days 2, 3, 4, and 5; serum concentrations were largely undetectable. Our findings demonstrate that this calcium sulfate preparation provides therapeutic delivery of vancomycin and tobramycin locally at log 2–3 above the minimum inhibitory concentration (MIC), while avoiding toxic serum concentrations.

Conclusions

When used in one-stage revision arthroplasties, the bioabsorbable, purified carrier delivers high concentrations of antibiotic while avoiding systemic toxicity.

Biomechanical comparison of tigecycline loaded bone cement with vancomycin and daptomycin loaded bone cements

OBJECTIVE

The objectives of this study were "1" to analyze the compressive and tensile mechanical strength characteristics of tigecycline loaded bone cement and "2" to compare them with those of vancomycin and daptomycin loaded bone cements which are used in prosthetic joint infections complicated with resistant microorganisms.

METHODS

In this study, three experimental groups, which consisted of vancomycin (subgroups containing 1 g, 2 g, and 3 g vancomycin), daptomycin (subgroups containing 0.5 g, 1 g, and 1.5 g daptomycin), and tigecycline (subgroups containing 50 mg, 100 mg, and 150 mg tigecycline) and one control group without antibiotics were used. Using a standardized protocol, all antibiotic loaded bone cements were prepared. For each antibiotic group, including the control group, 10 samples were tested. All samples were biomechanically tested in terms of compressive strength and tensile strength.

RESULTS

Compression tests showed that all determined antibiotic concentrations resulted in a significant decrease when compared with the control group (p<0.0011). Vancomycin and daptomycin study groups demonstrated lower tensile strength than the control group (p<0.0011). However, comparison of tensile values of tigecycline study groups with the control group revealed no significant difference (p>0.0011). In addition, all statistically significant results from between groups comparisons revealed higher tensile and compressive mechanical strength values for the tigecycline groups (p<0.0011).

CONCLUSION

Evidence from this study has demonstrated that tigecycline loaded bone cement may have no mechanical disadvantage compared with vancomycin and daptomycin loaded bone cements in terms of mechanical strength when used at defined concentrations.

Daptomycin-Tobramycin Cement Beads have Lethal Local Antibacterial Effect in Resistant Periprosthetic Joint Infections

Background Resistant periprosthetic joint infection (PJI) can be a devastating complication of surgery and is difficult to treat. We attempted to identify the utility of Daptomycin/Tobramycin-impregnated polymethylmethacrylate (PMMA) beads in resistant PJIs. Methods Charts of patients with hip or knee PJI at a single academic medical center, with surgeries performed from May 2008 through May 2018, were reviewed retrospectively. The diagnosis of PJI was consistent with the Musculoskeletal Infection Society recommendations. Prosthetic joints underwent radical anterior-posterior synovectomy and placement of antibiotic cement beads in the infected joint. Clinical cure rate and local intraarticular antibiotic concentration were measured. Results Forty-four patients experienced 53 episodes of PJI, requiring 88 surgeries. There was a fairly even split between hip and knee PJI. The cure rate was 92% (11/12) for patients who had any infection with methicillin-resistant staphylococci during the evaluation period, compared with 62% (13/21) for patients with methicillin-susceptible Staphylococci. On days one and seven, the addition of tobramycin increased daptomycin concentrations by 47% and 3374%, respectively, for beads made onsite compared to elution of daptomycin alone. Elution increased by 44% and 8394%, respectively, for commercial beads compared to beads fabricated onsite. Conclusions Daptomycin-Tobramycin-loaded PMMA beads are safe and powerful bactericidal agents in prosthetic joint infections.

Topical rifampin powder for orthopedic trauma part I: Rifampin powder reduces recalcitrant infection in a delayed treatment musculoskeletal trauma model

Open fractures become infected despite meticulous debridement and care. Locally applied antibiotics, commonly embedded in polymethylmethacrylate, deliver high doses of drug directly to the fracture site. Direct application of antibiotic powder, which is being applied prophylactically in spine surgery, is a recent interest in the trauma sector, where bacterial biofilms are more prevalent. Traditional antibiotics, such as vancomycin, are poor performers against bacterial biofilms thus are ineffective in delayed treatment. Rifampin is an effective eradicator of Staphylococcal biofilms. Here, a rat model of musculoskeletal trauma was used to evaluate the utility of locally applied rifampin powder for reducing established orthopedic Staphylococcal infections in a delayed treatment scenario that previously indicated the limited use of local vancomycin. By applying rifampin powder directly to the contaminated segmental defect, the number of bacteria, as well as clinical indications of infection, were significantly reduced compared to vancomycin and daptomycin. Considering the Infectious Disease Society of America's recommendation to use rifampin in combination with another antibiotic to reduce the onset of rifampin resistance, rifampin powder was also applied in combination with vancomycin or daptomycin with insignificant changes in eradication performance. No indications of rifampin resistance were identified. Clinical Significance: The use of locally applied rifampin is a promising therapy for mature and tolerant musculoskeletal infections. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. J Orthop Res 36:3136-3141, 2018.

Changes in Antibiotic Susceptibility of Staphylococcus aureus Between the Stages of 2-Stage Revision Arthroplasty

BACKGROUND

Staphylococcus aureus is the predominant cause of periprosthetic joint infection (PJI) and can persist at the time of planned second stage of 2-stage revision arthroplasty, despite antibiotic cement spacer insertion and parenteral antibiotic therapy. Given the rapid emergence of antibiotic resistance, it is important to determine whether the antibiotic susceptibility of microorganisms changes between the stages of a 2-stage revision.

METHODS

A total of 1614 2-stage revision hip/knee arthroplasties performed for PJI at 2 academic institutions from 2000 to 2015 were identified. S aureus (methicillin susceptible and/or resistant) was isolated by culture in 402 (24.9%) cases during the first stage (resection arthroplasty). S aureus persisted and was cultured in 30 cases (knees = 18, hips = 12) during the second stage. Minimum inhibitory concentrations (MICs), demographics, antibiotic therapy, and surgical history were collected. The MICs at the time of the first-stage and second-stage surgeries were compared.

RESULTS

Nine (30%) revisions had an increase in vancomycin MIC. Six had an increase from ≤0.5 to 1 μg/mL, 2 had an increase from ≤0.5 to 2 μg/mL, and 1 had an increase from 1 to 2 μg/mL. All of the 9 revisions with an increase in vancomycin MIC had vancomycin in spacer.

CONCLUSION

Increases in the MICs were observed for vancomycin, the antibiotic widely used in cement spacers, in about one-third of the revisions. Despite the small sample size, the data from this preliminary study raise concern about the potential for emergence of resistant organisms between the stages of a 2-stage revision.

Methicillin Resistant Staphylococcus Aureus Sacroiliac Joint Septic Arthritis in an Adult Patient Treated with Daptomycin

Sacroiliac joint septic arthritis is a rare disease entity representing 1-2% of all cases of septic arthritis. Establishment of the diagnosis is often challenging given the non-specific presenting features and the potential cross-over with other pathologies. We report the case of a 50 year old gentleman who suffers with psoriasis and presented with sacroiliac joint septic arthritis complicated by Methicillin Resistant Staphylococcus Aureus (MRSA) bacteraemia and an iliopsoas abscess. This was successfully treated conservatively with a course of the novel antibiotic Daptomycin.

Acute bacterial sternoclavicular osteomyelitis in a long-term renal transplant recipient

Kidney transplantation is the treatment of choice for a significant number of patients with end-stage renal disease. Although immunosuppression therapy improves graft and patient’s survival, it is a major risk factor for infection following kidney transplantation altering clinical manifestations of the infectious diseases and complicating both the diagnosis and management of renal transplant recipients (RTRs). Existing literature is very limited regarding osteomyelitis in RTRs. Sternoclavicular osteomyelitis is rare and has been mainly reported after contiguous spread of infection or direct traumatic seeding of the bacteria. We present an interesting case of acute, bacterial sternoclavicular osteomyelitis in a long-term RTR. Blood cultures were positive for Streptococcus mitis, while the portal entry site was not identified. Magnetic resonance imaging of the sternoclavicluar region and a three-phase bone scan were positive for sternoclavicular osteomyelitis. Eventually, the patient was successfully treated with Daptomycin as monotherapy. In the presence of immunosuppression, the transplant physician should always remain alert for opportunistic pathogens or unusual location of osteomyelitis.

Complete Genome Sequence of Enterococcus Bacteriophage EFLK1

We previously isolated EFDG1, a lytic phage against enterococci for therapeutic use. Nevertheless, EFDG1-resistant bacterial strains (EFDG1^r) have evolved. EFLK1, a new highly effective phage against EFDG1^r strains, was isolated in this study. The genome of EFLK1 was fully sequenced, analyzed, and deposited in GenBank.

Bacteremia with an iliopsoas abscess and osteomyelitis of the femoral head caused by Enterococcus avium in a patient with end-stage kidney disease

A 70-year-old man on hemodialysis for end-stage kidney disease due to polycystic kidney disease presented with hip pain on extension and a high C-reactive protein level. Further examinations revealed an iliopsoas abscess and femoral head osteomyelitis caused by Enterococcus avium (E. avium) detected in blood and pus cultures. Complete resolution of the infection with ampicillin-resistant E. avium required six months of vancomycin therapy and two surgical drainage procedures. There have been no previous case reports in which both blood and abscess cultures confirmed E. avium infection. Careful attention should be paid to the detection of non-specific symptoms in patients on hemodialysis, with blood cultures being essential in such cases.

Establishment of a new methicillin resistant Staphylococcus aureus animal model of osteomyelitis

PURPOSE

The increase in methicillin-resistant Staphylococcus aureus (MRSA) infections is currently a major health care problem. Vancomycin is still often the first-line anti-microbiological agent for treating such infections; however, a recent decline in efficacy of vancomycin in MRSA infections has raised concerns and accelerated the search for new antibiotics. The aim of this study was to establish a MRSA peri-implant osteomyelitis animal model for future testing of new anti-microbiological agents under typical MRSA infection conditions.

METHODS

Eighteen randomised NZW-rabbits underwent a standardised surgical procedure with the insertion of a femoral bone implant. Animals were then divided into group 1 (MRSA inoculation, no antibiotics; M/N), group 2 (MRSA inoculation, Vancomyin; M/V), and group 3 (no MRSA inoculation, no antibiotics; N/N). The primary study outcome parameters were animal leucocyte count, animal weight, and animal body temperature at one, seven, and 42 days after surgery. Additionally, a histo-morphometrical score was established and adjusted to a modified histological Smeltzer score.

RESULTS

Macroscopic and histo-morphometrical findings showed a peri-implant osteomyelitis in group 1 with both increased acute and chronic infection parameters in M/N, as compared to M/V and N/N, indicating that vancomycin treatment prevented typical morphological changes of MRSA peri-implant osteomyelitis. Similarly, there was a reduction in animal weight and increase in leucocyte count and body temperature in group 1 (each p < 0.005). Vancomycin treatment again resulted in significantly reduced leucocyte count and body temperature, and increased animal body weight.

CONCLUSIONS

Here we have established a peri-implant MRSA osteomyelitis model that successfully combined clinical and laboratory outcome parameters of infection with histo-morphometrical results; this model appears to be valuable for future experimental use and therapeutic monitoring of new anti-microbiological MRSA drugs.

Daptomycin-loaded polymethylmethacrylate bone cement for joint arthroplasty surgery

Antibiotic-loaded acrylic bone cement has been frequently used as an infection prophylaxis or antibiotic-loaded spacer in infected arthroplasty. In addition, daptomycin has been used recently against broad spectrum Gram-positive organisms. The goal of this in vitro study is to investigate the bacteriacidal and mechanical properties of daptomycin-incorporated polymethylmethacrylate (PMMA) bone cement and evaluate its feasibility for clinical use. Daptomycin (0.5, 1, or 2 g) was premixed with 40 g of PMMA bone cement powder before curing. The mechanical properties of the daptomycin-loaded acrylic bone cement (DLABC) were estimated following standard guidance, and the release profile and kinetics of daptomycin from PMMA were analyzed. The antimicrobial efficacy of DLABC was determined with a zone of inhibition (ZOI) assay against Staphylococcus aureus, Staphylococcus epidermis, Enterococcus faecalis, and Enterococcus faecium, respectively. The results showed that the compressive strength, of PMMA bone cement, which was higher than 100 MPa in all groups, was sufficient according to ISO 5833 after incorporation of daptomycin. The encapsulated daptomycin was released for 2 weeks with a 9.59 ± 0.85%, 15.25 ± 0.69%, and 20.64 ± 20.33% released percentage on the first day in the low, mid, and high groups, respectively. According to the calculated release kinetics, incorporated daptomycin should be 3.3 times the original dose to double its release. Although all recipes of DLABC had a microbial inhibitory effect, the effect with a higher encapsulated amount of daptomycin was more significant. Therefore, we believe that daptomycin can be locally delivered from PMMA bone cement at the surgical site as a prophylactic or treatment for osteomyelitis against Gram-positive organisms with intact cement function.

In vitro activity of daptomycin against Enterococcus faecalis under various conditions of growth-phases, inoculum and pH

Enterococcus faecalis (E. faecalis) has become a major leading cause of nosocomial endocarditis. Treatment of such infections remains problematic and new therapeutic options are needed. Nine E. faecalis strains were tested: six obtained from patients presenting endocarditis, one with isolated bacteremia, and two reference strains. Antibiotics included daptomycin, alone or in combination, linezolid, tigecycline, rifampicin, gentamicin, teicoplanin, ceftriaxone and amoxicillin. Time-kill studies included colony counts at 1, 4 and 24 h of incubation. Significant bactericidal activity was defined as a decrease of ≥3log₁₀CFU/ml after 24 h of incubation. Antibiotics were tested at a low (10⁶ CFU/ml) and high (10⁹ CFU/ml) inoculum, against exponential- and stationary-phase bacteria. We also performed time kill studies of chemically growth arrested E. faecalis. Various pH conditions were used during the tests. In exponential growth phase and with a low inoculum, daptomycin alone at 60 µg/ml and the combination amoxicillin-gentamicin both achieved a 4-log₁₀ reduction in one hour on all strains. In exponential growth phase with a high inoculum, daptomycin alone was bactericidal at a concentration of 120 µg/ml. All the combinations tested with this drug were indifferent. In stationary phase with a high inoculum daptomycin remained bactericidal but exhibited a pH dependent activity and slower kill rates. All combinations that did not include daptomycin were not bactericidal in conditions of high inoculum, whatever the growth phase. The results indicate that daptomycin is the only antibiotic that may be able of overcoming the effects of growth phase and high inoculum.

Randomized controlled trial of the safety and efficacy of Daptomycin versus standard-of-care therapy for management of patients with osteomyelitis associated with prosthetic devices undergoing two-stage revision arthroplasty

The prevalence of Staphylococcus aureus causing prosthetic joint infection (PJI) supports investigation of higher doses of daptomycin in the management of PJI. This was a prospective, randomized controlled trial studying safety and efficacy of daptomycin (6 and 8 mg/kg of body weight) compared with standard-of-care therapy for PJI. This open-label study randomized 75 patients undergoing 2-stage revision arthroplasty to daptomycin at 6 or 8 mg/kg or a comparator (vancomycin, teicoplanin, or semisynthetic penicillin). After prosthesis removal, patients received 6 weeks of antibiotic treatment and a 2- to 6-week antibiotic-free period before implantation of a new prosthesis. Test of cure (TOC) was within 1 to 2 weeks after reimplantation. The primary objective was evaluation of creatine phosphokinase (CPK) levels. Secondary objectives were clinical efficacy and microbiological assessments. Of 73 CPK safety population patients, CPK elevation of >500 U/liter occurred in 4 of 25 (16.0%) (daptomycin, 6 mg/kg) and 5 of 23 (21.7%) (daptomycin, 8 mg/kg) daptomycin-treated patients and 2 of 25 (8.0%) comparator patients. Adverse-event rates were similar among daptomycin and comparator groups. Among modified intent-to-treat patients at TOC, clinical success rates were 14 of 24 (58.3%) for 6 mg/kg daptomycin, 14 of 23 (60.9%) for 8 mg/kg daptomycin, and 8 of 21 (38.1%) for the comparator. Overall microbiological success at TOC was 12 of 24 (50.0%) for 6 mg/kg daptomycin, 12 of 23 (52.2%) for 8 mg/kg daptomycin, and 8 of 21 (38.1%) for comparator patients. In conclusion, daptomycin at 6 and 8 mg/kg given for up to 6 weeks was safe and appeared to be effective in managing staphylococcal PJI using a 2-stage revision arthroplasty technique in a total of 49 patients.

In vitro susceptibility of Staphylococcus aureus and Staphylococcus epidermidis isolated from prosthetic joint infections

Prosthetic joint infections (PJI) are severe complications in Orthopedics, with Staphylococcus aureus and Staphylococcus epidermidis being the most commonly isolated pathogens. The variable antimicrobial susceptibility found in these microorganisms, along with the increasing number of methicillin-resistant strains, increases the difficulty of antibiotic selection and makes it necessary to perform individual susceptibility studies to select the optimal antibiotic treatment. The aim of this study was to evaluate the in vitro susceptibility pattern of 35 clinical strains isolated from PJI (17 S. aureus and 18 S. epidermidis) against rifampin, vancomycin, tygecicline, clindamycin, cotrimoxazole, cloxacillin, ciprofloxacin, daptomycin and fosfomycin. In vitro susceptibility assays were performed using the broth microdilution method and agar dilution for fosfomycin. MBC was also determined. Tygecicline and daptomycin showed the highest antimicrobial activity with low MIC(90) values, and no resistant strains were detected. On the other hand, ciprofloxacin and cloxacillin exhibited a poor antimicrobial effect with a high percentage of nonsusceptible strains in both species. Bactericidal activity rates revealed the bacteriostatic behavior of rifampin, tygecicline, cotrimoxazole, fosfomycin and clindamycin, whereas vancomycin and cloxacillin showed species- and strain-dependent behavior. Daptomycin and ciprofloxacin were observed to be efficient bactericidal agents against the tested strains. According to our data, rifampin, tigecycline, daptomycin and fosfomycin showed high in vitro activity against most staphylococcal strains isolated from the PJIs tested, although daptomycin seems to be the best alternative to vancomycin therapy.

Antimicrobial options in the treatment of adult staphylococcal bone and joint infections in an era of drug shortages

Staphylococcus aureus is the most pathogenic bacterium and the most common cause of osteomyelitis, affecting 50% to 70% of cases. Many antistaphylococcal agents with varying activity against methicillin-susceptible S aureus and methicillin-resistant S aureus are available in the US market. This article reviews the most common antistaphylococcal agents used in the treatment of bone and joint infections in adult patients and focuses on the antimicrobial agent's mechanism of action, US Food and Drug Administration-approved indications, place in therapy, monitoring parameters, and common side effects.

Daptomycin resistance in prosthetic joint infections

Antimicrobial resistance has been problematic since the advent of antibiotics. Patients with prosthetic joint infections often require prolonged courses of antibiotic therapy, with resistance commonly being the consequence. The rapid evolution of resistance poses a serious challenge in the treatment of infections and creates a need for new agents with novel mechanisms of bactericidal activity. Daptomycin, a cyclic lipopeptide naturally produced by Streptomyces roseosporus, is a newer agent approved for use in complicated skin, soft tissue, and prosthetic joint infections. To our knowledge, this article describes the first case of daptomycin-resistant heterogenous vancomycin intermediate-resistant Staphylococcus aureus (hVISA) in an 82-year-old man undergoing elective total knee arthroplasty in Queensland, Australia, with a subsequent deep prosthetic joint infection.A literature review is presented, and the increasing number of multi-resistant organisms and their implications for orthopedics are discussed. Worldwide reports of hVISA are reviewed. To our knowledge, this is the first article to describe daptomycin resistance in prosthetic joint infections. The role of newer antimicrobial agents, such as daptomycin, and strategies to minimize antibiotic resistance are examined.

Characterization of daptomycin-loaded antibiotic cement

Antibiotics are commonly mixed with polymethylmethacrylate (PMMA) cement to suppress severe periprosthetic infections associated with total joint arthroplasty. The relationship between antibiotic concentration and the resulting elution kinetics remains unclear. The purpose of this study was to characterize the release of daptomycin from PMMA cement and the subsequent effects on mechanical properties.Varying concentrations of daptomycin and tobramycin were vacuum mixed in commercially available PMMA and subjected to an in vitro elution period. High-performance liquid chromatography was used to quantify the concentration of the amount of daptomycin eluted at predetermined time points. Samples were subjected to compressive loading to analyze the effect of antibiotic concentration on cement mechanical properties. Daptomycin elution increased when initial tobramycin concentration was increased. Furthermore, the addition of antibiotics increased the compressive strength of the cement in the postelution period. The binary addition of tobramycin with daptomycin antibiotics modifies the elution and mechanical properties of PMMA bone cement. Based on the findings of our study, 2 g of daptomycin and 3.6 g of tobramycin per 40-g packet of cement should be used to promote daptomycin elution without sacrificing PMMA mechanical properties.

Successful use of daptomycin in Panton-Valentine leucocidin positive Staphylococcus aureus paediatric osteomyelitis

INTRODUCTION

Efficacy of daptomycin has been recorded in adult Gram-positive bone and joint infections OAI (1) and daptomycin has been used as secondary or tertiary agent when primary agents have failed (1, 2) in the treatment of osteoarticular infections caused by Staphylococcus aureus.

PRESENTATION OF CASE

We report a 16-year-old schoolboy with Panton-Valentine Leucocidin (PVL) positive methicillin susceptible S. aureus osteomyelitis, who was refractory to 9days of recognised antimicrobial chemotherapy with progressive multifocal haematogenous spread. Subsequent addition of daptomycin promptly cleared the bacteraemia and arrested the disease process within 9days.

DISCUSSION

Although cases have been reported of daptomycin usage in children with invasive staphylococcus bacteraemia, endocarditis and OAI (2), we believe this to be the first case report describing the use of daptomycin in paediatric osteomyelitis caused by PVL positive S. aureus.

CONCLUSION

Repercussions of osteomyelitis, in particular those caused by PVL S. aureus, and evolving resistance patterns internationally, highlight the need for further evaluation of daptomycin in the paediatric arena. The response seen with the addition of Daptomycin in this case suggests possible reduction in hospital stay and number of surgical procedures when compared to other published series using conventional antibiotic regimens.

Successful salvage therapy with Daptomycin for osteomyelitis caused by methicillin-resistant Staphylococcus aureus in a renal transplant recipient with Fabry-Anderson disease

Daptomycin is licensed in adults for the management of Staphylococcus aureus methicillin-resistant infections, including bone and skin complicated infections. We describe for the first time its use in a renal transplant recipient for Fabry-Anderson Disease with right heel osteomyelitis. The patient was unresponsive to first-line Teicoplanin and second-line Tigecycline, whereas he was successfully treated with third-line Daptomycin monotherapy at 4 mg/Kg/qd for 4 weeks. Local debridement was performed in advance of each line of treatment.

Pharmacological agents for soft tissue and bone infected with MRSA: which agent and for how long?

Methicillin-resistant Staphylococcus aureus (MRSA) infections cause an important number of soft tissue and bone infections, although exact rates vary across different countries and institutions. The length of antibiotic treatment required depends upon the severity of infection and pre-existing co-morbidities. Monitoring response to treatment is important to ensure cure of infection whilst preventing excessive antibiotic use. Debridement and drainage, in addition to prosthesis removal, may be necessary. Numerous antibiotics are effective at treating soft tissue and bone infected with MRSA. Oral antibiotics, such as clindamycin, doxycycline and linezolid, generally offer good bioavailability and tissue penetration. They are separated largely by side effect profile and drug interactions, which should be considered carefully prior to use. There are also several agents only available in the intravenous (IV) form, for example glycopeptides, daptomycin and tigecycline. These are normally reserved for the treatment of severe infections. Whilst tissue penetration is variable within this group, it is the adverse events linked with each antibiotic that are most effective in determining the preferred agent.

Daptomycin, fosfomycin, or both for treatment of methicillin-resistant Staphylococcus aureus osteomyelitis in an experimental rat model

The in vivo activities of daptomycin, fosfomycin, and a combination of both antibiotics against a clinical isolate of methicillin-resistant Staphylococcus aureus (daptomycin MIC, 0.25 μg/ml; fosfomycin MIC, 0.5 μg/ml) were evaluated in a rat model of osteomyelitis. A total of 37 rats with experimental osteomyelitis were treated for 4 weeks with either 60 mg/kg of body weight of daptomycin subcutaneously once daily, 75 mg/kg fosfomycin intraperitoneally once daily, a combination of both drugs, or a saline placebo. After the completion of treatment, animals were euthanized, and the infected tibiae were processed for quantitative bacterial culture. Bone cultures were found to be positive for methicillin-resistant S. aureus in 9 of 9 (100%) animals of the placebo group, in 9 of 9 (100%) animals treated with daptomycin, in 1 of 10 (10%) fosfomycin-treated rats, and in 1 of 9 (22.2%) rats comprising the combination group. Results of bacterial counts in the bone samples were expressed as log(10) CFU/g of bone and analyzed by using the Mann-Whitney U test followed by Bonferroni's multiple-comparison test. Based on bacterial counts, treatment with daptomycin was significantly superior to placebo, although it remained inferior to treatment with fosfomycin. No synergistic or antagonistic effect was observed for the combination therapy. No development of resistance against daptomycin or fosfomycin was observed after the 4-week treatment period.

Two-stage revision surgery with preformed spacers and cementless implants for septic hip arthritis: a prospective, non-randomized cohort study

Background

Outcome data on two-stage revision surgery for deep infection after septic hip arthritis are limited and inconsistent. This study presents the medium-term results of a new, standardized two-stage arthroplasty with preformed hip spacers and cementless implants in a consecutive series of adult patients with septic arthritis of the hip treated according to a same protocol.

Methods

Nineteen patients (20 hips) were enrolled in this prospective, non-randomized cohort study between 2000 and 2008. The first stage comprised femoral head resection, debridement, and insertion of a preformed, commercially available, antibiotic-loaded cement hip spacer. After eradication of infection, a cementless total hip arthroplasty was implanted in the second stage. Patients were assessed for infection recurrence, pain (visual analog scale [VAS]) and hip joint function (Harris Hip score).

Results

The mean time between first diagnosis of infection and revision surgery was 5.8 ± 9.0 months; the average duration of follow up was 56.6 (range, 24 - 104) months; all 20 hips were successfully converted to prosthesis an average 22 ± 5.1 weeks after spacer implantation. Reinfection after total hip joint replacement occurred in 1 patient. The mean VAS pain score improved from 48 (range, 35 - 84) pre-operatively to 18 (range, 0 - 38) prior to spacer removal and to 8 (range, 0 - 15) at the last follow-up assessment after prosthesis implantation. The average Harris Hip score improved from 27.5 before surgery to 61.8 between the two stages to 92.3 at the final follow-up assessment.

Conclusions

Satisfactory outcomes can be obtained with two-stage revision hip arthroplasty using preformed spacers and cementless implants for prosthetic hip joint infections of various etiologies.

Comparison of the pharmacokinetic properties of vancomycin, linezolid, tigecyclin, and daptomycin

The rapid antibiotic resistance development has created a major demand for new antimicrobial agents that can combat resistant strains such as methicillin-resistant S. aureus (MRSA). Until a short time ago, the glycopeptide vancomycin was the only therapeutic choice in this situation. However, in recent years some newer agents with different mechanisms of actions have been added to the arsenal, and more are on the horizon. For a successful therapy it is of vital importance that these compounds are used judiciously and dosed appropriately. The present article reviews the pharmacokinetic properties of vancomycin, linezolid, tigecycline and daptomycin. The first major difference between these compounds is their oral bioavailability. Only linezolid can be administered orally, whereas vancomycin, daptomycin and tigecycline are limited to parenteral use. Once in the body, they show very different disposition. Daptomycin has a very small volume of distribution of 7L indicating very little tissue distribution whereas tigecycline has a very large volume of distribution of 350-500 L. Vancomycin and linezolid are in-between with volumes of distribution of approximately 30 and 50 L, close to total body water. However, studies have shown that linezolid shows better tissue penetration than vancomycin. Newer studies using microdialysis, a new technique that allows direct monitoring of unbound tissue levels, support this finding. As far as drug elimination, daptomycin and vancomycin are mainly eliminated into the urine and require dosing adjustments in renally impaired patients, whereas tigecycline is eliminated into the bile and linezolid is metabolized so that in renal patients no dosing adjustments are needed for these compounds. Although the elimination pathways are very different, the resulting half-lives of linezolid, vancomycin, and daptomycin are not greatly different and vary from 4-8 h. Tigecycline, however, has a much longer half-life of up to 1-2 days due to the slow redistribution from tissue binding sites.

Efficacy of usual and high doses of daptomycin in combination with rifampin versus alternative therapies in experimental foreign-body infection by methicillin-resistant Staphylococcus aureus

The treatment of prosthetic joint infections caused by methicillin-resistant Staphylococcus aureus (MRSA) continues to be a challenge for the clinician. The aim of this study was to evaluate the efficacies of daptomycin at usual and high doses (equivalent to 6 and 10 mg/kg of body weight/day, respectively, in humans) and in combination with rifampin and to compare the activities to those of conventional anti-MRSA therapies. We used MRSA strain HUSA 304, with the following MICs and minimal bactericidal concentrations (MBCs), respectively: daptomycin, 1 μg/ml and 4 μg/ml; vancomycin, 2 μg/ml and 4 μg/ml; linezolid, 2 μg/ml and >32 μg/ml; and rifampin, 0.03 μg/ml and 0.5 μg/ml. In time-kill curves, only daptomycin and its combinations with rifampin achieved a bactericidal effect in log and stationary phases. For in vivo studies, we used a rat foreign-body infection model. Therapy was administered for 7 days with daptomycin at 100 mg/kg/day and 45/mg/kg/day, vancomycin at 50 mg/kg/12 h, rifampin at 25 mg/kg/12 h, and linezolid at 35 mg/kg/12 h, and each antibiotic was also combined with rifampin. Among monotherapies, daptomycin at 100 mg/kg/day and rifampin performed better than vancomycin and linezolid. In combination with rifampin, both dosages of daptomycin were significantly better than all other combinations, but daptomycin at 100 mg/kg/day plus rifampin achieved better cure rates at day 11 (P < 0.05) than daptomycin at 45 mg/kg/day plus rifampin. Resistant strains were found in monotherapies with rifampin and daptomycin at 45 mg/kg/day. In conclusion, daptomycin at high doses was the most effective monotherapy and also improved the efficacy of the combination with rifampin against foreign-body infections by MRSA. Clinical studies should confirm whether this combination may be considered the first-line treatment for foreign-body infections by MRSA in humans.

Treatment of infections caused by antimicrobial-resistant gram-positive bacteria

An increasing proportion of Staphylococcus aureus infections are caused by methicillin-resistant S aureus. Treatment of infections caused by this organism is challenging, especially because therapy with vancomycin, the traditional antibiotic of choice for methicillin-resistant S aureus infections, is associated with an increasing frequency of treatment failure, and vancomycin insensitive and vancomycin-resistant strains have emerged. In addition, Enterococcus sp. isolated from human infections are increasingly resistant to multiple antimicrobial agents. Newer drugs available for treatment of resistant Gram-positive bacterial infections in the United States include linezolid, daptomycin, tigecycline and telavancin. The precise role for these newer agents is still evolving. Organisms resistant to each of these antimicrobials have emerged. New drugs in development include cephalosporins and carbapenems with MRSA activity.

Efficacy of high doses of daptomycin versus alternative therapies against experimental foreign-body infection by methicillin-resistant Staphylococcus aureus

Since the currently approved dose of daptomycin (6 mg/kg of body weight/day) has been associated with clinical failures and resistance development, higher doses for some difficult-to-treat infections are being proposed. We studied the efficacy of daptomycin at high doses (equivalent to 10 mg/kg/day in humans) and compared it to that of reference and alternative treatments in a model of foreign-body infection with methicillin (meticillin)-resistant Staphylococcus aureus. In vitro studies were conducted with bacteria in the log and stationary phases. For the in vivo model, therapy with daptomycin at 100 mg/kg/day, vancomycin at 50 mg/kg/12 h, rifampin (rifampicin) at 25 mg/kg/12 h, or linezolid at 35 mg/kg/12 h was administered for 7 days. Antibiotic efficacy was evaluated using either bacteria from tissue cage fluids or those attached to coverslips. We screened for the emergence of linezolid- and rifampin-resistant strains and analyzed the surviving population from the daptomycin-treated group. Only daptomycin was bactericidal in both the log- and stationary-phase studies. Daptomycin (decrease in the log number of CFU per milliliter of tissue cage fluid, 2.57) and rifampin (decrease, 2.6 log CFU/ml) were better (P < 0.05) than vancomycin (decrease, 1.1 log CFU/ml) and linezolid (decrease, 0.9 log CFU/ml) in the animal model. Rifampin-resistant strains appeared in 60% of cases, whereas no linezolid resistance emerged. No daptomycin-resistant subpopulations were detected at frequencies of 10(-7) or higher. In conclusion, daptomycin at high doses proved to be as effective as rifampin, and the two were the most active therapies for this experimental foreign-body infection. These high doses ensured a profile of safety from the development of resistance.