Impact of bacterial biofilm on the treatment of prosthetic joint infections

Difficult-to-treat pathogens significantly reduce infection resolution in periprosthetic joint infections

Periprosthetic joint infection (PJI) is a feared complication after arthroplasty. Our hypothesis was that PJI caused by difficult-to-treat (DTT) pathogens has a worse outcome compared with non-DTT PJI. Routine clinical data on 77 consecutive patients with confirmed PJI treated with 2-stage exchange arthroplasty were placed in DTT and non-DTT PJI groups and analyzed. The main outcome variable was that the patient was definitively free of infection after 2 years. We found definitive infection resolution in 31 patients in the DTT group (68.9%) and 28 patients (87.5%) in the non-DTT group (P < 0.05). The necessity for revision surgery until assumed resolution of infection was significantly more frequent in the DTT group with 4.72 ± 3.03 operations versus 2.41 ± 3.02 operations in the non-DTT group (P < 0.05). PJI caused by DTT bacteria is associated with significantly higher numbers of revision operations and significantly inferior definitive infection resolution.

Evaluation of the ability of linezolid and tedizolid to eradicate intraosteoblastic and biofilm-embedded Staphylococcus aureus in the bone and joint infection setting

OBJECTIVES

Prolonged use of linezolid for bone and joint infection (BJI) is limited by its long-term toxicity. The better safety profile of tedizolid, a recently developed oxazolidinone, could offer an alternative. However, its efficacy against biofilm-embedded and intracellular Staphylococcus aureus, the two main bacterial reservoirs associated with BJI chronicity, is unknown.

METHODS

Using three S. aureus strains (6850 and two clinical BJI isolates), linezolid and tedizolid were compared regarding their ability: (i) to target the S. aureus intracellular reservoir in an in vitro model of osteoblast infection, using three concentrations increasing from the bone concentration reached with standard therapeutic doses (Cbone = 2.5 × MIC; Cplasm = 10 × MIC; Cmax = 40 × MIC); (ii) to eradicate mature biofilm [minimal biofilm eradication concentration (MBEC)]; and (iii) to prevent biofilm formation [biofilm MIC (bMIC) and confocal microscopy].

RESULTS

Linezolid and tedizolid weakly reduced the intracellular inoculum of S. aureus in a strain-dependent manner despite the similar MICs for the tested strains, but improved cell viability even in the absence of an intracellular bactericidal effect. Conversely, linezolid and tedizolid were ineffective in eradicating mature biofilm formed in vitro, with MBEC >2000 and >675 mg/L, respectively. bMICs of tedizolid were 4-fold lower than those of linezolid for all strains.

CONCLUSIONS

Linezolid and tedizolid alone are not optimal candidates to target bacterial phenotypes associated with chronic forms of BJI. Despite weak intracellular activity, they both reduce infection-related cytotoxicity, suggesting a role in modulating intracellular expression of staphylococcal virulence factors. Although inactive against biofilm-embedded S. aureus, both-but particularly tedizolid-are able to prevent biofilm formation.

Sustainable release of vancomycin from micro-arc oxidised 3D-printed porous Ti6Al4V for treating methicillin-resistant Staphylococcus aureus bone infection and enhancing osteogenesis in a rabbit tibia osteomyelitis model

Elimination of infection and enhancement of osteogenesis by orthopaedic implants are two critical factors in the treatment of complex bone infections. A prolonged and expensive procedure requiring two surgical steps and a 6-8-week period of joint immobilisation is utilised as a primary treatment for revision arthroplasty of an infected prosthesis, greatly affecting long-term patient care for the ageing population. Here, we evaluated the effects of vancomycin-loaded in micro-arc oxidised (MAO) three-dimensional (3D) printed porous Ti6Al4V scaffolds on osteogenesis. This system showed a high loading capacity and sustained vancomycin release kinetics, as demonstrated using high-performance liquid chromatography. In vivo, 0.1 mL of 10⁸ colony forming units (CFU) methicillin-resistant Staphylococcus aureus was injected into the tibias of rabbits to induce severe osteomyelitis. Physical, haematological, radiographic, microbiological, and histopathological analyses were performed to evaluate the effects of treatment. Rabbits with vancomycin-loaded in MAO scaffolds showed the inhibition of bone infection and enhancement of osteogenesis, resulting in better outcomes than in the other groups. Overall, these findings demonstrated the potential of this 3D printed porous Ti6Al4V, with good osteogenesis and sustained vancomycin release properties, for application in the treatment of complex bone infections.

Effect of Dalbavancin on Staphylococcal Biofilms When Administered Alone or in Combination With Biofilm-Detaching Compounds

Microorganisms grown in biofilms are more resistant to antimicrobial treatment and immune system attacks compared to their planktonic forms. In fact, infections caused by biofilm-forming Staphylococcus aureus and Staphylococcus epidermidis are a large threat for public health, including patients with medical devices. The aim of the current manuscript was to test the effect of dalbavancin, a recently developed lipoglycopeptide antibiotic, alone or in combination with compounds contributing to bacterial cell disaggregation, on staphylococcal biofilm formation and elimination. We used real-time impedance measurements in microtiter plates to study biofilm growth dynamics of S. aureus and S. epidermidis strains, in the absence or presence of dalbavancin, linezolid, vancomycin, cloxacillin, and rifampicin. Further experiments were undertaken to check whether biofilm-detaching compounds such as N-acetylcysteine (NAC) and ficin could enhance dalbavancin efficiency. Real-time dose–response experiments showed that dalbavancin is a highly effective antimicrobial, preventing staphylococcal biofilm formation at low concentrations. Minimum biofilm inhibitory concentrations were up to 22 higher compared to standard E-test values. Dalbavancin was the only antimicrobial that could halt new biofilm formation on established biofilms compared to the other four antibiotics. The addition of NAC decreased dalbavancin efficacy while the combination of dalbavancin with ficin was more efficient than antibiotic alone in preventing growth once the biofilm was established. Results were confirmed by classical biofilm quantification methods such as crystal violet (CV) staining and viable colony counting. Thus, our data support the use of dalbavancin as a promising antimicrobial to treat biofilm-related infections. Our data also highlight that synergistic and antagonistic effects between antibiotics and biofilm-detaching compounds should be carefully tested in order to achieve an efficient treatment that could prevent both biofilm formation and disruption.

Eradication of Repeated Episodes of Coagulase-Negative Staphylococcus Peritonitis: a Multipronged Approach

Bacterial peritonitis continues to be a significant cause of morbidity and mortality in patients undergoing peritoneal dialysis. Episodes of peritonitis due to coagulase-negative staphylococci (CNS) are especially prone to relapse or repeat, often culminating in catheter removal and technique failure. This pattern is thought to be associated with the production of a biofilm that offers protection against antimicrobials and the host defense systems. We report the successful eradication of repeated episodes of CNS peritonitis using an aggressive multipronged therapeutic approach combining several antibiotics and a thrombolytic agent.

Nanoantibiotics: A Novel Rational Approach to Antibiotic Resistant Infections

Background:

The main drawbacks for using conventional antimicrobial agents are the development of multiple drug resistance due to the use of high concentrations of antibiotics for extended periods. This vicious cycle often generates complications of persistent infections, and intolerable antibiotic toxicity. The problem is that while all new discovered antimicrobials are effective and promising, they remain as only short-term solutions to the overall challenge of drug-resistant bacteria.

Objective:

Recently, nanoantibiotics (nAbts) have been of tremendous interest in overcoming the drug resistance developed by several pathogenic microorganisms against most of the commonly used antibiotics. Compared with free antibiotic at the same concentration, drug delivered via a nanoparticle carrier has a much more prominent inhibitory effect on bacterial growth, and drug toxicity, along with prolonged drug release. Additionally, multiple drugs or antimicrobials can be packaged within the same smart polymer which can be designed with stimuli-responsive linkers. These stimuli-responsive nAbts open up the possibility of creating multipurpose and targeted antimicrobials. Biofilm formation still remains the leading cause of conventional antibiotic treatment failure. In contrast to conventional antibiotics nAbts easily penetrate into the biofilm, and selectively target biofilm matrix constituents through the introduction of bacteria specific ligands. In this context, various nanoparticles can be stabilized and functionalized with conventional antibiotics. These composites have a largely enhanced bactericidal efficiency compared to the free antibiotic.

Conclusion:

Nanoparticle-based carriers deliver antibiotics with better biofilm penetration and lower toxicity, thus combating bacterial resistance. However, the successful adaptation of nanoformulations to clinical practice involves a detailed assessment of their safety profiles and potential immunotoxicity.

Enhanced antibacterial properties of orthopedic implants by titanium nanotube surface modification: a review of current techniques

Prosthesis-associated infections are one of the main causes of implant failure; thus it is important to enhance the long-term antibacterial ability of orthopedic implants. Titanium dioxide nanotubes (TNTs) are biomaterials with good physicochemical properties and biocompatibility. Owing to their inherent antibacterial and drug-loading ability, the antibacterial application of TNTs has received increasing attention. In this review, the process of TNT anodizing fabrication is summarized. Also, the mechanism and the influencing factors of the antibacterial property of bare TNTs are explored. Furthermore, different antibacterial strategies for carrying drugs, as well as modifications to prolong the antibacterial effect and reduce drug-related toxicity are discussed. In addition, antibacterial systems based on TNTs that can automatically respond to infection are introduced. Finally, the currently faced problems are reviewed and potential solutions are proposed. This review provides new insight on TNT fabrication and summarizes the most advanced antibacterial strategies involving TNTs for the enhancement of long-term antibacterial ability and reduction of toxicity.

Biofilm and methods of its eradication

Microorganisms occur in the natural environment in the form of planktonic or create biofilms, i.e. communities of cells surrounded by the extracellular matrix. This is possible due to the phenomenon of quorum sensing, i.e. the ability of microorganisms to estimate their own density and change the expression of genes in response to them. Within such a structure, microorganisms are protected against harmful environmental conditions, their metabolic profile and the level of expression of individual genes are also changed, which leads to an increase in the pathogenicity of organisms associated in the form of biofilms. They pose a huge threat to hospital patients because they are capable of residing abiotic surfaces, such as catheters and endoprostheses, and can cause infection. The current methods of combating microbes with antibiotics and fungicides lose their effectiveness, both due to the increasing drug resistance of clinically relevant strains, but also to the very properties of biofilms. This determines the need to search for new and effective methods (physical, chemical and biological) to eradicate biofilms

Antibacterial Activities of Aliphatic Polyester Nanocomposites with Silver Nanoparticles and/or Graphene Oxide Sheets

Aliphatic polyesters such as poly(lactic acid) (PLA), polycaprolactone (PCL) and poly(lactic-co-glycolic) acid (PLGA) copolymers have been widely used as biomaterials for tissue engineering applications including: bone fixation devices, bone scaffolds, and wound dressings in orthopedics. However, biodegradable aliphatic polyesters are prone to bacterial infections due to the lack of antibacterial moieties in their macromolecular chains. In this respect, silver nanoparticles (AgNPs), graphene oxide (GO) sheets and AgNPs-GO hybrids can be used as reinforcing nanofillers for aliphatic polyesters in forming antimicrobial nanocomposites. However, polymeric matrix materials immobilize nanofillers to a large extent so that they cannot penetrate bacterial membrane into cytoplasm as in the case of colloidal nanoparticles or nanosheets. Accordingly, loaded GO sheets of aliphatic polyester nanocomposites have lost their antibacterial functions such as nanoknife cutting, blanket wrapping and membrane phospholipid extraction. In contrast, AgNPs fillers of polyester nanocomposites can release silver ions for destroying bacterial cells. Thus, AgNPs fillers are more effective than loaded GO sheets of polyester nanocomposiites in inhibiting bacterial infections. Aliphatic polyester nanocomposites with AgNPs and AgNPs-GO fillers are effective to kill multi-drug resistant bacteria that cause medical device-related infections.

Contribution of the serine protease HtrA in Escherichia coli to infection in foxes

Escherichia coli can cause severe, acute hemorrhagic pneumonia and systemic infection in farmed foxes, raccoon dogs and minks, leading to considerable economic losses to the farmers. It is well established that the htrA-encoded serine protease HtrA is critical for bacterial growth and survival under stress, and HtrA has been determined to be a potential vaccine target. However, the roles of HtrA in E. coli pathogenesis remain unknown. In this study, we generated an htrA-deletion mutant of the E. coli protype strain HBCLE-12 that causes pneumonia in silver foxes and then evaluated the changes in bacterial physiological characteristics in the absence of HtrA. The data show that knockout of the htrA gene did not affect growth and biochemical characteristics but led to impaired virulence of the strain. Increased susceptibility to environmental stresses, impaired survival in serum, and reduced biofilm formation may contribute to the virulence attenuation of the mutant. Furthermore, the HtrA-deficient mutant was subjected to RNA-seq analysis, and 16 differentially expressed genes were determined. This study provided insight that HtrA plays a definitive role in E. coli-induced infection.

Bone penetration of daptomycin in diabetic patients with bacterial foot infections

OBJECTIVES

Daptomycin has shown clinical efficacy in diabetic foot infections (DFI). However, only limited data are available on its bone penetration in this particular population. The aim of this study was to determine daptomycin bone concentrations in patients with DFI undergoing surgery after multiple daptomycin infusions and to determine bone daptomycin inhibitory quotients (IQs) for the predominant gram-positive species involved in DFI.

METHODS

Fourteen adult patients hospitalized with DFI treated with daptomycin and requiring surgical bone debridement and amputation were included in this single-centre prospective study. Daptomycin concentrations in serum and bone were determined by HPLC at steady state. Bone IQs were then calculated according to different minimum inhibitory concentrations (MICs; range 0.25-4mg/l) that are representative of the main MICs for Staphylococcus aureus, coagulase-negative staphylococci (CoNS), and Enterococcus sp populations.

RESULTS

Residual and peak concentrations varied from 4.5mg/l to 39.9mg/l and from 31.8mg/l to 110.9mg/l, respectively. Bone daptomycin concentrations at the moment of surgery varied from 1.2mg/l to 17mg/l. Up to a MIC of 1mg/l, which is the epidemiological cut-off value (ECOFF) and breakpoint value for S. aureus and CoNS, all bone daptomycin IQs were positive. The highest bone IQs were observed with Staphylococcus species. Calculated bone IQs for Enterococcus species were often weak at MIC values near the ECOFF.

CONCLUSIONS

Daptomycin penetrates bone well in patients treated for DFI. At an initially recommended dosage of 6mg/kg, bone concentrations are likely to be effective against staphylococcal infections and infections due to low-MIC Enterococcus.

Isothermal Microcalorimetry Detects the Presence of Persister Cells in a Staphylococcus aureus Biofilm After Vancomycin Treatment

Staphylococcus aureus biofilm plays a major role in implant-associated infections. Here, the susceptibility of biofilm S. aureus to daptomycin, fosfomycin, vancomycin, trimethoprim/sulfamethoxazole, linezolid, and rifampicin was investigated by isothermal microcalorimetry (IMC). Moreover, the persister status of cells isolated from S. aureus biofilm after treatment with vancomycin was also analyzed. S. aureus biofilm was tolerant to all the antibiotics tested [minimum biofilm bactericidal concentration (MBBC) > 256 μg/ml], except to daptomycin [MBBC and minimum biofilm eradicating concentration (MBEC) = 32 μg/ml] and rifampin (MBBC and MBEC = 128 μg/ml). After the treatment of MRSA biofilm with 1024 μg/ml vancomycin, ∼5% cells survived, although metabolically inactive (persisters). Interestingly, IMC revealed that persister bacteria reverted to a normal-growing phenotype when inoculated into fresh medium without antibiotics. A staggered treatment of MRSA biofilm with vancomycin to kill all the metabolically active cells and daptomycin to kill persister cells eradicated the whole bacterial population. These results support the use in the clinical practice of a therapeutic regimen based on the use of two antibiotics to kill persister cells and eradicate MRSA biofilms. IMC represents a suitable technique to characterize in real-time the reversion from persister to metabolically-active cells.

Treatment of late bacterial infections resulting from soft-tissue filler injections

Purpose

Late bacterial infections (LBIs) after esthetic facial augmentation using hyaluronic acid (HA) fillers are relatively rare yet severe complications that are difficult to treat. No adequate treatment standards have hitherto been formulated. We have bridged this gap by formulating a treatment scheme based on the principles of treating foreign-body implantation-related infections and treating bacterial growth in the form of biofilm. The objective of this study was to evaluate the efficacy of a comprehensive scheme for treating LBI complications after facial augmentation using cross-linked HA fillers.

Methods

A total of 22 patients with LBI symptoms at a site of cross-linked HA injection underwent treatment and observation. The comprehensive treatment scheme formulated by Marusza and Netsvyetayeva (M&N scheme) comprised draining the lesion, dissolution of cross-linked HA with hyaluronidase, broad-spectrum antibiotic combination therapy, and use of probiotics. While 17 patients underwent the M&N scheme, the remaining five were treated with other schemes. Statistical analysis of the data was performed using Mann–Whitney U and χ² nonparametric tests with SAS 9.4 software.

Results

All 17 patients who underwent the M&N scheme experienced resolution of symptoms, with no recurrence of infection at the HA-injection sites.

Conclusion

To treat LBI at a site of cross-linked HA administration, the principles applicable to infections resulting from implantation of a foreign body must be followed. The treatment period should be sufficiently long for complete resolution of symptoms. The efficacy of treatment is considered proven if 2 months have elapsed without recurrence since the symptoms resolved. The M&N scheme is recommended for use as the first therapeutic option for treating LBI related to soft-tissue fillers.

Role of Rifampin against Staphylococcal Biofilm Infections In Vitro, in Animal Models, and in Orthopedic-Device-Related Infections

Rifampin has been used as an agent in combination therapy in orthopedic device-related infections (ODRI) for almost three decades. The aim of this review is to provide data regarding the role of rifampin against biofilm infection in vitro, in animal models, and in clinical ODRI. Available data are gathered in order to present the rational use of rifampin combinations in patients with periprosthetic joint infection (PJI). The role of rifampin is well defined in patients with PJI and is indicated in those who fulfill the Infectious Diseases Society of America criteria for debridement and implant retention or one-stage exchange. It should be used with care because of the danger of rapid emergence of resistance. Potential drug interactions should be considered.

In Vitro Evaluation of Antimicrobial Activity and Cytotoxicity of Different Nanobiotics Targeting Multidrug Resistant and Biofilm Forming Staphylococci

Antibiotic-resistant and biofilm-forming bacteria have surprisingly increased over recent years. On the contrary, the rate of development of new antibiotics to treat these emerging superbugs is very slow. Therefore, the aim of this study was to prepare novel nanobiotic formulations to improve the antimicrobial activity of three antibiotics (linezolid, doxycycline, and clindamycin) against Staphylococci. Antibiotics were formulated as nanoemulsions and evaluated for their antimicrobial activities and cytotoxicities. Cytotoxicity of the conventional antibiotics and nanobiotics was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on rat hepatocytes. Half-maximal inhibitory concentration (IC₅₀) was estimated from an experimentally derived dose-response curve for each concentration using GraphPad Prism software. Upon quantitative assessment of Staphylococcus biofilm formation, eighty-four isolates (66.14 %) were biofilm forming. Linezolid and doxycycline nanobiotics exhibited promising antibacterial activities. On the contrary, clindamycin nanobiotic exhibited poor antibacterial activity. Minimum biofilm inhibitory concentrations showed that 73.68 %, 45.6%, and 5.2% of isolates were sensitive to linezolid, doxycycline, and clindamycin nanobiotics, respectively. Results of this study revealed that antibiotics loaded in nanosystems had a higher antimicrobial activity and lower cytotoxicities as compared to those of conventional free antibiotics, indicating their potential therapeutic values.

Bone Environment Influences Irreversible Adhesion of a Methicillin-Susceptible Staphylococcus aureus Strain

Prosthesis and joint infections are an important threat in public health, especially due to the development of bacterial biofilms and their high resistance to antimicrobials. Biofilm-associated infections increase mortality and morbidity rates as well as hospitalization costs. Prevention is the best strategy for this serious issue, so there is an urgent need to understand the signals that could induce irreversible bacterial adhesion on a prosthesis. In this context, we investigated the influence of the bone environment on surface adhesion by a methicillin-susceptible Staphylococcus aureus strain. Using static and dynamic biofilm models, we tested various bone environment factors and showed that the presence of Mg²⁺, lack of oxygen, and starvation each increased bacterial adhesion. It was observed that human osteoblast-like cell culture supernatants, which contain secreted components that would be found in the bone environment, increased bacterial adhesion capacity by 2-fold (p = 0.015) compared to the medium control. Moreover, supernatants from osteoblast-like cells stimulated with TNF-α to mimic inflammatory conditions increased bacterial adhesion by almost 5-fold (p = 0.003) without impacting on the overall biomass. Interestingly, the effect of osteoblast-like cell supernatants on bacterial adhesion could be counteracted by the activity of synthetic antibiofilm peptides. Overall, the results of this study demonstrate that factors within the bone environment and products of osteoblast-like cells directly influence S. aureus adhesion and could contribute to biofilm initiation on bone and/or prosthetics implants.

Protective effect of N-acetylcysteine in prosthetic joint infection: A nationwide population-based cohort study

PURPOSE

This nationwide population-based retrospective cohort study evaluated the protective effect of N-acetylcysteine against prosthetic joint infection after hip or knee joint replacement.

METHODS

Patients receiving N-acetylcysteine after hip or knee joint replacement between 2000 and 2015 were identified from the Taiwan National Health Insurance Research Database. Each patient receiving N-acetylcysteine was matched to four controls based on age, sex, and index year. All subjects were followed-up from the index date to December 31, 2015. The Cox proportional hazards regression model was used to assess the risk of prosthetic joint infection.

RESULTS

A total of 1478 patients were included in the study group, and 5912 matched subjects not receiving N-acetylcysteine were included in the control group. After adjusting for age, sex, insured premium, comorbidities, and immunosuppressive agent use, no significant difference in the risk of prosthetic joint infection was found between the two groups. A higher N-acetylcysteine dose (>360 cumulative defined daily dose) significantly decreased the risk of prosthetic joint infection (adjusted hazard ratio = 0.891; 95% confidence interval = 0.599-0.989; p = 0.042). The protective effect of N-acetylcysteine was observed only in the group of prosthetic joint infection within 5 years (adjusted hazard ratio = 0.801; 95% confidence interval = 0.581-0.980; p = 0.040).

CONCLUSIONS

High cumulative dose of N-acetylcysteine (>360 cumulative defined daily dose) can effectively reduce the risk of prosthetic joint infection in patients undergoing knee or hip joint replacement surgery within 5 years.

Indications and Guidelines for Debridement and Implant Retention for Periprosthetic Hip and Knee Infection

PURPOSE OF REVIEW

Prosthetic joint infection is one the most common causes of revision surgery after hip or knee replacement. Debridement and implant retention (DAIR) is one method of treating these infections; however, significant controversy exists. The purpose of our review was to describe current knowledge about indications, intraoperative/postoperative patient management, and outcomes of DAIR.

RECENT FINDINGS

Patient selection affects the success of DAIR. Medical comorbidities, duration of symptoms, and nature of infectious organism all influence outcomes. Intraoperative techniques such as open arthrotomy, extensive debridement, copious irrigation, and exchange of modular parts remain current standards for DAIR. Postoperative administration of antibiotics tailored to operative cultures remains critical. Antibiotic suppression may increase the success of DAIR. DAIR provides reasonable infection eradication between 50 and 80% with improved outcomes in appropriately selected patients. More research is needed on the use of adjuvant therapies intraoperatively and the role of postoperative antibiotic suppression.

Periprosthetic bacterial biofilm and quorum sensing

Periprosthetic joint infection (PJI) is a common complication after total joint arthroplasty leading to severe morbidity and mortality. With an aging population and increasing prevalence of total joint replacement procedures, the burden of PJI will be felt not only by individual patients, but in increased healthcare costs. Current treatment of PJI is inadequate resulting in incredibly high failure rates. This is believed to be largely mediated by the presence of bacterial biofilms. These polymicrobial bacterial colonies form within secreted extracellular matrices, adhering to the implant surface and local tissue. The biofilm architecture is believed to play a complex and critical role in a variety of bacterial processes including nutrient supplementation, metabolism, waste management, and antibiotic and immune resistance. The establishment of these biofilms relies heavily on the quorum sensing communication systems utilized by bacteria. Early stage research into disrupting bacterial communication by targeting quorum sensing show promise for future clinical applications. However, prevention of the biofilm formation via early forced induction of the biofilm forming process remains yet unexplored. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2331-2339, 2018.

Demonstration of the bactericidal effects of the boron neutron capture reaction

This pilot study represents a paradigm shift, using BNCT for the treatment of bacterial overgrowth on surgically implanted medical devices. In this study, titanium diboride disks were inoculated with S. aureus and irradiated in a thermal neutron beam. After a delivery of 2.6 × 10¹² n/cm² the surviving fraction of S. aureus on an irradiated disk was 3.1 × 10^-5 when compared with non-irradiated controls. This pilot study demonstrates proof of principle of boron neutron capture therapy for infection control (BNCIC).

Cost-benefit analysis of antibiofilm microbiological techniques for peri-prosthetic joint infection diagnosis

BACKGROUND

Implant-related infections, including those of peri-prosthetic joint (PJIs), osteosynthesis and other biomaterials, are biofilm-related. Pathogen identification is considered the diagnostic benchmark; however, the presence of bacterial biofilms makes pathogen detection with traditional microbiological techniques only partially effective. To improve microbiological diagnostic accuracy, some biofilm debonding techniques have been recently proposed. Aim of this health economics assessment study was to evaluate their economic impact on hospital costs.

METHODS

Direct and indirect hospital costs connected with the routine introduction of sonication and dithiothreitol treatment applied to hip and knee PJIs and of tissue cultures were examined. In particular the consequences of diagnostic inaccuracy, the opportunities, costs, and risks of each technique were calculated.

RESULTS

Considering an average of five samples per patient, processed separately with traditional tissue culture with or without sonication of prosthetic components, or pooled together using the MicroDTTect device (a close system for sample collection, transport and treatment with Dithiothreitol for microbial release from biofilm), the overall mean direct cost per patient was € 397 and € 393 for sonication or MicroDTTect, respectively, compared to € 308 for traditional tissue cultures. In terms of opportunity costs, MicroDTTect was the most effective technique, allowing for a 35% or 55% reduction in time required for sample treatment, compared to tissue cultures combined or not with sonication, respectively. Pooling together direct and indirect costs associated with false positive and negative results of the different diagnostic techniques, unnecessary medical treatments and possible medical claims, MicroDTTect or sonication become increasingly cost-effective when the extra-costs, generated by diagnostic inaccuracy of traditional tissue culture, took place, respectively, in 2% or 20% or more of the patients.

CONCLUSIONS

This is the first study specifically focused on the economic impact of the routine clinical use of microbiological antibiofilm sampling and processing techniques in orthopaedics. Although our results may suffer from a potential country and hospital bias, as the data collection process for direct and indirect costs is specific to each institution and country, this analysis highlights the potential economic advantage to hospitals associated with the routine introduction of antibiofilm techniques for microbiological diagnosis of PJI.

Current review-The rise of bacteriophage as a unique therapeutic platform in treating peri-prosthetic joint infections

Peri-prosthetic joint infection (PJI) is one of the most serious and dreaded complications after total joint replacement (TJR). Due to an aging population and the constant rise in demand for TJR, the incidence of PJI is also increasing. Successful treatment of PJI is challenging and is associated with high failure rates. One of the main causes for treatment failure is bacterial biofilm formation on implant surfaces and the adherence of biofilm bacteria on tissue and bone next to the implant. Biofilms are protective shields to bacterial cells and possess many unique properties that leads to antibiotic resistance. New therapeutic platforms are currently being explored to breakdown biofilm matrix in order to enhance the efficacy of antibiotics. Bacteriophages (phages) is one of these unique therapeutic platforms that can degrade biofilms as well as target the killing of bacterial cells. Preclinical studies of biofilm-mediated infections have demonstrated the ability of phage to eradicate biofilms and clear infections by working synergistically with antibiotics. There is strong preclinical evidence that phage can reduce the concentration of antibiotics required to treat an infection. These findings support a promising role for phages as a future clinical adjunct to antibiotics. In addition, phage therapy can be personalized to target a specific bacterial strain. Clinical studies using phage therapy are limited in Western literature; but phase I studies have established good safety profile with no adverse outcomes reported. In order to translate phage therapy to treat PJI in clinics, further preclinical testing is still required to study optimal delivery methods as well as the interaction between phage and the immune system in vivo. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1051-1060, 2018.

Phenylthiazoles with tert-Butyl side chain: Metabolically stable with anti-biofilm activity

A new series of phenylthiazoles with t-butyl lipophilic component was synthesized and their antibacterial activity against a panel of multidrug-resistant bacterial pathogens was evaluated. Five compounds demonstrated promising antibacterial activity against methicillin-resistant staphylococcal strains and several vancomycin-resistant staphylococcal and enterococcal species. Additionally, three derivatives 19, 23 and 26 exhibited rapid bactericidal activity, and remarkable ability to disrupt mature biofilm produced by MRSA USA300. More importantly, a resistant mutant to 19 couldn't be isolated after subjecting MRSA to sub-lethal doses for 14 days. Lastly, this new series of phenylthiazoles possesses an advantageous attribute over the first-generation compounds in their stability to hepatic metabolism, with a biological half-life of more than 9 h.

Effect of hyperbaric oxygen therapy (HBO) on implant-associated osteitis in a femur fracture model in mice

Hyperbaric oxygen therapy (HBO) is applied very successfully in treatment of various diseases such as chronic wounds. It has been already suggested as adjunctive treatment option for osteitis by immune- and fracture modulating effects. This study evaluates the importance of HBO in an early implant-associated localized osteitis caused by Staphylococcus aureus (SA) compared to the standard therapy. In a standardized murine model the left femur of 120 BALB/c mice were osteotomized and fixed by a titanium locking plate. Osteitis has been induced with a defined amount of SA into the fracture gap. Debridément and lavages were progressed on day 7, 14, 28 and 56 to determine the local bacterial growth and the immune reaction. Hyperbaric oxygen (2 ATA, 90%) was applied for 90 minutes on day 7 to 21 for those mice allocated to HBO therapy. To evaluate the effect of HBO therapy the following groups were analyzed: Two sham-groups (12 mice / group) with and without HBO therapy, two osteotomy groups (24 mice / group) with plate osteosynthesis of the femur with and without HBO therapy, and two osteotomy SA infection groups (24 mice / group) with and without HBO therapy. Fracture healing was also quantified on day 7, 14, 28 and 56 by a.p. x-ray and bone healing markers from blood samples. Progression of infection was assessed by estimation of colony-forming units (CFU) and immune response was analyzed by determination of polymorphonuclear neutrophils (PMN), Interleukin (IL) - 6, and the circulating free DNA (cfDNA) in lavage samples. Osteitis induced significantly higher IL-6, cfDNA- and PMN-levels in the lavage samples (on day 7 and 14, each p < 0.05). HBO-therapy did not have a significant influence on the CFU and immune response compared to the standard therapy (each p > 0.05). At the same time HBO-therapy was associated with a delayed bone healing assessed by x-ray radiography and a higher rate of non-union until day 28. In conclusion, osteitis led to significantly higher bacterial count and infection parameters. HBO-therapy neither had a beneficial influence on local infection nor on immune response or fracture healing compared to the standard therapy in an osteitis mouse model.

Phage-derived lysins as potential agents for eradicating biofilms and persisters

Bacterial biofilms are highly resistant to the action of antibiotics. Presence of persisters, phenotypically resistant populations of bacterial cells, is thought to contribute toward recalcitrance of biofilms. The phage-derived lysins, by virtue of their ability to cleave the peptidoglycan of bacterial cells in an enzymatic manner, have the unique ability to kill dormant cells. Several lysins have shown potent antibiofilm activity in vitro. The fact that lysins have shown better efficacy than conventional drugs in animal models of endocarditis and other infections involving biofilms suggests that the lysins can potentially be developed against difficult-to-treat bacterial infections.

How Many Cultures Are Necessary to Identify Pathogens in the Management of Total Hip and Knee Arthroplasty Infections?

BACKGROUND

Identification of the infecting organism is critical to the successful management of deep prosthetic joint infections about the hip and the knee. However, the number of culture specimens and which culture specimens are best to identify these organisms is unknown.

METHODS

We evaluated 113 consecutive patients with infected total hip and total knee arthroplasties and correlated the type of culture specimen and number of specimens taken during surgery to the likelihood of a positive culture result. From these data, we subsequently developed a model to maximize culture yield at the time of surgical intervention. After exclusions, 74 patients meeting the Musculoskeletal Infection Society criteria were left for final analysis.

RESULTS

From this cohort, 63 of 74 patients had a positive culture result (85%). The odds of a fluid culture result being positive was 35 of 47 (0.75), whereas the likelihood of tissue cultures yielding a positive result was 164 of 245 (0.67; P = .313). The sample designated "best culture" specimen was the only culture with a positive result in 1 of 48 cases in which a best culture was identified. The optimal number of cultures needed to yield a positive test result was 4 (specificity = 0.61 and sensitivity = 0.63). Increasing the number of samples increases sensitivity but reduces specificity.

CONCLUSION

A minimum of 4 tissue cultures from representative areas is necessary to maximize the chance of identifying the infecting organism during management of the infected total hip and total knee arthroplasties. The designation of the best culture specimen for additional testing is arbitrary and may not be clinically efficacious.

Efficacy of Open Debridement and Polyethylene Exchange in Strictly Selected Patients with Infection after Total Knee Arthroplasty

Purpose

To assess the efficacy of open debridement and polyethylene exchange (ODPE) combined with proper antibiotic therapy in strictly selected patients with infection after total knee arthroplasty (TKA) and analyze factors associated with treatment failure.

Materials and Methods

From January 2010 to January 2014, 25 cases that underwent ODPE under the diagnosis of infection within four weeks after TKA or acute hematogenous infection within five days of symptom onset were reviewed in this study.

Results

Treatment was successful in 22 out of 25 cases (88.0%). Factors associated with failure were accompanying infection (periprosthetic infection in the ipsilateral foot, cervical parotid abscess, and masticator space abscess) and diagnosis of rheumatoid arthritis (RA) before TKA. Resistant bacteria did not entail a risk. On clinical results, the mean postoperative Lysholm score and Korean Knee score were 81.4 and 79.4, respectively, the knee range of motion was 115.4°±12.9°, and duration of hospitalization was 32.3±8.4 days. On radiographic results, 3.47±1.56 mm joint line elevation and a valgus change of 0.61°±2.35° in knee alignment were observed.

Conclusions

ODPE combined with appropriate antibiotics therapy could be a useful treatment method for infection after TKA if the procedure is performed within a symptom duration of five days or less in the absence of accompanying infection in patients whose indication for TKA was not RA.

The Staphylococcal Biofilm: Adhesins, Regulation, and Host Response

The staphylococci comprise a diverse genus of Gram-positive, nonmotile commensal organisms that inhabit the skin and mucous membranes of humans and other mammals. In general, staphylococci are benign members of the natural flora, but many species have the capacity to be opportunistic pathogens, mainly infecting individuals who have medical device implants or are otherwise immunocompromised. Staphylococcus aureus and Staphylococcus epidermidis are major sources of hospital-acquired infections and are the most common causes of surgical site infections and medical device-associated bloodstream infections. The ability of staphylococci to form biofilms in vivo makes them highly resistant to chemotherapeutics and leads to chronic diseases. These biofilm infections include osteomyelitis, endocarditis, medical device infections, and persistence in the cystic fibrosis lung. Here, we provide a comprehensive analysis of our current understanding of staphylococcal biofilm formation, with an emphasis on adhesins and regulation, while also addressing how staphylococcal biofilms interact with the immune system. On the whole, this review will provide a thorough picture of biofilm formation of the staphylococcus genus and how this mode of growth impacts the host.

Kinetics of biofilm formation by Staphylococcus lugdunensis strains in bone and joint infections

OBJECTIVE

To describe the clinical presentation and 1-year follow-up of patients with bone and joint infections (BJIs) caused by Staphylococcus lugdunensis and evaluate its biofilm-forming capacities.

PATIENTS AND METHODS

Overall, 28 patients with BJIs from VISLISI clinical trials were included. We evaluated 1-year clinical follow-up and analyzed biofilm production kinetics of the 28 strains using the BioFilm Ring Test®.

RESULTS

Of all patients, 12 had osteoarticular infections without material and 16 had prosthetic joint infections, of which 9 underwent a 1-stage revision procedure. At the 1-year follow-up, all patients were cured but needed a surgical intervention. Diabetes affected 46.4% of all patients. Of all, 20 strains (71.4%) started biofilm formation within 2 h, but all strains started the formation after 4 h experiment, and 25 strains (89.3%) reached a maximum after 6 h.

CONCLUSIONS

This study describes the clinical and surgical management of BJIs caused by S. lugdunensis and shows that 1-stage prosthesis exchange procedures may be efficient. Further, It shows that biofilm production by this strain was not marginal and directly impacted clinical and surgical management.

Prolonged suppressive antibiotic therapy for prosthetic joint infection in the elderly: a national multicentre cohort study

During prosthetic joint infection (PJI), optimal surgical management with exchange of the device is sometimes impossible, especially in the elderly population. Thus, prolonged suppressive antibiotic therapy (PSAT) is the only option to prevent acute sepsis, but little is known about this strategy. We aimed to describe the characteristics, outcome and tolerance of PSAT in elderly patients with PJI. We performed a national cross-sectional cohort study of patients >75 years old and treated with PSAT for PJI. We evaluated the occurrence of events, which were defined as: (i) local or systemic progression of the infection (failure), (ii) death and (iii) discontinuation or switch of PSAT. A total of 136 patients were included, with a median age of 83 years [interquartile range (IQR) 81-88]. The predominant pathogen involved was Staphylococcus (62.1%) (Staphylococcus aureus in 41.7%). A single antimicrobial drug was prescribed in 96 cases (70.6%). There were 46 (33.8%) patients with an event: 25 (18%) with an adverse drug reaction leading to definitive discontinuation or switch of PSAT, 8 (5.9%) with progression of sepsis and 13 died (9.6%). Among patients under follow-up, the survival rate without an event at 2 years was 61% [95% confidence interval (CI): 51;74]. In the multivariate Cox analysis, patients with higher World Health Organization (WHO) score had an increased risk of an event [hazard ratio (HR) = 1.5, p = 0.014], whereas patients treated with beta-lactams are associated with less risk of events occurring (HR = 0.5, p = 0.048). In our cohort, PSAT could be an effective and safe option for PJI in the elderly.

In vitro and in vivo drug release and antibacterial properties of the novel vancomycin-loaded bone-like hydroxyapatite/poly amino acid scaffold

Antibiotic-loaded carriers were developed to fill cavities and locally deliver antibiotics following implantation. However, the most commonly used antibiotic carrier, polymethyl methacrylate (PMMA), has many disadvantages including that it does not promote bone regeneration or conduction. Vancomycin-loaded bone-like hydroxyapatite/poly amino acid (V-BHA/PAA) was successfully fabricated by a homogeneous method, certified as biosafe and known to promote osteogenesis. To evaluate its drug-release features, the quantity of the vancomycin in the elution was obtained every 2 days after in vitro simulated body fluid immersion. The drug concentration in the elution was determined to obtain the drug-release curve. The in vitro drug release was a three-phase process with two release peaks. Its antibacterial activity was evaluated in vitro using an antibacterial zone assay, antibacterial inhibition, and scanning electron microscopy (SEM) observation. Scaffolds of V-BHA/PAA were implanted into a rabbit model of chronic osteomyelitis. The antibacterial activity of the material was evaluated in vivo by gross observations, X-ray, and histological and ultrastructural observations. During the first 48 h, the vancomycin release was more rapid, followed by a period of sustained slow release. Use of V-BHA/PAA could achieve relatively long-term vancomycin delivery of 38 days in vitro and 42 days in vivo. V-BHA/PAA showed a significant and consistent bactericidal effect toward both Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) in vitro and in vivo. Moreover, the bactericidal effect was stronger than that of vancomycin-loaded polymethyl meth acrylate (V-PMMA). The duration of the antibacterial effect of V-BHA/PAA toward both S. aureus and MRSA exceeded 28 days in vitro, while that of V-PMMA lasted only 14 days. The curative rate for V-BHA/PAA in the chronic osteomyelitis model was 75% for regular S. aureus and 66.67% for MRSA infection, which significantly exceeded that of V-PMMA (50% and 41.67%, respectively). Vancomycin released from the V-BHA/PAA scaffold was significantly superior to that delivered by V-PMMA.

Osteomyelitis: Recent advances in pathophysiology and therapeutic strategies

This review article summarizes the recent advances in pathogenic mechanisms and novel therapeutic strategies for osteomyelitis, covering both periprosthetic joint infections and fracture-associated bone infections. A better understanding of the pathophysiology including the mechanisms for biofilm formation has led to new therapeutic strategies for this devastating disease. Research on novel local delivery materials with appropriate mechanical properties, lower exothermicity, controlled release of antibiotics, and absorbable scaffolding for bone regeneration is progressing rapidly. Emerging strategies for prevention, early diagnosis of low-grade infections, and innovative treatments of osteomyelitis such as biofilm disruptors and immunotherapy are highlighted in this review.

The role of biofilms in persistent infections and factors involved in ica-independent biofilm development and gene regulation in Staphylococcus aureus

Staphylococcus aureus biofilms represent a unique micro-environment that directly contribute to the bacterial fitness within hospital settings. The accumulation of this structure on implanted medical devices has frequently caused the development of persistent and chronic S. aureus-associated infections, which represent an important social and economic burden worldwide. ica-independent biofilms are composed of an assortment of bacterial products and modulated by a multifaceted and overlapping regulatory network; therefore, biofilm composition can vary among S. aureus strains. In the microniches formed by biofilms-produced by a number of bacterial species and composed by different structural components-drug refractory cell subpopulations with distinct physiological characteristics can emerge and result in therapeutic failures in patients with recalcitrant bacterial infections. In this review, we highlight the importance of biofilms in the development of persistence and chronicity in some S. aureus diseases, the main molecules associated with ica-independent biofilm development and the regulatory mechanisms that modulate ica-independent biofilm production, accumulation, and dispersion.

Treatment With Dithiothreitol Improves Bacterial Recovery From Tissue Samples in Osteoarticular and Joint Infections

BACKGROUND

Prosthetic implants, periprosthetic and osteoarticular tissues are specimens of choice for diagnosis of bone and joint infections. Homogenization is considered the best procedure for treatment of tissues samples, but, it is not always performed in all laboratories. Dithiothreitol (DTT) has been proposed as an alternative treatment to sonication for microbiological diagnosis of prosthetic joint infections. In this study, the applicability of DTT treatment for processing of periprosthetic and osteoarticular tissues for diagnosis of bone and joint infections was evaluated and compared with normal saline solution treatment.

METHODS

Periprosthetic tissue samples were collected from 70 consecutive patients (25 infected and 45 not infected). For each patient, samples from the same site were randomly allocated to DTT or saline treatment. Treated samples were centrifuged at 3000 rpm for 10 minutes. Aliquots from the concentrated samples were plated on agar plates and inoculated in broths. Sensitivity and specificity were calculated for each treatment.

RESULTS

Microbial growth was observed in samples from 14 and 11 infected patients after DTT and saline treatments, respectively. Concordance between the 2 methods was observed in the 85.7% of cases. Sensitivity was 88.0% for DTT and 72.0% for saline. Specificity was 97.8% and 91.1% for DTT and saline, respectively. Treatment with DTT showed higher sensitivity and specificity with respect to the method routinely used in our laboratory.

CONCLUSION

DTT treatment may be considered a practicable strategy for microbiological analysis of tissues for diagnosis of bone and joint infections.

Salvage Procedures for Management of Prosthetic Joint Infection After Hip and Knee Replacements

Background:

The increasing load placed by joint replacement surgery on health care systems makes infection, even with the lowest rates, a serious concern that needs to be thoroughly studied and addressed using all possible measures.

Methods:

A comprehensive review of the current literature on salvage procedures for recurrent PJIs using PubMed, EMBASE and CINAHL has been conducted.

Results:

Prolonged suppressive antibiotic therapy (PSAT), resection arthroplasty and arthrodesis were the most common procedures performed. Suppressive antibiotic therapy is based on the use of well tolerated long term antibiotics in controlling sensitive organisms. Resection arthroplasty which should be reserved as a last resort provided more predictable outcomes in the hip whereas arthrodesis was associated with better outcomes in the knee. Various methods for arthrodesis including internal and external fixation have been described.

Conclusion:

Despite good union and infection control rates, all methods were associated with complications occasionally requiring further surgical interventions.

Modulation of the Substitution Pattern of 5-Aryl-2-Aminoimidazoles Allows Fine-Tuning of Their Antibiofilm Activity Spectrum and Toxicity

We previously synthesized several series of compounds, based on the 5-aryl-2-aminoimidazole scaffold, that showed activity preventing the formation of Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa biofilms. Here, we further studied the activity spectrum of a number of the most active N1- and 2N-substituted 5-aryl-2-aminoimidazoles against a broad panel of biofilms formed by monospecies and mixed species of bacteria and fungi. An N1-substituted compound showed very strong activity against the biofilms formed by Gram-negative and Gram-positive bacteria and the fungus Candida albicans but was previously shown to be toxic against various eukaryotic cell lines. In contrast, 2N-substituted compounds were nontoxic and active against biofilms formed by Gram-negative bacteria and C. albicans but had reduced activity against biofilms formed by Gram-positive bacteria. In an attempt to develop nontoxic compounds with potent activity against biofilms formed by Gram-positive bacteria for application in antibiofilm coatings for medical implants, we synthesized novel compounds with substituents at both the N1 and 2N positions and tested these compounds for antibiofilm activity and toxicity. Interestingly, most of these N1-,2N-disubstituted 5-aryl-2-aminoimidazoles showed very strong activity against biofilms formed by Gram-positive bacteria and C. albicans in various setups with biofilms formed by monospecies and mixed species but lost activity against biofilms formed by Gram-negative bacteria. In light of application of these compounds as anti-infective coatings on orthopedic implants, toxicity against two bone cell lines and the functionality of these cells were tested. The N1-,2N-disubstituted 5-aryl-2-aminoimidazoles in general did not affect the viability of bone cells and even induced calcium deposition. This indicates that modulating the substitution pattern on positions N1 and 2N of the 5-aryl-2-aminoimidazole scaffold allows fine-tuning of both the antibiofilm activity spectrum and toxicity.

Development of an in vitro Assay, Based on the BioFilm Ring Test®, for Rapid Profiling of Biofilm-Growing Bacteria

Microbial biofilm represents a major virulence factor associated with chronic and recurrent infections. Pathogenic bacteria embedded in biofilms are highly resistant to environmental and chemical agents, including antibiotics and therefore difficult to eradicate. Thus, reliable tests to assess biofilm formation by bacterial strains as well as the impact of chemicals or antibiotics on biofilm formation represent desirable tools for a most effective therapeutic management and microbiological risk control. Current methods to evaluate biofilm formation are usually time-consuming, costly, and hardly applicable in the clinical setting. The aim of the present study was to develop and assess a simple and reliable in vitro procedure for the characterization of biofilm-producing bacterial strains for future clinical applications based on the BioFilm Ring Test® (BRT) technology. The procedure developed for clinical testing (cBRT) can provide an accurate and timely (5 h) measurement of biofilm formation for the most common pathogenic bacteria seen in clinical practice. The results gathered by the cBRT assay were in agreement with the traditional crystal violet (CV) staining test, according to the κ coefficient test (κ = 0.623). However, the cBRT assay showed higher levels of specificity (92.2%) and accuracy (88.1%) as compared to CV. The results indicate that this procedure offers an easy, rapid and robust assay to test microbial biofilm and a promising tool for clinical microbiology.

Anti-biofilm Activities from Resveratrol against Fusobacterium nucleatum

Fusobacterium nucleatum is a Gram-negative, anaerobic bacterium that plays an important role in dental plaque biofilm formation. In this study, we evaluate the effect of resveratrol, a phytoalexin compound, on F. nucleatum biofilm formation. The effects of different concentrations of resveratrol on biofilms formed on 96-well microtiter plates at different time points were determined by the MTT assay. The structures and thicknesses of the biofilm were observed by confocal laser scanning microscopy (CLSM), and gene expression was investigated by real-time PCR. The results showed that resveratrol at sub-MIC levels can significantly decrease biofilm formation, whereas it does not affect the bacterial growth rate. It was observed by CLSM images that the biofilm was visually decreased with increasing concentrations of resveratrol. Gene expression was down regulated in the biofilm in the presence of resveratrol. Our results revealed that resveratrol can effectively inhibit biofilm formation.

Rifamycins, Alone and in Combination

Rifamycins inhibit RNA polymerase of most bacterial genera. Rifampicin remains part of combination therapy for treating tuberculosis (TB), and for treating Gram-positive prosthetic joint and valve infections, in which biofilms are prominent. Rifabutin has use for AIDS patients in treating mycobacterial infections TB and Mycobacterium avium complex (MAC), having fewer drug-drug interactions that interfere with AIDS medications. Rifabutin is occasionally used in combination to eradicate Helicobacter pylori (peptic ulcer disease). Rifapentine has yet to fulfill its potential in reducing time of treatment for TB. Rifaximin is a monotherapeutic agent to treat gastrointestinal (GI) disorders, such as hepatic encephalopathy, irritable bowel syndrome, and travelers' diarrhea. Rifaximin is confined to the GI tract because it is not systemically absorbed on oral dosing, achieving high local concentrations, and showing anti-inflammatory properties in addition to its antibacterial activity. Resistance issues are unavoidable with all the rifamycins when the bioburden is high, because of mutations that modify RNA polymerase.

Preliminary results of a new antibiotic susceptibility test against biofilm installation in device-associated infections: the Antibiofilmogram®

Biofilms are complex communities of microorganisms embedded in an extracellular matrix and adherent to a surface. The development was described as a four-stage process leading to the formation of a mature biofilm which was resistant to immune system and antibiotic actions. In bone and joint infections (BJIs), the formation of biofilms is a leading cause of treatment failure. Here we study the capacity of 11 antibiotics commonly used in the treatment of BJIs to inhibit the biofilm formation on 29 clinical Staphylococcus aureus isolates by a new test called Antibiofilmogram(®) The minimal inhibitory concentration (MIC) and biofilm MIC (bMIC) were determined in vitro and showed similar values for clindamycin, fusidic acid, linezolid and rifampin. Reversely, daptomycin, fosfomycin, gentamicin and ofloxacin showed a bMIC distribution different from MIC with bMIC above breakpoint. Finally, cloxacillin, teicoplanin and vancomycin revealed an intermediate bMIC distribution with a strain-dependent pattern. A murine in vivo model of catheter-associated S. aureus infection was made and showed a significant reduction, but not total prevention, of catheter colonization with cloxacillin at bMIC, and no or limited reduction with cloxacillin at MIC. Antibiofilmogram(®) could be of great interest after surgical operations on contaminated prostheses and after bacteremia in order to prevent the colonization of the device.

Daptomycin > 6 mg/kg/day as salvage therapy in patients with complex bone and joint infection: cohort study in a regional reference center

Background

Even if daptomycin does not have approval for the treatment of bone and joint infections (BJI), the Infectious Diseases Society of America guidelines propose this antibiotic as alternative therapy for prosthetic joint infection. The recommended dose is 6 mg/kg/d, whereas recent data support the use of higher doses in these patients.

Methods

We performed a cohort study including consecutive patients that have received daptomycin >6 mg/kg/d for complex BJI between 2011 and 2013 in a French regional reference center. Factors associated with treatment failure were determined on univariate Cox analysis and Kaplan-Meier curves.

Results

Forty-three patients (age, 61 ± 17 years) received a mean dose of 8 ± 0.9 mg/kg/d daptomycin, for a mean 81 ± 59 days (range, 6–303 days). Most had chronic (n = 37, 86 %) implant-associated (n = 37, 86 %) BJI caused by coagulase-negative staphylococci (n = 32, 74 %). A severe adverse event (SAE) occurred in 6 patients (14 %), including 2 cases of eosinophilic pneumonia, concomitant with daptomycin C_min >24 mg/L. Outcome was favorable in 30 (77 %) of the 39 clinically assessable patients. Predictors for treatment failure were age, non-optimal surgery and daptomycin withdrawal for SAE.

Conclusions

Prolonged high-dose daptomycin therapy was effective in patients with complex BJI. However, optimal surgery remains the cornerstone of medico-surgical strategy; and a higher incidence of eosinophilic pneumonia than expected was recorded.

Multiplex Antibody Detection for Noninvasive Genus-Level Diagnosis of Prosthetic Joint Infection

We developed and evaluated a multiplex antibody detection-based immunoassay for the diagnosis of prosthetic joint infections (PJIs). Sixteen protein antigens from three Staphylococcus species (Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus lugdunensis) (8 antigens), Streptococcus agalactiae (4 antigens), and Propionibacterium acnes (4 antigens) were selected by comparative immunoproteomics using serum samples from PJI cases versus controls. A bead-based multiplex immunoassay that measured serum IgG against purified, recombinant forms of each of the 16 antigens was developed. We conducted a prospective study to evaluate the performance of the assay. A PJI was defined by the presence of a sinus tract and/or positive intraoperative sample cultures (at least one sample yielding a virulent organism or at least two samples yielding the same organism). A total of 455 consecutive patients undergoing revision or resection arthroplasty (hip, 66.3%; knee, 29.7%; shoulder, 4%) at two French reference centers for the management of PJI were included: 176 patients (38.7%) were infected and 279 (61.3%) were not. About 60% of the infections involved at least one of the species targeted by the assay. The sensitivity/specificity values were 72.3%/80.7% for targeted staphylococci, 75%/92.6% for S. agalactiae, and 38.5%/84.8% for P. acnes. The assay was more sensitive for infections occurring >3 months after arthroplasty and for patients with an elevated C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR). However, it detected 64.3% and 58.3% of targeted staphylococcal infections associated with normal CRP and ESR values, respectively. This new multiplex immunoassay approach is a novel noninvasive tool to evaluate patients suspected of having PJIs and provides information complementary to that from inflammatory marker values.