Comparative efficacies of quinupristin-dalfopristin, linezolid, vancomycin, and ciprofloxacin in treatment, using the antibiotic-lock technique, of experimental catheter-related infection due to Staphylococcus aureus

Bones on fire: illuminating osteomyelitis through the radiant lens of 18F-FDG PET/CT

Osteomyelitis is an inflammatory process that is caused by an infecting microorganism and leads to progressive bone destruction and loss. Osteomyelitis can occur at any age and can involve any bone. The infection can be limited to a single portion of the bone or can involve several regions, such as marrow, cortex, periosteum, and the surrounding soft tissue. Early and accurate diagnosis plays a crucial role in reducing unnecessary treatment measures, improving the patient's prognosis, and minimizing time and financial costs. In recent years, the use of functional metabolic imaging has become increasingly widespread. Among them, 18F-FDG PET/CT has emerged as a cutting-edge imaging modality that combines anatomical and functional metabolic information. It has seen rapid development in the field of infectious diseases. 18F-FDG PET/CT has been demonstrated to yield acceptable diagnostic accuracy in a number of infectious and inflammatory diseases. This review aims to provide information about the 18F-FDGPET/CT in the use of chronic osteomyelitis,osteomyelitis secondary to a contiguous focus of infection and osteomyelitis associated with peripheral vascular disease.

Antimicrobial activity of antibiotics on biofilm formed by Staphylococcus aureus and Pseudomonas aeruginosa in an open microfluidic model mimicking the diabetic foot environment

BACKGROUND

Diabetic foot infections (DFIs) represent a public health problem because of their frequency and the severity of their consequences, i.e. amputation and mortality. Polymicrobial biofilms on the skin surface of these ulcers complicate wound healing. Few in vitro models exist to study the antibiotics activity in this context.

OBJECTIVES

This study evaluated the in vitro activity of antibiotics against the two main bacteria isolated in DFI, Staphylococcus aureus and Pseudomonas aeruginosa, using a dynamic system (BioFlux™ 200) and a chronic wound-like medium (CWM) that mimic the foot ulcer environment.

METHODS

Reference strains and two pairs of clinical S. aureus and P. aeruginosa isolated together from a DFI were cultivated in brain heart infusion and CWM media during 72 h at 37°C, alone and combined in the BioFlux™ 200 system. Antibiotic activity was evaluated after a mechanical debridement. The activities were measured by the reduction of biofilm percentage of bacteria in the microfluidic system using microscopy.

RESULTS

Daptomycin for S. aureus and ceftazidime for P. aeruginosa showed excellent activity to reduce biofilm biomass, whereas linezolid action was more mitigated and dalbavancin was ineffective. Ceftazidime + daptomycin presented the most potent in vitro activity on a mixed biofilm.

CONCLUSIONS

The combination of CWM and the BioFlux™ microfluidic system represents a valuable tool to screen the potential antimicrobial activity of antibiotics under conditions mimicking those encountered in DFI. It could help clinicians in their management of chronic wounds.

Role of Extracellular DNA in Dalbavancin Activity against Methicillin-Resistant Staphylococcus aureus (MRSA) Biofilms in Patients with Skin and Soft Tissue Infections

Methicillin-resistant Staphylococcus aureus (MRSA) has become the leading cause of skin and soft tissue infections (SSTIs). Biofilm production further complicates patient treatment, contributing to increased bacterial persistence and antibiotic tolerance. The study aimed to explore the efficacy of different antibiotics on biofilm-producing MRSA isolated from patients with SSTI. A total of 32 MRSA strains were collected from patients with SSTI. The MIC and minimal biofilm eradication concentration (MBEC) were measured in planktonic and biofilm growth. The study showed that dalbavancin, linezolid, and vancomycin all inhibited MRSA growth at their EUCAST susceptible breakpoint. Of the MRSA strains, 87.5% (n = 28) were strong biofilm producers (SBPs), while only 12.5% (n = 4) were weak biofilm producers (WBPs). The MBEC90 values for dalbavancin were significantly lower than those of linezolid and vancomycin in all tested strains. We also found that extracellular DNA (eDNA) contributes to the initial microbial attachment and biofilm formation. The amount of eDNA differed among MRSA strains and was significantly higher in those isolates with high dalbavancin and vancomycin tolerance. Exogenously added DNA increased the MBEC90 and protection of biofilm cells from dalbavancin activity. Of note, the relative abundance of eDNA was higher in MRSA biofilms exposed to MBEC90 dalbavancin than in untreated MRSA biofilms and those exposed to sub-MIC90. Overall, dalbavancin was the most active antibiotic against MRSA biofilms at concentrations achievable in the human serum. Moreover, the evidence of a drug-related increase of eDNA and its contribution to antimicrobial drug tolerance reveals novel potential targets for antibiofilm strategies against MRSA. IMPORTANCE Staphylococcus aureus is the most common cause of skin and soft tissue infections (SSTIs) worldwide. In addition, methicillin-resistant S. aureus (MRSA) is increasingly frequent in postoperative infections and responsible for a large number of hospital readmissions and deaths. Biofilm formation by S. aureus is a primary risk factor in SSTIs, due to a higher antibiotic tolerance. Our study showed that the biofilm-forming capacity varied among MRSA strains, although strong biofilm producers were significantly more abundant than weak biofilm producer strains. Notably, dalbavancin demonstrated a potent antibiofilm activity at concentrations achievable in human serum. Nevertheless, dalbavancin activity was affected by an increased concentration of extracellular DNA in the biofilm matrix. This study provides novel insight for designing more targeted therapeutic strategies against MRSA and to prevent or eradicate harmful biofilms.

In vitro Activities of N-Acetyl Cysteine and Levofloxacin as a Catheter Lock Therapy against Catheter-Associated Infections

AIMS

Since management of catheter-associated infections, which are generally biofilm-based, is attempted in certain patients such as older and frail patients by using a catheter lock solution (CLS), we examined the combination of N-acetyl cysteine (NAC), an antibiofilm agent, and levofloxacin, a broad-spectrum antimicrobial agent, for this purpose.

METHODS AND RESULTS

Intravascular catheters were colonized with methicillin-resistant Staphylococcus epidermidis, levofloxacin-sensitive/methicillin-resistant S. aureus, levofloxacin-resistant/methicillin-resistant S. aureus, vancomycin-resistant Enterococcus, Escherichia coli, Klebsiella pneumoniae, or Pseudomonas aeruginosa and treated with a CLS containing normal saline, NAC, levofloxacin, or NAC plus levofloxacin (NACLEV) and then cultured to assess their antimicrobial activities. We also examined antibiofilm and antimicrobial activities of each CLS by scanning electron microscopy (SEM) and the mechanical integrity of catheters exposed to CLS. Treatment of colonized catheters with NACLEV-CLS significantly reduced colonization (P < 0.005) against all pathogens. SEM images also indicate reduction in colonization with NACLEV-CLS with considerable reduction in both visible bacteria and the associated biofilm. Mean tensile strength of catheters exposed to CLS was not significantly different compared to controls (P>0.05).

CONCLUSIONS

These in-vitro results suggest that NACLEV-CLS can significantly reduce all bacterial colonization and potentially help salvage infected catheters without affecting the catheter's mechanical integrity.

SIGNIFICANCE AND IMPACT OF STUDY

This study presents a novel CLS with a broad spectrum of antimicrobial activity against catheter-associated infections, particularly in long-term catheters.

Can dalbavancin be used as a catheter lock solution?

Purpose. The new lipoglycopeptide dalbavancin has only been approved for acute bacterial skin and skin structure infections. However, its alternative use as a catheter lock solution could facilitate the conservative management of catheter-related bloodstream infection. Our objective was to assess the stability and activity of dalbavancin alone and in combination with heparin against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) biofilms. We also compared the results with those obtained with vancomycin alone and in combination with heparin.Methodology. We used a 96-well plate in vitro model based on 24 h biofilms of MRSA and MRSE (ATCC 43300, ATCC 35984 and one clinical strain of each). The biofilms were exposed to dalbavancin (0.128 mg ml^-1) and vancomycin (5 mg ml^-1) alone and in combination with heparin (60 IU). The median percentage reductions in metabolic activity, biomass, bacterial load, and cell viability for each solution were compared.Results. Dalbavancin combined with heparin significantly reduced the median [interquartile range (IQR)] percentage of metabolic activity in MRSA biofilms compared with vancomycin [90.0 % (70.4-92.9 %) versus 35.0 % (14.8-59.6 %), P=0.006]. For the remaining variables studied, the combination was not inferior to vancomycin for MRSA and MRSE.Conclusions. Dalbavancin proved to be active against MRSA and MRSE biofilms. The combination of dalbavancin with heparin is a promising catheter lock solution that has the advantage of locking the catheter at home for 7 days.

Comparison of linezolid and vancomycin lock solutions with and without heparin against biofilm-producing bacteria

PURPOSE

The activity of linezolid and vancomycin lock solutions against biofilm-producing strains of Staphylococcus aureus, S. epidermidis, and Enterococcus faecalis was studied.

METHODS

Two strains each of methicillin-susceptible S. aureus (MSSA), methicillin-resistant S. aureus (MRSA), and S. epidermidis, and 1 strain of vancomycin-susceptible E. faecalis and vancomycin-resistant E. faecalis were tested against vancomycin and linezolid to assess prevention of biofilm formation and eradication of these pathogens within a formed biofilm. Activity was also tested in a 72-hour in vitro central venous catheter (CVC) model. After 24 hours of biofilm growth in a CVC, a lock solution containing vancomycin (2 or 5 mg/mL) or linezolid (1 or 2 mg/mL) alone or in combination with heparin sodium (5,000 units/mL with benzyl alcohol 0.45%) was instilled and incubated at 35 °C for 72 hr. Heparin and 0.9% sodium chloride injection were also tested.

RESULTS

Linezolid and vancomycin prevented biofilm formation below the minimum inhibitory concentration for 88% and 25% of isolates tested, respectively. The addition of preservative-containing heparin decreased the activity of vancomycin and linezolid lock solutions against all strains. Vancomycin 2- and 5-mg/mL lock solutions had the most activity against MSSA and E. faecalis strains (p < 0.01). Linezolid 2 mg/mL was the most active lock solution against the MRSA strains tested (p < 0.01). There were no significant differences in vancomycin or linezolid lock solution activity against S. epidermidis.

CONCLUSION

Heparin reduced activity of vancomycin and linezolid lock solutions against S. aureus, S. epidermidis, and E. faecalis biofilms. While linezolid or vancomycin lock solution reduced overall biofilm burden, it did not completely eradicate the bacteria at tested concentrations.

In Vitro Approach for Identification of the Most Effective Agents for Antimicrobial Lock Therapy in the Treatment of Intravascular Catheter-Related Infections Caused by Staphylococcus aureus

Infection of intravascular catheters by Staphylococcus aureus is a significant risk factor within the health care setting. To treat these infections and attempt salvage of an intravascular catheter, antimicrobial lock solutions (ALSs) are being increasingly used. However, the most effective ALSs against these biofilm-mediated infections have yet to be determined, and clinical practice varies greatly. The purpose of this study was to evaluate and compare the efficacies of antibiotics and antiseptics in current clinical use against biofilms produced by reference and clinical isolates of S. aureus Static and flow biofilm assays were developed using newly described in vivo-relevant conditions to examine the effect of each agent on S. aureus within the biofilm matrix. The antibiotics daptomycin, tigecycline, and rifampin and the antiseptics ethanol and Taurolock inactivated established S. aureus biofilms, while other commonly used antistaphylococcal antibiotics and antiseptic agents were less effective. These findings were confirmed by live/dead staining of S. aureus biofilms formed and treated within a flow cell model. The results from this study demonstrate the most effective clinically used agents and their concentrations which should be used within an ALS to treat S. aureus-mediated intravascular catheter-related infections.

Daptomycin antibiotic lock therapy for hemodialysis patients with Gram-positive bloodstream infections following use of tunneled, cuffed hemodialysis catheters: retrospective single center analysis

Catheter-related blood stream infection (CRBSI) is a major complication in hemodialysis patients. We assessed the efficacy of systemic daptomycin (DPT) plus DPT antibiotic lock therapy (DPT-ALT) for catheter salvage in patients with Gram-positive CRBSIs. This is a retrospective study of hemodialysis patients with tunneled and cuffed hemodialysis catheters. All patients were from a single institution in Taipei and received systemic DPT plus DPT-ALT for the treatment of Gram-positive CRBSI. Successful resolution of CRBSI was implemented. Resolution of fever within 48 hours, negative result of repeated blood cultures after resolution of fever, no clinical evidence of CRBSI relapse and no need for catheter removal were measured. Fifteen hemodialysis patients received DPT-ALT for CRBSI, nine with coagulase-negative Staphylococcus (CONS), two with methicillin-resistant Staphylococcus aureus (MRSA), three with methicillin-sensitive Staphylococcus aureus (MSSA) and one with polymicrobial infections. Systemic DPT plus DPT-ALT cured 11 patients (73.3%). Treatment failed in all three MRSA cases (two with MRSA and one with MRSA + Enterococcus faecalis). Retrospective design and small sample size were the limitations of this study. Systemic DPT plus DPT-ALT appears to be a promising treatment for CRBSI from CONS and MSSA, but not for MRSA CRBSI. Systemic DPT plus DPT-ALT should be considered for patients with CRBSIs caused by certain species.

In vitro efficacy of daptomycin and teicoplanin combined with ethanol, clarithromycin or gentamicin as catheter lock solutions

Background

Despite widespread use, optimum choice of antimicrobial agents, concentrations, combinations and exposure times have not been determined for antibiotic lock technique (ALT). Our objective was to evaluate the efficacy of different antibiotic combinations using an in vitro model of catheter-related infection. Daptomycin (DAP) 5 mg/mL, teicoplanin (TEC) 5 mg/mL, both alone and combined with gentamicin (GM) 2.5 mg/mL, clarythromycin (CLA) 5 mg/mL or ethanol 35 % were evaluated against four clinical strains of methicillin resistant coagulase negative staphylococci. Lock solutions were renewed every 24 h.

Results

After 72 h catheters were reincubated with culture media to investigate bacterial regrowth. All antibiotic combinations resulted in significant reductions (p < 0.05) of Log(10) cfu/mL at 72 h for both organisms compared with controls. DAP resulted in significant reductions of Log(10) for all organism versus TEC (p = 0.001). Only DAP reached the limit of detection at 72 h, however did not prevent regrowth after 24 h of ALT removal. DAP + Ethanol and TEC + ethanol eradicated biofilm at 72 h, but only DAP + ethanol (against all strains) and DAP + CLA (against two strains) prevented regrowth at 24 h after ALT removal.

Conclusions

Based on these data, ALT with DAP + ethanol and DAP + CLA should be explored in clinical trials.

Searching for new strategies against polymicrobial biofilm infections: guanylated polymethacrylates kill mixed fungal/bacterial biofilms

OBJECTIVES

Biofilm-related human infections have high mortality rates due to drug resistance. Cohabitation of diverse microbes in polymicrobial biofilms is common and these infections present additional challenges for treatment compared with monomicrobial biofilms. Here, we address this therapeutic gap by assessing the potential of a new class of antimicrobial agents, guanylated polymethacrylates, in the treatment of polymicrobial biofilms built by two prominent human pathogens, the fungus Candida albicans and the bacterium Staphylococcus aureus.

METHODS

We used imaging and quantitative methods to test the antibiofilm efficacy of guanylated polymethacrylates, a new class of drugs that structurally mimic antimicrobial peptides. We further compared guanylated polymethacrylates with first-line antistaphylococcal and anti-Candida agents used as combinatorial therapy against polymicrobial biofilms.

RESULTS

Guanylated polymethacrylates were highly effective as a sole agent, killing both C. albicans and S. aureus when applied to established polymicrobial biofilms. Furthermore, they outperformed multiple combinations of current antimicrobial drugs, with one of the tested compounds killing 99.98% of S. aureus and 82.2% of C. albicans at a concentration of 128 mg/L. The extracellular biofilm matrix provided protection, increasing the MIC of the polymethacrylates by 2-4-fold when added to planktonic assays. Using the C. albicans bgl2ΔΔ mutant, we implicate matrix polysaccharide β-1,3 glucan in the mechanism of protection. Data for two structurally distinct polymers suggest that this mechanism could be minimized through chemical optimization of the polymer structure. Finally, we demonstrate that a potential application for these polymers is in antimicrobial lock therapy.

CONCLUSIONS

Guanylated polymethacrylates are a promising lead for the development of an effective monotherapy against C. albicans/S. aureus polymicrobial biofilms.

A controlled antibiotic release system to prevent orthopedic-implant associated infections: An in vitro study

A new device for local delivery of antibiotics is presented, with potential use as a drug-eluting fixation pin for orthopedic applications. The implant consists of a stainless steel hollow tubular reservoir packed with the desired antibiotic. Release takes place through several orifices previously drilled in the reservoir wall, a process that does not compromise the mechanical properties required for the implant. Depending on the antibiotic chosen and the number of orifices, the release profile can be tailored from a rapid release of the load (ca. 20 h) to a combination of rapid initial release and slower, sustained release for a longer period of time (ca. 200 h). An excellent bactericidal action is obtained, with 4-log reductions achieved in as little as 2 h, and total bacterial eradication in 8 h using 6-pinholed implants filled with cefazolin.

OTO-201: nonclinical assessment of a sustained-release ciprofloxacin hydrogel for the treatment of otitis media

HYPOTHESIS

OTO-201 can provide sustained release to the middle ear and effectively treat otitis media, when compared with FDA-approved ciprofloxacin otic drop formulations.

BACKGROUND

There is an unmet medical need for antibiotic therapy that can provide a full course of treatment from a single administration by an otolaryngologist at the time of tympanostomy tube placement, obviating the need for twice daily multiday treatment with short-acting otic drops.

METHODS

Studies in guinea pigs and chinchillas were conducted. OTO-201 was administered as a single intratympanic injection and compared with the twice daily multi-day treatment with Ciprodex or Cetraxal otic drops.

RESULTS

OTO-201 demonstrated sustained release of ciprofloxacin in the middle ear compartment for days to approximately 2 weeks depending on the dose. The substantial C(max) values and steady drug exposure yielded by OTO-201 were in contrast to the pulsatile short lasting exposure seen with Ciprodex and Cetraxal. OTO-201 was also effective in a preclinical chinchilla model of Streptococcus pneumoniae-induced otitis media. The degree of cure was comparable to that afforded by Ciprodex and Cetraxal. There was no evidence of middle or inner ear pathology in guinea pigs treated with OTO-201, unlike Ciprodex and Cetraxal, which both demonstrated mild cochlear ototoxicity. No adverse effects of the poloxamer 407 vehicle were noted.

CONCLUSION

Intratympanic injection of OTO-201 constitutes an attractive treatment option to twice daily multiday dosing with ciprofloxacin ear drops for the treatment of otitis media, as evidenced by superior middle ear drug exposure, efficacy in an acute otitis media model, safety of administration, and convenience of a single dose regimen.

Influence of sub-inhibitory antibiotics and flow condition on Staphylococcus aureus ATCC 6538 biofilm development and biofilm growth rate: BioTimer assay as a study model

Staphylococcus biofilm exhibits high antibiotic resistance and therapeutic doses of antibiotics are often sub-inhibitory. Whereas data are available on the effect of sub-inhibitory antibiotics on matrix formation, little is known on their influence on biofilm population. Here, using BioTimer Assay (BTA), a method developed to quantify biofilm population, the influence of sub-inhibitory gentamicin, ofloxacin and azithromycin on Staphylococcus aureus ATCC 6538 biofilm population in flow with respect to static condition was assessed. Antibiotics and flow condition increased biofilm population even if at different extent, depending on the antibiotic molecule. The greatest bacterial population was found in biofilm developed under flow condition in the presence of azithromycin. A significant increase in biofilm matrix was recorded for biofilm developed in the presence of antibiotics in flow with respect to static condition. The growth rates (GRs) of 24-h biofilm developed under the influence of antibiotics and flow condition were also evaluated using BTA and a specific mathematical model. Antibiotics and flow condition affected the GRs of 24-h biofilm even if at different extent. The lowest GR value was recorded for biofilm developed under flow condition in the presence of ofloxacin. Although further studies are needed, our data indicate that antibiotics and flow condition influenced biofilm development by increasing both bacterial population and matrix formation and affected the GRs of the developed biofilm. To the best of our knowledge, BTA is unique in allowing the calculation of the GRs of biofilm and it may be considered to be a useful study model to evaluate the activity of antibiofilm molecules.

Antimicrobial activity of tigecycline alone or in combination with rifampin against Staphylococcus epidermidis in biofilm

Staphylococcus epidermidis is a commensal inhabitant of the healthy human skin, but in the recent years, it has been recognized as a nosocomial pathogen especially in immunocompromised patients. The pathogenesis of S. epidermidis is thought to be based on its capacity to form biofilms on the surface of medical devices, where bacterial cells may persist, protected from host defence and antimicrobial agents. Rifampin has been shown to be one of the most active antimicrobial agents in the eradication of the staphylococcal biofilm. However, this antibiotic should not be used in monotherapy. Therefore, one of the objectives of our research was to study the efficacy of the tigecycline/rifampin combination against methicillin-resistant S. epidermidis embedded in biofilms. Of the 80 clinically significant S. epidermidis isolates, 75 strains possess the ability to form a biofilm. These bacteria formed the biofilm via ica-dependent mechanisms. However, other biofilm-associated genes, including aap (encoding accumulation-associated protein) and bhp (coding cell wall-associated protein), were present in 85 and 29 % of isolates, respectively. The biofilm structures of S. epidermidis strains were also analyzed in confocal laser scanning microscopy (CLSM) and the obtained image demonstrated differences in their architecture. In vitro studies showed that the MIC value for tigecycline against S. epidermidis growing in the biofilm ranged from 0.125 to 2 μg/mL. Tigecycline in combination with rifampin demonstrated higher activity against bacteria embedded in biofilms than tigecycline alone.

From in vitro to in vivo Models of Bacterial Biofilm-Related Infections

The influence of microorganisms growing as sessile communities in a large number of human infections has been extensively studied and recognized for 30–40 years, therefore warranting intense scientific and medical research. Nonetheless, mimicking the biofilm-life style of bacteria and biofilm-related infections has been an arduous task. Models used to study biofilms range from simple in vitro to complex in vivo models of tissues or device-related infections. These different models have progressively contributed to the current knowledge of biofilm physiology within the host context. While far from a complete understanding of the multiple elements controlling the dynamic interactions between the host and biofilms, we are nowadays witnessing the emergence of promising preventive or curative strategies to fight biofilm-related infections. This review undertakes a comprehensive analysis of the literature from a historic perspective commenting on the contribution of the different models and discussing future venues and new approaches that can be merged with more traditional techniques in order to model biofilm-infections and efficiently fight them.

Daptomycin and tigecycline have broader effective dose ranges than vancomycin as prophylaxis against a Staphylococcus aureus surgical implant infection in mice

Vancomycin is widely used for intravenous prophylaxis against surgical implant infections. However, it is unclear whether alternative antibiotics used to treat methicillin-resistant Staphylococcus aureus (MRSA) infections are effective as prophylactic agents. The aim of this study was to compare the efficacies of vancomycin, daptomycin, and tigecycline as prophylactic therapy against a methicillin-sensitive S. aureus (MSSA) or MRSA surgical implant infection in mice. MSSA or MRSA was inoculated into the knee joints of mice in the presence of a surgically placed medical-grade metallic implant. The efficacies of low- versus high-dose vancomycin (10 versus 110 mg/kg), daptomycin (1 versus 10 mg/kg), and tigecycline (1 versus 10 mg/kg) intravenous prophylaxis were compared using in vivo bioluminescence imaging, ex vivo bacterial counts, and biofilm formation. High-dose vancomycin, daptomycin, and tigecycline resulted in similar reductions in bacterial burden and biofilm formation. In contrast, low-dose daptomycin and tigecycline were more effective than low-dose vancomycin against the implant infection. In this mouse model of surgical implant MSSA or MRSA infection, daptomycin and tigecycline prophylaxis were effective over a broader dosage range than vancomycin. Future studies in humans will be required to determine whether these broader effective dose ranges for daptomycin and tigecycline in mice translate to improved efficacy in preventing surgical implant infections in clinical practice.

Successful tigecycline lock therapy in a Lactobacillus rhamnosus catheter-related bloodstream infection

INTRODUCTION

Catheter-related bloodstream infections very often involve the premature removal of long-term intravascular devices (LTID). The antibiotic lock therapy (ALT) represents a conservative approach to the treatment of uncomplicated infections of tunneled LTID when catheter removal is not a feasible option.

CASE REPORT

We present here the first reported case of tunneled LTID bloodstream infection due to a multidrug resistant Lactobacillus rhamnosus. The patient, who had large granular lymphocytic leukemia, was successfully treated with systemic tigecycline therapy and lock therapy.

CONCLUSION

Our results confirm ALT as a valid catheter-salvage strategy for the treatment of CRBSIs in clinically stable patients when catheter removal is not a feasible option, tigecycline appear to be a good option.

Biofilm elimination on intravascular catheters: important considerations for the infectious disease practitioner

The presence of biofilms on intravascular catheters and their role in catheter-related bloodstream infections is well accepted. The tolerance of catheter-associated biofilm organisms toward systemic antimicrobial treatments and the potential for development of antimicrobial resistance in the health care environment underscores the importance of alternative treatment strategies. Biofilms are microbial communities that exhibit unique characteristics that must be considered when evaluating the potential of biofilm prevention or control strategies. Because biofilm-associated infections do not respond consistently to therapeutically achievable concentrations of many antimicrobial agents, treatments that are more effective against slowly growing biofilm cells or combination treatments that can penetrate the biofilm matrix may be more effective. Alternative strategies that do not incorporate antimicrobial drugs have also been investigated. These approaches have the potential to prevent or eradicate biofilms on indwelling intravascular catheters and prevent or resolve catheter-related infections.

Hollow porous implants filled with mesoporous silica particles as a two-stage antibiotic-eluting device

A new type of implantable drug eluting device is presented, consisting of a bed of mesoporous microparticles packed inside a reservoir with a porous wall. This provides two sets of variables for drug release control that can be tailored independently. The first is related to the microparticles (packing density, size and pore structure) and the second to the reservoir (pore diameter and thickness of the wall, permeation area). In this work the concept is developed into a working model, used to fight bacterial (Staphylococcus aureus) growth by releasing linezolid that had previously been adsorbed on silica microparticles. These particles were placed inside the hollow interior of a porous medical grade stainless steel pin mimicking those used in traumatology and in orthopedic surgery. The mechanical behavior of the porous drug-eluting pin was tested and found satisfactory.

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

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

Immune defense of rats immunized with fennel honey, propolis, and bee venom against induced staphylococcal infection

The objective of this work was to evaluate the potency of bee product-immunized rats to overcome an induced Staphylococcus aureus infection. Forty rats were divided to eight groups: T1, T3, and T5 received, respectively, fennel honey, ethanol, and aqueous propolis extracts orally, and T2, T4, and T6 were administered the respective materials intraperitoneally; T7 received bee venom by the bee sting technique; and T8 was the control group. All groups were challenged by a bovine clinical mastitis isolate of S. aureus. Each rat received 2 mL of broth inoculated with 1 x 10(5) colony-forming units/mL intraperitoneally. Two weeks post-induced infection all rats were sacrificed and eviscerated for postmortem inspection and histopathological study. Three rats from T8 and one rat from T7 died before sacrifice. Another two rats, one each in T4 and T5, had morbidity manifestations. The remaining experimental animals showed apparently healthy conditions until time of sacrifice. Postmortem inspection revealed that all T8 rats showed different degrees of skeletal muscle and internal organ paleness with scattered focal pus nodules mainly on lungs and livers. All rats of the treated groups showed normal postmortem features except three rats. A dead rat in group T7 showed focal pus nodules on the lung surface only, whereas the affected two rats in groups T4 and T5 appeared normal except with some pus nodules, but much smaller than in the control, scattered on the hepatic surface and mesentery. Histopathological studies revealed that T8 rats had typical suppurative bronchopneumonia and or severe degenerative and necrobiotic changes in hepatic tissues. Three affected rats of the treated groups showed slight bronchopneumonia or degenerative hepatic changes only. The other animals of the treated groups showed completely normal parenchymatous organs with stimulated lymphatic tissues. It was concluded that all tested previously bee product-immunized rats could significantly challenge the induced S. aureus infection (P < .01). The effects were more pronounced in rats that had received fennel honey solution.

Automating a 96-well microtitre plate model for Staphylococcus aureus biofilms: an approach to screening of natural antimicrobial compounds

The purpose of this study was to establish and automate an assay to be used for screening novel antimicrobial agents against biofilm-forming Staphylococcus aureus bacteria. The selected assay was based on crystal violet staining, which is a well used method for staining bacterial biofilms. The method was first optimised manually, antibiotic susceptibility was established and biofilm formation in plates was confirmed using atomic force microscopy. Automation of the assay was done using a Thermo Scientific Multidrop((R)) Combi dispenser and Biomek((R)) 3000 liquid handling workstation. A detailed comparison of the performance between the manual and the automated method was made in terms of screening window coefficient as well as other statistical parameters and repeatability measurements, such as plate-to-plate and day-to-day variability. Automated screening of an in-house library of natural products gave the same positive hits as previously reported, therefore the developed assay can be regarded as a reliable screening tool.

Empiric therapy for intravenous central line infections and nosocomially-acquired acute bacterial endocarditis

Intravascular catheters are essential devices in the intensive care unit, yet catheter-related bloodstream infections (CR-BSI) are associated with increased morbidity and mortality, prolonged hospitalization, and increased medical costs. Management of a CR-BSI requires antibiotics, with or without catheter removal, depending on patient and etiologic factors. Because of the high frequency of staphylococcal infections, it is wise to use a glycopeptide empirically. Extra coverage for Gram-negative bacilli should be administered in severely ill or immunocompromised patients. Once culture and sensitivity results are known, antibiotic therapy can be more selective.

Bacterial and fungal biofilm infections

Biofilms are communal structures of microorganisms encased in an exopolymeric coat that form on both natural and abiotic surfaces and have been associated with a variety of persistent infections that respond poorly to conventional antibiotic chemotherapy. Biofilm infections of certain indwelling medical devices by common pathogens such as staphylococci are not only associated with increased morbidity and mortality but are also significant contributors to the emergence and dissemination of antibiotic resistance traits in the nosocomial setting. Current treatment paradigms for biofilm-associated infections of semipermanent indwelling devices typically involve surgical replacement of the device combined with long-term antibiotic therapy and incur high health care costs. This review summarizes the existing data relating to the nature, prevalence, and treatment of biofilm-associated infections and highlights experimental approaches and therapies that are being pursued toward more effective treatments.

Pretreatment with the protegrin IB-367 affects Gram-positive biofilm and enhances the therapeutic efficacy of linezolid in animal models of central venous catheter infection

BACKGROUND

Biofilms play an important role in the pathogenesis of several chronic infections and nosocomial infections related to indwelling medical devices.

METHODS

To assess the efficacy of IB-367 and linezolid (LZD) in the treatment of central venous catheter (CVC) infections using the antibiotic-lock technique, in vitro and in vivo studies were performed. The in vitro antibiotic susceptibility assay for Staphylococcus aureus and Enterococcus faecalis biofilms developed on 96-well polystyrene tissue culture plates was performed to determine the activity of the compounds. Efficacy studies were performed in rat models of Gram-positive CVC infection. Silastic catheters were implanted into the superior cava of adult male Wistar rats. Twenty-four hours after implantation, the catheters were pretreated by filling with IB-367. Thirty minutes later, rats were challenged via the CVC with 1.0 x 10(6) CFU (colony forming units) of S aureus strain diffuse Smith and clinical isolate of slime-producing E faecalis. Administration of LZD into the CVC at a concentration equal to the minimum bacteriocidal concentration observed using adherent cells or at a much higher concentration (1024 microg/mL) began 24 hours later.

RESULTS

Both for S aureus and E faecalis, the killing activities of LZD against adherent bacteria were at least 4-fold to 8-fold lower than that against freely growing cells. For both strains, in IB-367-pretreated wells, LZD strongly increases its activity. The in vivo studies showed that when CVCs were pretreated with IB-367, Gram-positive biofilm bacterial load was further decreased to 10(1) CFU/mL and bacteremia was not detected.

CONCLUSIONS

IB-367 has potential as an adjunctive agent to LZD in the treatment of Gram-positive biofilm infections such as CVC infections.

Guidelines on the insertion and management of central venous access devices in adults

Central venous access devices are used in many branched of medicine where venous access is required for either long-term or a short-term care. These guidelines review the types of access devices available and make a number of major recommendations. Their respective advantages and disadvantages in various clinical settings are outlined. Patient care prior to, and immediately following insertion is discussed in the context of possible complications and how these are best avoided. There is a section addressing long-term care of in-dwelling devices. Techniques of insertion and removal are reviewed and management of the problems which are most likely to occur following insertion including infection, misplacement and thrombosis are discussed. Care of patients with coagulopathies is addressed and there is a section addressing catheter-related problems.

Outcome of totally implantable venous access device-related bacteraemia without device removal

The optimal management of bacteraemia related to the presence of totally implantable venous access devices (TIVADs) remains controversial, particularly in terms of whether to remove the infected catheter. The objective of this study was to determine the factors associated with success or failure of treatment of TIVAD-related bacteraemia in patients from whom the infected device was not removed. The outcome of 92 episodes of TIVAD-related bacteraemia and the factors predictive of an unfavourable outcome were evaluated retrospectively. In 32 (35%) episodes, the devices were removed immediately. In 60 episodes, patients were treated with antibiotics infused through the device; treatment was successful in 56% of these cases (66% for infections caused by coagulase-negative staphylococci). Only the presence of sepsis (OR 9.42, 95% CI 1.29-68.92, p 0.0271) and of local signs of infection (OR 9.61, 95% CI 1.98-46.49, p 0.0049) independently predicted the failure of catheter-retaining treatment. Finally, only one-third of the devices were retained. In conclusion, the large number of TIVADs that are removed because of infection justifies reconsidering the criteria for device removal. During catheter-retaining treatment, the presence of local signs of infection or reported sepsis were independent factors for reduced probability of retaining the device.

Pharmacodynamics of antibiotics to treat multidrug-resistant Gram-positive hospital infections

Hospital infection due to multidrug-resistant Gram-positive bacteria may often represent a life-threatening challenge; thus, to appropriately combat them, clinicians should be confident and systematically apply several important pharmacodynamic concepts. The concept of 'correct antibiotic treatment' should include, in addition to an appropriate choice in terms of antimicrobial susceptibility, an appropriate dosage and administration schedule consistent with the pharmacodynamic principles. In the next few years, it is expected that some of the anti-Gram-positive antimicrobial agents that are currently under investigation will be added to the therapeutic armamentarium. However, optimization of the usage of old drugs still remains a clinical priority and a scientific challenge, whose dignity may be considered of similar importance to that of the assessment of the possible therapeutic role of the new compounds.

Distinctin improves the efficacies of glycopeptides and betalactams against staphylococcal biofilm in an experimental model of central venous catheter infection

The ability of microorganisms to adhere to medical implants is a problem of high visibility and has been focused in numerous investigations. To assess the efficacy of distinctin and conventional antibiotics in the treatment of central venous catheter in vitro and in vivo studies were performed. The in vitro susceptibility assay was performed against S. aureus biofilms developed on 96-well polystyrene tissue culture plates. Efficacy studies were performed in a rat model of CVC infection. Twenty-four hours after implantation, the catheters were filled with distinctin. Thirty minutes later, rats were challenged via the CVC with S. aureus. Administration of antibiotics into the CVC at a concentration equal to the MBC for adherent cells, or at 1024 microg/mL began 24 h later. The killing activities of all antibiotics against adherent bacteria were at least four- to eightfold lower than against freely growing cells. When antibiotics were used in distinctin pretreated wells, they showed a significant increase of activity. The in vivo studies showed that when CVCs were pretreated with distinctin biofilm bacterial load was further decreased to 10(1) CFU/mL and bacteremia was not detected. Distinctin displays potential as an adjunctive agent to antibiotics in the treatment of CVC-related infections.

Colony spreading in Staphylococcus aureus

Wild-type Staphylococcus aureus rapidly expands on the surface of soft agar plates. The rates of expansion and the shapes of the resultant giant colonies were distinct for different strains of laboratory stocks and clinical isolates. The colony spreading abilities did not correlate with the biofilm-forming abilities in these strains. Insertional disruption of the dltABCD operon, which functions at the step of D-alanine addition to teichoic acids, and of the tagO gene, which is responsible for the synthesis of wall teichoic acids, decreased the colony spreading ability. The results indicate that wall teichoic acids and D-alanylation of teichoic acids are required for colony spreading.