Lack of antimicrobial activity of sodium heparin for treating experimental catheter-related infection due to Staphylococcus aureus using the antibiotic-lock technique

ESPEN guideline on chronic intestinal failure in adults - Update 2023

BACKGROUND & AIMS

In 2016, ESPEN published the guideline for Chronic Intestinal Failure (CIF) in adults. An updated version of ESPEN guidelines on CIF due to benign disease in adults was devised in order to incorporate new evidence since the publication of the previous ESPEN guidelines.

METHODS

The grading system of the Scottish Intercollegiate Guidelines Network (SIGN) was used to grade the literature. Recommendations were graded according to the levels of evidence available as A (strong), B (conditional), 0 (weak) and Good practice points (GPP). The recommendations of the 2016 guideline (graded using the GRADE system) which were still valid, because no studies supporting an update were retrieved, were reworded and re-graded accordingly.

RESULTS

The recommendations of the 2016 guideline were reviewed, particularly focusing on definitions, and new chapters were included to devise recommendations on IF centers, chronic enterocutaneous fistulas, costs of IF, caring for CIF patients during pregnancy, transition of patients from pediatric to adult centers. The new guideline consist of 149 recommendations and 16 statements which were voted for consensus by ESPEN members, online in July 2022 and at conference during the annual Congress in September 2022. The Grade of recommendation is GPP for 96 (64.4%) of the recommendations, 0 for 29 (19.5%), B for 19 (12.7%), and A for only five (3.4%). The grade of consensus is "strong consensus" for 148 (99.3%) and "consensus" for one (0.7%) recommendation. The grade of consensus for the statements is "strong consensus" for 14 (87.5%) and "consensus" for two (12.5%).

CONCLUSIONS

It is confirmed that CIF management requires complex technologies, multidisciplinary and multiprofessional activity, and expertise to care for the underlying gastrointestinal disease and to provide HPN support. Most of the recommendations were graded as GPP, but almost all received a strong consensus.

Culture-directed antibiotics in peritoneal dialysis solutions: a systematic review focused on stability and compatibility

BACKGROUND

This systematic review summarises the stability of less commonly prescribed antibiotics in different peritoneal dialysis solutions that could be used for culture-directed therapy of peritonitis, which would be especially useful in regions with a high prevalence of multidrug antibiotic-resistant strains.

METHODS

A literature search of Medline, Scopus, Embase and Google Scholar for articles published from inception to 25 January, 2023 was conducted. Only antibiotic stability studies conducted in vitro and not recently reviewed by So et al. were included. The main outcomes were chemical, physical, antimicrobial and microbial stability. This protocol was registered in PROSPERO (registration number CRD42023393366).

RESULTS

We screened 1254 abstracts, and 28 articles were included in the study. In addition to those discussed in a recent systematic review (So et al., Clin Kidney J 15(6):1071-1078, 2022), we identified 18 antimicrobial agents. Of these, 9 have intraperitoneal dosing recommendations in the recent International Society for Peritoneal Dialysis (ISPD) peritonitis guidelines, and 7 of the 9 had stability data applicable to clinical practice. They were cefotaxime, ceftriaxone, daptomycin, ofloxacin, and teicoplanin in glucose-based solutions, tobramycin in Extraneal solution only and fosfomycin in Extraneal, Nutrineal, Physioneal 1.36% and 2.27% glucose solutions.

CONCLUSIONS

Physicochemical stability has not been demonstrated for all antibiotics with intraperitoneal dosing recommendations in the ISPD peritonitis guidelines. Further studies are required to determine the stability of antibiotics, especially in icodextrin-based and low-glucose degradation products, pH-neutral solutions.

Urokinase-based lock solutions for catheter salvage: A case of an upcoming kidney transplant recipient

Catheter-related bloodstream infection (CRBSI) is a significant complication among patients on haemodialysis (HD) who are dependent on a central venous catheter (CVC) for an extended period. Catheter removal as first-line treatment can induce accelerated venous access site depletion in patients on HD who rely on it to survive. It is possible to retain the catheter in stable patients without septic syndrome while administering systemic antibiotics and antibiotic lock therapy. Herein, we report the case of a patient on HD with CRBSI who was successfully treated with intravenous levofloxacin- and urokinase-based antibiotic lock, without catheter removal prior to kidney transplantation. The use of urokinase in combination with antibiotics in lock solutions for treating catheter infections is rare. We verified the physical compatibility of levofloxacin and urokinase by visual inspection, turbidimetric measurements, and particle count. To our knowledge, this was a rare case demonstrating the effective use of urokinase and levofloxacin in a catheter lock for CRBSI in a patient on HD. Considering the need for highly concentrated antimicrobials and the availability of various antibiotics, the compatibility and stability of the lock solution is a matter of concern. Further studies are warranted to assess the stability and compatibility of various antibiotics in combination with urokinase.

Antifungal and Cytotoxic Evaluation of Photochemically Synthesized Heparin-Coated Gold and Silver Nanoparticles

Heparin-based silver nanoparticles (AgHep-NPs) and gold nanoparticles (AuHep-NPs) were produced by a photochemical method using silver nitrate and chloroauric acid as metal precursors and UV light at 254 nm. UV-Vis spectroscopy graphs showed absorption for AgHep-NPs and AuHep-NPs at 420 nm and 530 nm, respectively. TEM revealed a pseudospherical morphology and a small size, corresponding to 10-25 nm for AgHep-NPs and 1.5-7.5 nm for AuHep-NPs. Their antifungal activity against Candida albicans, Issatchenkia orientalis (Candida krusei), and Candida parapsilosis was assessed by the microdilution method. We show that AgHep-NPs were effective in decreasing fungus density, whereas AuHep-NPs were not. Additionally, the viability of human gingival fibroblasts was preserved by both nanoparticle types at a level above 80%, indicating a slight cytotoxicity. These results are potentially useful for applications of the described NPs mainly in dentistry and, to a lesser extent, in other biomedical areas.

Blood Compatibility-An Important but Often Forgotten Aspect of the Characterization of Antimicrobial Peptides for Clinical Application

Acylation of antimicrobial peptides mimics the structure of the natural lipopeptide polymyxin B, and increases antimicrobial and endotoxin-neutralizing activities. In this study, the antimicrobial properties of lactoferrin-based LF11 peptides as well as blood compatibility as a function of acyl chain length were investigated. Beyond the classical hemolysis test, the biocompatibility was determined with human leukocytes and platelets, and the influence of antimicrobial peptides (AMPs) on the plasmatic coagulation and the complement system was investigated. The results of this study show that the acylation of cationic peptides significantly reduces blood tolerance. With increasing acyl chain length, the cytotoxicity of LF11 peptides to human blood cells also increased. This study also shows that acylated cationic antimicrobial peptides are inactivated by the presence of heparin. In addition, it could be shown that the immobilization of LF11 peptides leads to a loss of their antimicrobial properties.

ESPEN guidelines on chronic intestinal failure in adults

BACKGROUND & AIMS

Chronic Intestinal Failure (CIF) is the long-lasting reduction of gut function, below the minimum necessary for the absorption of macronutrients and/or water and electrolytes, such that intravenous supplementation is required to maintain health and/or growth. CIF is the rarest organ failure. Home parenteral nutrition (HPN) is the primary treatment for CIF. No guidelines (GLs) have been developed that address the global management of CIF. These GLs have been devised to generate comprehensive recommendations for safe and effective management of adult patients with CIF.

METHODS

The GLs were developed by the Home Artificial Nutrition & Chronic Intestinal Failure Special Interest Group of ESPEN. The GRADE system was used for assigning strength of evidence. Recommendations were discussed, submitted to Delphi rounds, and accepted in an online survey of ESPEN members.

RESULTS

The following topics were addressed: management of HPN; parenteral nutrition formulation; intestinal rehabilitation, medical therapies, and non-transplant surgery, for short bowel syndrome, chronic intestinal pseudo-obstruction, and radiation enteritis; intestinal transplantation; prevention/treatment of CVC-related infection, CVC-related occlusion/thrombosis; intestinal failure-associated liver disease, gallbladder sludge and stones, renal failure and metabolic bone disease. Literature search provided 623 full papers. Only 12% were controlled studies or meta-analyses. A total of 112 recommendations are given: grade of evidence, very low for 51%, low for 39%, moderate for 8%, and high for 2%; strength of recommendation: strong for 63%, weak for 37%.

CONCLUSIONS

CIF management requires complex technologies, multidisciplinary and multiprofessional activity, and expertise to care for both the underlying gastrointestinal disease and to provide HPN support. The rarity of the condition impairs the development of RCTs. As a consequence, most of the recommendations have a low or very low grade of evidence. However, two-thirds of the recommendations are considered strong. Specialized management and organization underpin these recommendations.

Viability of Selected Microorganisms in Non-Cytotoxic Aseptic Preparations

: Numerous ready-to-use parenteral solutions are aseptically prepared in pharmacy-based aseptic preparation units. Microbiological stability of the preparations is influenced by the cleanroom environment, the complexity of the aseptic process, conditions during administration and the microbiological vulnerability of the products.

: The aim of the study was to evaluate the ability of four different pathogens related to hospital infections to grow in ready-to-use, non-cytotoxic parenteral products aseptically prepared in hospital pharmacies.

: In four consecutive series the antimicrobial activity of the following products was tested: caspofungin 35 mg or 70 mg in 250 mL 0.9 % NaCl solution (NS), micafungin 0.5 mg/mL in NS, vancomycin 5 mg/mL in G5/G10, heparin-sodium 1 IE/mL in NS, epinephrine 0.02 mg/mL in G5, norepinephrine 0.01 mg/mL in G5, phenylephrine 0.1 mg/mL, KCl solution 0.8 mmol/mL, trace elements 1:1 in G5/G10, midazolam 1 mg/mL injection solution, tranexamic acid 100 mg/mL injection solution, 50 % glucose solution, SMOFlipid 20 % lipid emulsion, 1 % propofol injection.

Nine milliliter aliquots of each test solution were inoculated with 1 mL suspension of selected strains, i. e.

: Most of the tested preparations induced no growth inhibition of the tested organisms. The selected strains lost viability in preparations containing vancomycin, phenylephrine or midazolam after a period of a few hours or days. Glucose 50 % w/v solution generated antimicrobial activity against

: The lack of antimicrobial properties of ready-to-use, non-cytotoxic solutions should be considered while determining the shelf-life of the products. Ready-to-use preparations should be kept refrigerated whenever possible to inhibit the multiplication of any contaminating organism.

Anticoagulant properties of enoxaparin 400 IU/mL-40 % ethanol catheter lock solution

Unfractionated heparin (UFH) is the most widely used interdialytic lock solution but has no anti-infectious properties. Ethanol at a content ≥40 %v/v eradicates experimental biofilm but has no anticoagulant properties. In contrast to UFH, enoxaparin (Enox) can be combined with 40 % ethanol without precipitation. Enoxaparin 400 UI/mL–40 % ethanol (Enox/Eth) has antibiofilm properties and therefore has promise as an alternative lock solution. This study assessed the anticoagulant properties of Enox/Eth. Enox and Enox/Eth were diluted in whole blood at a final Enox concentration of 0.5, 1 (N = 6 samples), 1.5 (N = 4) and 2 (N = 6) IU/mL. Anti-Xa activity was determined by chromogenic assay and the inhibition of endogenous thrombin potential (ETP) by thrombinography. Quantitative data were compared by the Mann-Withney U test. For Enox concentrations of 0.5, 1, 1.5 and 2 UI/mL in whole blood samples, the mean ± SD values of the anti-Xa activity were 0.68 ± 0.09, 1.26 ± 0.14, 1.73 ± 0.30, 2.35 ± 0.32 UI/mL for Enox/Eth and 0.94 ± 0.15, 1.80 ± 0.22, 2.74 ± 0.23, 3.54 ± 0.44 UI/mL for Enox (P = 0.03, P = 0.03, P = 0.13, P = 0.03); and of the percentage of ETP inhibition was 17.36 ± 9.65, 30.27 ± 17.06, 36.5 ± 17.06, 57.82 ± 15.42 for Enox/Eth, and 42.96 ± 15.68, 68.93 ± 10.01, 83.5 ± 8.81, 91.19 ± 4.67 for Enox (P = 0.03, P = 0.03, P = 0.13, P = 0.03), respectively. The median and IQR values of Enox concentration inhibiting 50 % of ETP (IC50 ETP) were 1.8 [1.1–2.4] IU/mL for Enox/Eth and 0.7 [0.3–0.9] IU/mL for Enox, P = 0.03. Enox/Eth has strong anticoagulant activity, albeit lower than that of Enox, but with an extremely low IC50 ETP compared to the Enox concentration of non-diluted Enox/Eth.

Antibiotic lock therapy: review of technique and logistical challenges

Antibiotic lock therapy (ALT) for the prevention and treatment of catheter-related bloodstream infections is a simple strategy in theory, yet its real-world application may be delayed or avoided due to technical questions and/or logistical challenges. This review focuses on these latter aspects of ALT, including preparation information for a variety of antibiotic lock solutions (ie, aminoglycosides, beta-lactams, fluoroquinolones, folate antagonists, glycopeptides, glycylcyclines, lipopeptides, oxazolidinones, polymyxins, and tetracyclines) and common clinical issues surrounding ALT administration. Detailed data regarding concentrations, additives, stability/compatibility, and dwell times are summarized. Logistical challenges such as lock preparation procedures, use of additives (eg, heparin, citrate, or ethylenediaminetetraacetic acid), timing of initiation and therapy duration, optimal dwell time and catheter accessibility, and risks of ALT are also described. Development of local protocols is recommended in order to avoid these potential barriers and encourage utilization of ALT where appropriate.

Bacteriophage K antimicrobial-lock technique for treatment of Staphylococcus aureus central venous catheter-related infection: a leporine model efficacy analysis

PURPOSE

To determine whether a bacteriophage antimicrobial-lock technique can reduce bacterial colonization and biofilm formation on indwelling central venous catheters in a rabbit model.

MATERIALS AND METHODS

Cuffed central venous catheters were inserted into the jugular vein of female New Zealand White rabbits under image guidance. Catheters were inoculated for 24 hours with broth culture of methicillin-sensitive Staphylococcus aureus. The inoculum was aspirated, and rabbits were randomly assigned to two equal groups for 24 hours: (i) untreated controls (heparinized saline lock), (ii) bacteriophage antimicrobial-lock (staphylococcal bacteriophage K, propagated titer > 10(8)/mL). Blood cultures were obtained via peripheral veins, and the catheters were removed for quantitative culture and scanning electron microscopy.

RESULTS

Mean colony-forming units (CFU) per cm(2) of the distal catheter segment, as a measure of biofilm, were significantly decreased in experimental animals compared with controls (control, 1.2 × 10(5) CFU/cm(2); experimental, 7.6 × 10(3); P = .016). Scanning electron microscopy demonstrated that biofilms were present on the surface of five of five control catheters but only one of five treated catheters (P = .048). Blood culture results were not significantly different between the groups.

CONCLUSIONS

In a rabbit model, treatment of infected central venous catheters with a bacteriophage antimicrobial-lock technique significantly reduced bacterial colonization and biofilm presence. Our data represent a preliminary step toward use of bacteriophage therapy for prevention and treatment of central venous catheter-associated infection.

Stability and compatibility of antimicrobial lock solutions

PURPOSE

Published stability and compatibility data on a growing array of solutions used for antimicrobial lock therapy (ALT) are reviewed.

SUMMARY

ALT involves the instillation of a highly concentrated antimicrobial, often in combination with an anticoagulant, into a central venous catheter (CVC) lumen; this technique is often used for prophylaxis after CVC insertion or as an adjunctive treatment in cases of central line-associated bloodstream infection (CLABSI) if catheter removal is not feasible. Optimal selection of stable and compatible antimicrobials and additives can maximize catheter dwell times, streamline pharmacy compounding practices, and help ensure patient safety. Of 98 articles on ALT solutions identified in a literature search, 17 met the prespecified criteria for the use of validated stability and compatibility methodology. Antimicrobials active against common CLABSI pathogens that may be appropriate for ALT include cefazolin, cefotaxime, ceftazidime, ciprofloxacin, daptomycin, gentamicin, linezolid, telavancin, ticarcillin-clavulanic acid, and vancomycin; validated data demonstrate the stability of these agents in solution with heparin or nonheparin anticoagulants over 72-96 hours or longer. Other antifungal agents and antiinfectives (e.g., ethyl alcohol) have been used in specific patients and ALT situations. The prolonged stability of several antimicrobial-additive combinations may allow for extended dwell times and less frequent lock solution exchanges.

CONCLUSION

Pharmacists' knowledge of diverse combinations of antimicrobial agents and additives in lock solutions, including several shown to be stable and compatible for extended periods, can help expand and optimize the use of ALT in both treatment and prophylactic modalities.

Bacteriophage K for reduction of Staphylococcus aureusbiofilm on central venous catheter material

The purpose of this project was to determine whether bacteriophage can reduce bacterial colonization and biofilm formation on central venous catheter material. Twenty silicone discs were inoculated for 24 h with broth culture of Methicillin sensitive staphylococcus aureus (0.5 McFarland standard). The inoculate was aspirated and discs placed into two equal groups for 24 h: (1) untreated controls; (2) bacteriophage treatment (staphylococcal bacteriophage K, propagated titer > 10⁸). At the completion of the experiment discs were processed for quantitative culture. Statistical testing was performed using the rank sum test. Mean colony forming units (CFU) were significantly decreased in experimental compared with controls (control 6.3 × 10⁵ CFU, experimental 6.7 × 10¹, P ≤ 0.0001). Application of bacteriophage to biofilm infected central venous catheter material significantly reduced bacterial colonization and biofilm presence. Our data suggests that bacteriophage treatment may be a feasible strategy for addressing central venous catheter staph aureus biofilm infections.

Comparing normal saline versus diluted heparin to lock non-valved totally implantable venous access devices in cancer patients: a randomised, non-inferiority, open trial

BACKGROUND

Heparin has been used for years as a locking solution in totally implantable venous access devices. Normal saline (NS) might be a safe alternative for heparin. However, evidence of non-inferiority of NS versus heparin is lacking.

PATIENTS AND METHODS

We randomly allocated 802 cancer patients with a newly inserted port either to heparin lock (300 U/3 ml) or to NS lock groups in a 1:1 assignment ratio. The primary outcome was the number of functional complications, which was defined as 'easy injection, impossible aspiration' at port access. Secondary outcomes included all functional problems and catheter-related bacteraemia. We hypothesised that NS locks do not cause more functional problems and catheter-related bacteraemia than heparin locks. Non-inferiority is established if the upper limit of the confidence interval (CI) for the relative risk of NS versus heparin is <1.4.

RESULTS

Three hundred and eighty-two patients from the NS group and 383 from the heparin lock group were included in the analysis. The incidence rate of our primary outcome (easy injection, impossible aspiration) was 3.70% (95% CI 2.91%-4.69%) and 3.92% (95% CI 3.09%-4.96%) of accesses in the NS and heparin groups, respectively. The relative risk was 0.94% (95% CI 0.67%-1.32%). Catheter-related bloodstream infection was 0.03 per 1000 catheter days in the NS group and 0.10 per 1000 catheter days in the heparin group.

CONCLUSION

NS is a safe and effective locking solution in implantable ports if combined with a strict protocol for device insertion and maintenance.

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.

In vitro effectiveness of colistin, tigecycline and levofloxacin alone and combined with clarithromycin and/or heparin as lock solutions against embedded Acinetobacter baumannii strains

OBJECTIVES

To determine the in vitro stability and efficacy of colistin, tigecycline and levofloxacin alone or in combination with clarithromycin and/or heparin as lock solutions against biofilm-embedded Acinetobacter baumannii strains.

METHODS

Candidate antibiotics (colistin, tigecycline and levofloxacin) were investigated in vitro, either alone or in combination with clarithromycin and/or heparin in solution. The efficacy of antibiotic lock solutions was tested in an in vitro catheter biofilm model against A. baumannii isolated from catheter-related bacteraemia.

RESULTS

Candidate antibiotics at 400× MICs combined with clarithromycin (200 mg/mL) and/or heparin (1000 U/mL) were compatible. Colistin, tigecycline and levofloxacin and their combinations with clarithromycin demonstrated bactericidal activity against the biofilm-embedded A. baumannii strains. Compared with other antibiotics alone, the lock solution including only colistin was the best agent to eradicate A. baumannii embedded in the catheter model. When tested antibiotics were used in combination with clarithromycin, the combinations were significantly more effective and more rapid in reducing the live cell number or eliminating A. baumannii colonization in biofilms than each of the antibiotics alone.

CONCLUSIONS

Catheter lock solutions containing colistin may have the most promise for treating or preventing biofilm-producing catheter infections caused by A. baumannii. Clarithromycin was ultimately effective with the studied antibiotics to reduce live cell number or eradicate A. baumannii colonization in biofilms and could serve as an antibiotic enhancer. Our in vitro model findings now warrant clinical trials to investigate their real role in the management of catheter-related bacteraemia.

How to deal with dialysis catheters in the ICU setting

Acute kidney insufficiency (AKI) occurs frequently in intensive care units (ICU). In the management of vascular access for renal replacement therapy (RRT), several factors need to be taken into consideration to achieve an optimal RRT dose and to limit complications. In the medium and long term, some individuals may become chronic dialysis patients and so preserving the vascular network is of major importance. Few studies have focused on the use of dialysis catheters (DC) in ICUs, and clinical practice is driven by the knowledge and management of long-term dialysis catheter in chronic dialysis patients and of central venous catheter in ICU patients. This review describes the appropriate use and management of DCs required to obtain an accurate RRT dose and to reduce mechanical and infectious complications in the ICU setting. To deliver the best RRT dose, the length and diameter of the catheter need to be sufficient. In patients on intermittent hemodialysis, the right internal jugular insertion is associated with a higher delivered dialysis dose if the prescribed extracorporeal blood flow is higher than 200 ml/min. To prevent DC colonization, the physician has to be vigilant for the jugular position when BMI < 24 and the femoral position when BMI > 28. Subclavian sites should be excluded. Ultrasound guidance should be used especially in jugular sites. Antibiotic-impregnated dialysis catheters and antibiotic locks are not recommended in routine practice. The efficacy of ethanol and citrate locks has yet to be demonstrated. Hygiene procedures must be respected during DC insertion and manipulation.

Randomized study of minocycline and edetic acid as a locking solution for central line (port-a-cath) in children with cancer

BACKGROUND

Contamination of central catheters is frequent, and biofilm perpetuates infections. Heparin does not protect against infections because it has no antibiotic action. Minocycline and edetic acid (M-EDTA), a potent calcium chelating agent that destroys bacterial and fungal cell membrane and disrupts biofilm, may be an alternative to allow the associated antibiotic to act locally at a high and safe concentration.

METHODS

Fifty children with cancer and a port-a-cath were followed up: 26 received heparin (group 1) and 24 M-EDTA (group 2). A total of 762 serial prospective blood cultures were obtained, 387 from group 1 and 375 from group 2.

RESULTS

In group 1 (heparin), 19 blood cultures were positive, and infection incidence was 73.1% (19/26 ports). In group 2 (M-EDTA), 5 blood cultures were positive, and the incidence rate was 20.8% (5/24 ports).

CONCLUSION

M-EDTA, compared with heparin, prevents and treats catheter infections, and is a promising alternative to decrease sepsis during chemotherapy.

Daptomycin antibiotic lock therapy in a rat model of staphylococcal central venous catheter biofilm infections

Antibiotic lock therapy (ALT) is an adjunctive procedure to prevent or treat central venous catheter infections, ensuing catheter-related bacteremia, and catheter-related metastatic infections. Daptomycin is a cyclic lipopeptide that is rapidly bactericidal against methicillin-susceptible and -resistant Staphylococcus aureus. The efficacies of daptomycin against central venous catheter biofilms, catheter-related bacteremia, and catheter-related metastatic infections were evaluated by adapting a previously reported central venous catheter biofilm model in rats. Combined daptomycin ALT and systemic dosing resulted in the clearance of an established in vivo S. aureus central venous catheter biofilm after just two daily ALT treatments (30 min with daptomycin at 5 mg/ml) with concurrent systemic daptomycin dosing (40 mg/kg of body weight/day subcutaneously [s.c.]; equivalent exposure of 6 mg/kg/day in people). Daptomycin ALT solutions formulated in either saline or lactated Ringer's solution were equally fast in eradicating established in vivo methicillin-resistant Staphylococcus epidermidis (MRSE) central venous catheter biofilms. However, the lactated Ringer's formulation was superior to that of saline in sustaining the bacterial clearance of treated central venous catheters (83% versus 50%). In MRSE-infected central venous catheter studies, 3 days of daptomycin or vancomycin ALT (18 h at 5 mg/ml) with systemic s.c. dosing (40 mg/kg/day daptomycin or 100 mg/kg/day vancomycin) was equally effective 1 week posttherapy in maintaining cleared central venous catheters (90% [n = 10] versus 100% [n = 8]). These results suggest that daptomycin ALT, along with systemic dosing, could be an effective treatment option for the prevention or eradication of staphylococcal central venous catheter biofilm infections, thereby reducing the occurrence of catheter-related bacteremia or catheter-related metastatic infections.

Taurolidine lock is highly effective in preventing catheter-related bloodstream infections in patients on home parenteral nutrition: a heparin-controlled prospective trial

BACKGROUND & AIMS

Catheter-related bloodstream infections remain the major threat for Home Parenteral Nutrition programs. Taurolidine, a potent antimicrobial agent, holds promise as an effective catheter lock to prevent such infections. Aim of the present study was to compare taurolidine with heparin, the most frequently used lock, in this respect in these high-risk patients.

METHODS

Thirty patients from one referral centre for intestinal failure were enrolled after developing a catheter-related bloodstream infection. Following adequate treatment, either with or without a new access device (tunneled catheter or subcutaneous port), these patients were randomized to continue Home Parenteral Nutrition using heparin (n = 14) or taurolidine (n = 16) as catheter lock.

RESULTS

Whereas in controls 10 re-infections were observed, in the taurolidine group during 5370 catheter days only 1 re-infection occurred (mean infection-free survival 175 (95% CI 85-266; heparin) versus 641 (95% CI 556-727; taurolidine) days; log-rank p < 0.0001). No side effects or catheter occlusions were reported in either group. Moreover, after crossing-over of 10 patients with infections on heparin to taurolidine, only 1 new infection was observed.

CONCLUSION

Taurolidine lock dramatically decreased catheter-related bloodstream infections when compared with heparin in this high-risk group of Home Parenteral Nutrition patients.

[Stability: a factor to consider in antibiotic-lock solutions]

Antibiotic-lock therapy (ALT) has been related to a reduction in the need for catheter withdrawal in patients with catheter-related infection. The stability of the antimicrobial solutions used in ALT has not been sufficiently investigated. A systematic literature review was performed to identify articles including studies on the stability of ALT solutions. Nine studies fulfilled the inclusion criteria requiring specific drug determination techniques, and no apparent drug alterations were observed. The main microorganisms studied were Staphylococcus spp., Pseudomonas aeruginosa, and Klebsiella pneumoniae. The antibiotics included cefazolin, ceftazidime, ciprofloxacin, colistin, gentamicin, ticarcillin/clavulanate, and vancomycin in solution, administered alone or in combinations, with or without heparin. All solutions were fairly stable except for ciprofloxacin at a concentration of 10mg/mL. Few studies applied strict criteria to assess the stability of antibiotic solutions used in ALT; hence, the currently available data are limited. Therefore, it seems advisable to include appropriate stability studies in further research on the use of ALT.

The role of chelators in preventing biofilm formation and catheter-related bloodstream infections

PURPOSE OF REVIEW

As metallic cations are essential to microbial adherence, biofilm formation, and bacterial growth, efforts have been directed toward utilizing metal-binding chelators that have the capability of inhibiting bacterial growth by disrupting surface adherence and preventing biofilm production. This review focuses on recent advances in the role of chelators in biofilm disruption and prevention of catheter-related bloodstream infections.

RECENT FINDINGS

The most important factor in the pathogenesis of catheter-related bloodstream infections is the intraluminal colonization of the central venous catheters through the formation of bacterial biofilm matrix in which microbial organisms embed themselves and eventually become a source of catheter-related bloodstream infections. It has been demonstrated that high-affinity metal-binding chelators including ethylenediamine-tetraacetic acid and citrate have the capacity of inhibiting microbial growth by disrupting surface adherence and preventing biofilm production. Furthermore, ethylenediamine-tetraacetic acid and citrate have been clinically shown to be highly effective and outperform heparin in the prevention and treatment of catheter-related bloodstream infections when used as a component of antimicrobial catheter lock solutions.

SUMMARY

It is suggested that the addition of chelators such as ethylenediamine-tetraacetic acid and citrate to antimicrobial lock solutions provides an innovative and superior alternative to heparin lock solution in the prevention and treatment of catheter-related bloodstream infections.

Optimal antimicrobial catheter lock solution, using different combinations of minocycline, EDTA, and 25-percent ethanol, rapidly eradicates organisms embedded in biofilm

Antimicrobial lock solutions may be needed to salvage indwelling catheters in patients requiring continuous intravenous therapy. We determined the activity of minocycline, EDTA, and 25% ethanol, alone or in combination, against methicillin-resistant Staphylococcus aureus and Candida parapsilosis catheter-related bloodstream infection strains in two established models of biofilm colonization. Biofilm-colonized catheter segments from a modified Robbins device and a silicone disk biofilm colonization model were exposed to these antimicrobial agents for 15 or 60 min, respectively. After exposure, segments were sonicated and cultured. To determine regrowth after incubation at 37 degrees C, following the brief exposure to the antimicrobial agents, an equal number of segments were washed, reincubated for 24 h, and then sonicated and cultured. The triple combination of minocycline-EDTA (M-EDTA) in 25% ethanol was the only antimicrobial lock solution that completely eradicated S. aureus and C. parapsilosis in biofilm of all segments tested in the two models, and it completely prevented regrowth. In addition, M-EDTA in 25% ethanol was significantly more effective in rapidly eradicating the growth or regrowth of methicillin-resistant S. aureus and C. parapsilosis biofilm colonization in the two models than the other solutions--minocycline, EDTA, M-EDTA, 25% ethanol, and EDTA in ethanol. We conclude that M-EDTA in 25% ethanol is highly effective at rapidly eradicating S. aureus and C. parapsilosis embedded in biofilm adhering to catheter segments.

Comparison of Low-Dose Gentamicin With Minocycline as Catheter Lock Solutions in the Prevention of Catheter-Related Bacteremia

BACKGROUND

Catheter-restricted antibiotic lock solutions were found to be effective in the prevention of catheter-related bacteremia (CRB), but insufficient data are available about the ideal agent and dose. We hypothesized that a low concentration of gentamicin would be as effective as the high doses studied in the past.

METHODS

In this prospective, open-labeled, randomized, clinical trial of patients on long-term hemodialysis therapy, patients were randomly assigned to administration of an antibiotic lock solution of gentamicin/citrate (4 mg/mL), minocycline/EDTA, or the control solution of heparin. Patients were followed up until the study end point of CRB was reached or a censoring event occurred. Interim data analysis was performed after 6 months to assess data safety; efficacy was noted and the study was terminated early.

RESULTS

Sixty-two patients were enrolled into the study, evenly distributed in 3 arms, with data from 1 patient excluded from analysis. Seven of 20 patients in the heparin group (4.0 events/1,000 catheter days), 1 of 21 patients in the minocycline group (0.4 events/1,000 catheter days), and none of 20 patients in the gentamicin group developed bacteremia. Results were statistically significant by using 2-tailed Fisher exact test; heparin versus gentamicin, P = 0.008, and heparin versus minocycline, P = 0.020.

CONCLUSION

Antibiotic lock solutions are superior to the standard heparin lock alone in the prevention of CRBs, and low-dose gentamicin solution has efficacy similar to that of greater concentrations used in previous studies.

Antimicrobial locks: putting the lock on catheter infections

Infectious complications resulting from catheter use in the hemodialysis population remain as the significant cause of morbidity and mortality in this patient population. Because conservation of vascular access sites remains a therapeutic mainstay for chronic hemodialysis patients, clinical investigators have evaluated the safety and efficacy of catheter preservation with antimicrobial lock solutions instilled into the lumens of catheters to treat and prevent infectious complications. The recommended treatment of catheter-related bacteremia includes administration of systemic antibiotics with catheter removal. To date, 4 studies in the hemodialysis population have evaluated the use of systemic antibiotics with an antimicrobial lock solution for treatment of catheter-related bacteremias to amplify the success of catheter salvage. The use of antimicrobial lock solutions for the treatment of catheter-related bacteremia has resulted in successful catheter salvage in approximately 69% of patients, with the remainder requiring catheter removal following a lack of clinical improvement after 48 hours. The antimicrobial lock has also been studied as a prophylactic measure to prevent catheter-related bacteremia. Six studies in the hemodialysis population have evaluated the use of an antimicrobial lock for the prevention of catheter-related bacteremia with an overall 64%-100% reduction in the frequency of catheter-related bacteremia. Although the use of antimicrobial lock for prophylaxis has demonstrated efficacy in clinical trials, its long-term consequences, including potential impact on antimicrobial resistance, are unknown. The objectives of this review are to evaluate the current body of evidence espousing the utilization of an antimicrobial lock solution in tunneled cuffed and uncuffed catheters that are utilized during chronic intermittent hemodialysis.

Infections associated with medical devices: pathogenesis, management and prophylaxis

The insertion or implantation of foreign bodies has become an indispensable part in almost all fields of medicine. However, medical devices are associated with a definitive risk of bacterial and fungal infections. Foreign body-related infections (FBRIs), particularly catheter-related infections, significantly contribute to the increasing problem of nosocomial infections. While a variety of micro-organisms may be involved as pathogens, staphylococci account for the majority of FBRIs. Their ability to adhere to materials and to promote formation of a biofilm is the most important feature of their pathogenicity. This biofilm on the surface of colonised foreign bodies is regarded as the biological correlative for the clinical experience with FBRI, that is, that the host defence mechanisms often seem to be unable to handle the infection and, in particular, to eliminate the micro-organisms from the infected device. Since antibacterial chemotherapy is also frequently not able to cure these infections despite the use of antibacterials with proven in vitro activity, removal of implanted devices is often inevitable and has been standard clinical practice. However, in specific circumstances, such as infections of implanted medical devices with coagulase-negative staphylococci, a trial of salvage of the device may be justified. All FBRIs should be treated with antibacterials to which the pathogens have been shown to be susceptible. In addition to systemic antibacterial therapy, an intraluminal application of antibacterial agents, referred to as the 'antibiotic-lock' technique, should be considered to circumvent the need for removal, especially in patients with implanted long-term catheters. To reduce the incidence of intravascular catheter-related bloodstream infections, specific guidelines comprising both technological and nontechnological strategies for prevention have been established. Quality assurance, continuing education, choice of the catheter insertion site, hand hygiene and aseptic techniques are aspects of particular interest. Furthermore, all steps in the pathogenesis of biofilm formation may represent targets against which prevention strategies may be directed. Alteration of the foreign body material surface may lead to a change in specific and nonspecific interactions with micro-organisms and, thus, to a reduced microbial adherence. Medical devices made out of a material that would be antiadhesive or at least colonisation resistant would be the most suitable candidates to avoid colonisation and subsequent infection. Another concept for the prevention of FBRIs involves the impregnation of devices with various substances such as antibacterials, antiseptics and/or metals. Finally, further studies are needed to translate the knowledge on the mechanisms of biofilm formation into applicable therapeutic and preventive strategies.

Alteplase as a Catheter Locking Solution: In Vitro Evaluation of Biochemical Stability and Antimicrobial Properties

PURPOSE

To reduce potential complications of fibrin deposition to catheter surfaces, there is increasing empiric use of alteplase as a catheter lock solution. The purpose is to evaluate the properties of alteplase when reconstituted in sterile water (SW) or bacteriostatic water (BW) for prolonged periods.

MATERIALS AND METHODS

Alteplase in glass vials was reconstituted (1 mg/mL) with SW or BW (0.9% benzyl alcohol) in duplicates and stored at 37 degrees C. Biochemical assays were performed at days 0 and 7 and included optical clarity, protein concentration, percent protein monomer, and in vitro clot lysis activity. Microbiologic assays were performed on days 7 through 28 with use of a standardized antimicrobial effectiveness test (pass/fail) and pour-plate methods incubated at 22.5 degrees C (fungus, 3-7 days) or 32.5 degrees C (bacteria, 3-5 days). Organisms tested included Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Aspergillus niger.

RESULTS

Biochemical assay results were as follows: on day 0, all samples were clear/colorless; protein concentrations were 1.10 mg/mL +/- 0 in SW and 1.11 mg/mL +/- 0 in BW; percent protein monomer was 8.2% +/- 0.07 in SW and 98.6% +/- 0.07 in BW; and in vitro clot lysis activity (in percent of relative activity) was 100% in all samples. On day 7, all samples were clear/colorless, protein concentrations were 1.11 mg/mL +/- 0.07 in SW and 1.11 mg/mL +/- 0.07 in BW; percent protein monomer was 97.4% +/- 0.21 in SW and 96.1% +/- 0.21 in BW; and in vitro clot lysis activity (relative activity compared with day 0) was 91% +/- 2.8 in SW and 90% +/- 2.8 in BW. Microbiologic assays (US Pharmacopeia [USP] antimicrobial effectiveness test) yielded a failing result for alteplase reconstituted in SW and a passing result for alteplase reconstituted in BW.

CONCLUSIONS

Alteplase reconstituted with SW or BW remains relatively stable with retained bioactivity when stored at 37 degrees C for as long as 7 days. Despite the biochemical similarities of the two solutions, only alteplase in BW met USP criteria as an effective antimicrobial solution. Further clinical evaluation is warranted.

Antibiotic Lock Technique: A Review of the Literature

OBJECTIVE:

To review the literature on the use of the antibiotic lock technique (ALT) as a treatment option for patients with highly needed catheters.

DATA SOURCES:

MEDLINE and International Pharmaceutical Abstracts were searched (1980–August 2004). Search terms included antibiotic lock, catheter infection, and topical treatment.

STUDY SELECTION AND DATA EXTRACTION:

Articles describing use of ALT in the treatment of catheter infections in humans and studies evaluating in vitro stability of antibiotics were included.

DATA SYNTHESIS:

ALT has been used in patients with highly needed catheters, usually for parenteral nutrition, cancer chemotherapy, or dialysis. Catheters are considered highly needed when removal is not feasible or desirable due to lack of alternative injection sites for required therapy. Success rates in saving the infected catheter have been variable and may depend on the infecting organism. In addition, there are conflicting data in terms of compatibility of antibiotics with heparin solutions.

CONCLUSIONS:

Consensus appears to be that the ALT can be tried for patients with highly needed catheters when infection with coagulase-negative staphylococci is documented and no systemic signs of sepsis, such as hypotension, are evident. Most of these patients are likely to need systemic therapy as well. Infection of the catheter associated with systemic gram-negative bacteremia or fungemia will most likely require removal of the catheter to prevent systemic complications. Additional research with the ALT is warranted given unanswered questions.

Catheter-drawn blood cultures: is withdrawing the heparin lock beneficial?

AIMS

To assess the potential benefit of withdrawing or flushing away the heparin lock before collecting blood for culture from a central venous catheter.

METHODS

We compared the contamination rates of 152 pairs of blood samples aspirated from central venous catheters in afebrile renal dialysis or cancer patients. We also assessed the antimicrobial effect of 2000 U of heparin in Bactec Plus Aerobic/F culture bottles inoculated with a volunteer's blood plus one of six common bloodstream pathogens.

RESULTS

There was no significant difference in contamination rates between first-drawn (26 of 152, 17.1%) and second-drawn (24 of 152, 15.8%) samples. There was no significance difference in yield (58 of 60 [97%] versus 52 of 53 [98%]) or time to flagging positive (16.6 versus 16.7 h) between the bottles with and without heparin.

CONCLUSIONS

Our results do not support the practice of withdrawing or flushing away the heparin lock before collecting blood for culture from a central venous catheter.

Biofilm formation by Stenotrophomonas maltophilia: modulation by quinolones, trimethoprim-sulfamethoxazole, and ceftazidime

We investigated the in vitro effects of seven fluoroquinolones (ciprofloxacin, grepafloxacin, levofloxacin, moxifloxacin, norfloxacin, ofloxacin, and rufloxacin), compared to those of trimethoprim-sulfamethoxazole (SXT) and ceftazidime on total biomass and cell viability of Stenotrophomonas maltophilia biofilm. S. maltophilia attached rapidly to polystyrene, within 2 h of incubation, and then biofilm formation increased over time, reaching maximum growth at 24 h. In the presence of fluoroquinolones at one-half and one-fourth the MIC, biofilm biomass was significantly (P < 0.01) reduced to 55 to 70% and 66 to 76% of original mass, respectively. Ceftazidime and SXT did not exert any activity. Biofilm bacterial viability was significantly reduced by all antibiotics tested at one-half the MIC. At one-fourth the MIC all antibiotics, except levofloxacin, significantly reduced viability. Treatment of preformed biofilms with bactericidal concentrations (500, 100, and 50 micro g/ml) of all fluoroquinolones caused, except for norfloxacin, significant reduction of biofilm biomass to 29.5 to 78.8, 64.1 to 83.6, and 70.5 to 82.8% of original mass, respectively. SXT exerted significant activity at 500 micro g/ml only. Ceftazidime was completely inactive. Rufloxacin exhibited the highest activity on preformed biofilm viability, significantly decreasing viable counts by 0.6, 5.4, and 17.1% at 500, 100, and 50 micro g/ml, respectively. Our results show that (i) subinhibitory (one-half and one-fourth the MIC) concentrations of fluoroquinolones inhibit adherence of S. maltophilia to polystyrene and (ii) clinically achievable concentrations (50 and 100 micro g/ml) of rufloxacin are able to eradicate preformed S. maltophilia biofilm.

Antimicrobial activity of a novel catheter lock solution

Intravascular catheter-associated bloodstream infections significantly increase rates of morbidity and hospital costs. Microbial colonization and development of biofilms, which are known to be recalcitrant to antibiotic therapy, often lead to the loss of otherwise patent vascular access systems. We evaluated a new taurolidine- and citrate-based catheter lock solution (Neutrolin; Biolink Corporation, Norwell, Mass.) for its activity against planktonic microbes, antimicrobial activity in a catheter model, and biofilm eradication activity. In studies of planktonic microbes, after 24 h of contact, 675 mg of taurolidine-citrate solution per liter caused > 99% reductions in the initial counts of Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Entercoccus faecalis. A solution of 13,500 mg/liter was cidal for Candida albicans. Ports and attached catheters inoculated with 50 to 600 CFU of these bloodstream isolates per ml were locked with heparin or the taurolidine-citrate solution. After 72 h, there was no growth in the taurolidine-citrate-treated devices but the heparin-treated devices exhibited growth in the range of 6 x 10(2) to 5 x 10(6) CFU/ml. Biofilms were developed on silicone disks in modified Robbins devices with broth containing 6% serum (initial counts, 10(6) to 10(8) CFU/cm(2)). The axenic biofilms were treated for 24 h with taurolidine-citrate or heparin. Taurolidine-citrate exposure resulted in a median reduction of 4.8 logs, whereas heparin treatment resulted in a median reduction of 1.7 logs (P < 0.01). No significant differences in the effects of the two treatments against P. aeruginosa and C. albicans were observed. These findings suggest that taurolidine-citrate is a promising combination agent for the prevention and treatment of intravascular catheter-related infections.