Intravascular catheters impregnated with antimicrobial agents: a milestone in the prevention of bloodstream infections

Our Experience over 20 Years: Antimicrobial Peptides against Gram Positives, Gram Negatives, and Fungi

Antibiotic resistance is rapidly increasing, and new anti-infective therapies are urgently needed. In this regard, antimicrobial peptides (AMPs) may represent potential candidates for the treatment of infections caused by multiresistant microorganisms. In this narrative review, we reported the experience of our research group over 20 years. We described the AMPs we evaluated against Gram-positive, Gram-negative, and fungi. In conclusion, our experience shows that AMPs can be a key option for treating multiresistant infections and overcoming resistance mechanisms. The combination of AMPs allows antibiotics and antifungals that are no longer effective to exploit the synergistic effect by restoring their efficacy. A current limitation includes poor data on human patients, the cost of some AMPs, and their safety, which is why studies on humans are needed as soon as possible.

The potential for developing new antimicrobial resistance from the use of medical devices containing chlorhexidine, minocycline, rifampicin and their combinations: a systematic review

Background

Catheter infections remain one of the most persistent adverse events causing significant morbidity, economic impact and mortality. Several strategies have been proposed to reduce these infections including the use of catheters embedded with antibiotics and/or antiseptics. One reoccurring challenge is the fear that antimicrobial medical devices will induce resistance. The aim of this systematic review is to evaluate the evidence for induced antimicrobial resistance caused by exposure to antimicrobial medical devices.

Methods

Four electronic databases [MEDLINE, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL) and Scopus] were screened for studies published between 1983 and 2019 regarding assessment of microbial resistance with use of medical devices containing chlorhexidine, minocycline, rifampicin or combinations thereof. Development of new resistance, selection for tolerant organisms and 'no change in resistance' were assessed.

Results

Forty-four publications, grouped by study type and stratified by drug assessed, were included for analyses. The majority of studies found no change in resistance after exposure to antimicrobial medical devices (13 in vitro, 2 in vivo, 20 clinical). Development of new resistance was commonly reported with the use of rifampicin as a single agent and only reported in one study assessing the minocycline/rifampicin combination (M/R); however, the increase in MIC was well below clinical relevance.

Conclusions

Emergence of new resistance to combinations of M/R, minocycline/rifampicin/chlorhexidine (M/R/CH) and chlorhexidine/silver sulfadiazine (CHXSS) was rare. No clinical trials confirmed its occurrence and some refuted it. The risk of development of new resistance to these antimicrobial combinations appears more fear-based than substantiated by clinical and experimental evidence but warrants continued surveillance.

Inhibition of Staphylococcus Epidermidis Colonization with Fusidic Acid-Impregnated Catheters

The aim of this study was the preparation and characterization of fusidic acid-impregnated peripheral catheters. In the first part of the study, in vitro drug release studies were performed, and the effect of fusidic acid impregnation on adherence of slime positive Staphylococcus epidermidis to catheters was evaluated as in vitro studies. Fusidic acid-impregnated and naïve catheters were incubated with 108 colony forming unit/mL (cfu/mL) slime positive S. epidermidis during the in vitro experiment. After incubation for 2, 4, 6, 8, 12, 24, 48, and 72 h, the number of colonies were determined in an aliquot and adhered to the catheter. During the in vivo experiment, contaminated naïve and fusidic acid-impregnated catheters ( n = 10 rats in both groups) were implanted subcutaneously in the back of the rats. Rats were killed at the end of the seventh day and catheters were removed. Microbiologic assessments from the explanted catheter segments were performed. Fusidic acid impregnation decreased the number of adherent bacteria to the catheters and the number of free bacteria within the liquid medium significantly. There were 3 positive catheter cultures out of 10 in rats implanted with fusidic acid-impregnated catheters, whereas all explanted catheters from naïve group yielded bacterial growth. The mean cfu counts were significantly less in the fusidic acid-impregnated catheter group. In vitro release studies and antibacterial activity studies correlated well. Additionally, morphological evaluations by scanning electron microscopy showed that fewer bacteria were evident on the fusidic acid-impregnated catheters compared with naïve catheters. As a conclusion, catheter impregnation with fusidic acid is effective in preventing colonization in these in vitro and in vivo sets of experiments, with slime-producing S. epidermidis.

Synthesis of eucalyptus/tea tree oil absorbed biphasic calcium phosphate–PVDF polymer nanocomposite films: a surface active antimicrobial system for biomedical application

A biocompatible poly(vinylidene) difluoride (PVDF) based film has been prepared by in situ precipitation of calcium phosphate precursors.

Gold nanoshell-decorated silicone surfaces for the near-infrared (NIR) photothermal destruction of the pathogenic bacterium E. faecalis

Catheter-related infections (CRIs) are associated with the formation of pathogenic biofilms on the surfaces of silicone catheters, which are ubiquitous in medicine. These biofilms provide protection against antimicrobial agents and facilitate the development of bacterial resistance to antibiotics. The application of photothermal agents on catheter surfaces is an innovative approach to overcoming biofilm-generated CRIs. Gold nanoshells (AuNSs) represent a promising photothermal tool, because they can be used to generate heat upon exposure to near-infrared (NIR) radiation, are biologically inert at physiological temperatures, and can be engineered for the photothermal ablation of cells and tissue. In this study, AuNSs functionalized with carboxylate-terminated organosulfur ligands were attached to model catheter surfaces and tested for their effectiveness at killing adhered Enterococcus faecalis (E. faecalis) bacteria. The morphology of the AuNSs was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while the elemental composition was characterized by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Furthermore, optical and photothermal properties were acquired by ultraviolet-visible (UV-vis) spectroscopy and thermographic imaging with an infrared camera, respectively. Bacterial survival studies on AuNS-modified surfaces irradiated with and without NIR light were evaluated using a colony-formation assay. These studies demonstrated that AuNS-modified surfaces, when illuminated with NIR light, can effectively kill E. faecalis on silicone surfaces.

Up for the Challenge: Eliminating Peripherally Inserted Central Catheter Infections in a Complex Patient Population

Background: In response to Medicare reimbursement changes related to central line-associated blood stream infection (CLABSI) effective January 2011, a long-term acute care hospital implemented quality improvement measures to reduce these health care-associated infections. Improvements included alcohol-impregnated port protectors, chlorhexidine gluconate barrier dressings, and didactic/hands on training for care and maintenance. During 2010 the peripherally inserted central line (PICC) team at a neighboring Magnet hospital was asked to partner and develop strategies to further decrease CLABSI.

Methods: The PICC team evaluated the effects of an antimicrobial PICC device in an effort to further reduce the incidence of CLABSI. Upon initiation of the evaluation phase, a database was created to track infection/thrombus rate, insertion-related complications, dwell time, diagnosis, tip location, infusate, vein used, and catheter size. Data collection and reporting was managed by the PICC team.

Results: Across a 2-year period (July 2011–July 2013), 100 devices were inserted with a total of 1,705 line days without any reported CLABSI. The majority of patients received a 4.5F single lumen device (59%). Dwell time ranged from 1 to 57 days with an average of 17 days. To date, no CLABSIs related to this device have been reported at the long-term acute care hospital.

Conclusions: Based on 100 insertions yielding no infections this new product appears to improve patient safety and quality of care. Relative to these results sole use of this product has become their institutional standard for long-term intravenous needs.

Pseudomonas aeruginosa biofilms in disease

Pseudomonas aeruginosa is a ubiquitous organism that is the focus of intense research because of its prominent role in disease. Due to its relatively large genome and flexible metabolic capabilities, this organism exploits numerous environmental niches. It is an opportunistic pathogen that sets upon the human host when the normal immune defenses are disabled. Its deadliness is most apparent in cystic fibrosis patients, but it also is a major problem in burn wounds, chronic wounds, chronic obstructive pulmonary disorder, surface growth on implanted biomaterials, and within hospital surface and water supplies, where it poses a host of threats to vulnerable patients (Peleg and Hooper, N Engl J Med 362:1804-1813, 2010; Breathnach et al., J Hosp Infect 82:19-24, 2012). Once established in the patient, P. aeruginosa can be especially difficult to treat. The genome encodes a host of resistance genes, including multidrug efflux pumps (Poole, J Mol Microbiol Biotechnol 3:255-264, 2001) and enzymes conferring resistance to beta-lactam and aminoglycoside antibotics (Vahdani et al., Annal Burns Fire Disast 25:78-81, 2012), making therapy against this gram-negative pathogen particularly challenging due to the lack of novel antimicrobial therapeutics (Lewis, Nature 485: 439-440, 2012). This challenge is compounded by the ability of P. aeruginosa to grow in a biofilm, which may enhance its ability to cause infections by protecting bacteria from host defenses and chemotherapy. Here, we review recent studies of P. aeruginosa biofilms with a focus on how this unique mode of growth contributes to its ability to cause recalcitrant infections.

A review of the biomaterials technologies for infection-resistant surfaces

Anti-infective biomaterials need to be tailored according to the specific clinical application. All their properties have to be tuned to achieve the best anti-infective performance together with safe biocompatibility and appropriate tissue interactions. Innovative technologies are developing new biomaterials and surfaces endowed with anti-infective properties, relying either on antifouling, or bactericidal, or antibiofilm activities. This review aims at thoroughly surveying the numerous classes of antibacterial biomaterials and the underlying strategies behind them. Bacteria repelling and antiadhesive surfaces, materials with intrinsic antibacterial properties, antibacterial coatings, nanostructured materials, and molecules interfering with bacterial biofilm are considered. Among the new strategies, the use of phages or of antisense peptide nucleic acids are discussed, as well as the possibility to modulate the local immune response by active cytokines. Overall, there is a wealth of technical solutions to contrast the establishment of an implant infection. Many of them exhibit a great potential in preclinical models. The lack of well-structured prospective multicenter clinical trials hinders the achievement of conclusive data on the efficacy and comparative performance of anti-infective biomaterials.

An in vivo rabbit model for the evaluation of antimicrobial peripherally inserted central catheter to reduce microbial migration and colonization as compared to an uncoated PICC

Infection is the leading complication associated with intravascular devices, and these infections develop when a catheter becomes colonized by microorganisms. To combat this issue, medical device manufacturers seek to provide healthcare facilities with antimicrobial medical devices to prevent or reduce the colonization. In order to adequately evaluate these devices, an in vivo model is required to accurately assess the performance of the antimicrobial devices in a clinical setting. The model presented herein was designed to provide a simulation of the subcutaneous tunnel environment to evaluate the ability of an antimicrobial peripherally inserted central catheter (PICC), coated with chlorhexidine based technology, to reduce microbial migration and colonization compared to an uncoated PICC. Three samples of control, uncoated PICCs and three samples of coated PICCs were surgically tunneled into the backs of female New Zealand White rabbits. The insertion sites were then challenged with Staphylococcus aureus at the time of implantation. Animals were evaluated out to thirty days and sacrificed. Complete en bloc dissection and evaluation of the catheter and surrounding tissue demonstrated that the chlorhexidine coated catheter was able to significantly reduce microbial colonization and prevent microbial migration as compared to the standard, un-treated catheter.

Rifampin combination therapy for nonmycobacterial infections

The increasing emergence of antimicrobial-resistant organisms, especially methicillin-resistant Staphylococcus aureus (MRSA), has resulted in the increased use of rifampin combination therapy. The data supporting rifampin combination therapy in nonmycobacterial infections are limited by a lack of significantly controlled clinical studies. Therefore, its current use is based upon in vitro or in vivo data or retrospective case series, all with major limitations. A prominent observation from this review is that rifampin combination therapy appears to have improved treatment outcomes in cases in which there is a low organism burden, such as biofilm infections, but is less effective when effective surgery to obtain source control is not performed. The clinical data support rifampin combination therapy for the treatment of prosthetic joint infections due to methicillin-sensitive S. aureus (MSSA) after extensive debridement and for the treatment of prosthetic heart valve infections due to coagulase-negative staphylococci. Importantly, rifampin-vancomycin combination therapy has not shown any benefit over vancomycin monotherapy against MRSA infections either clinically or experimentally. Rifampin combination therapy with daptomycin, fusidic acid, and linezolid needs further exploration for these severe MRSA infections. Lastly, an assessment of the risk-benefits is needed before the addition of rifampin to other antimicrobials is considered to avoid drug interactions or other drug toxicities.

Characterization of crosslinking effects on the physicochemical and drug diffusional properties of cationic hydrogels designed as bioactive urological biomaterials

This study examined the effects of concentration and type of crosslinker (tetraethyleneglycol diacrylate, TEGDA; diethyleneglycol dimethacrylate, DEGDMA; and polyethyleneglycol dimethacrylate, PEGDMA) on the mechanical and drug diffusional properties of hydrogels that had been selected as candidate coatings for bioactive medical devices. Hydrogels (dimethylaminoethylmethacrylate-covinylpyrrolidone; 1:1) were prepared by free radical polymerization and characterized using tensile analysis, dynamic contact angle analysis and analysis of swelling at pH 6.0. The release of fusidic acid and chlorhexidine was evaluated using buffered medium at pH 6.0 and, in addition, using dissolution medium that had been buffered to pH 9 in the presence and absence of elevated concentrations of calcium, representative of urinary encrustation. Crosslinker concentration, but not type, affected the advancing and receding contact angles. Conversely, both crosslinker type and concentration affected the mechanical and swelling properties of the hydrogels. Maximum swelling and elongation at break were associated with the PEGDMA-crosslinked hydrogels whereas TEGDA-crosslinked hydrogels exhibited the maximum ultimate tensile strength and Young's modulus. Drug release from all systems occurred by diffusion. The mass of chlorhexidine and fusidic acid released was dependent on crosslinker type and concentration, with hydrogels crosslinked with PEGDMA offering the greatest mass of drug released at each sampling period. The mass of fusidic acid but not chlorhexidine released at pH 9.0 in a calcium augmented medium was lower than that released in the same medium devoid of elevated calcium, due to the formation of the poorly soluble calcium salt. In conclusion, this study has uniquely examined the effects of crosslinker type and concentration on physicochemical and drug release properties essential to the clinical and non-clinical performance of bioactive hydrogels for medical device application.

Antibiotic synergy against biofilm-forming Pseudomonas aeruginosa

Eight antibiotics (aztreonam, ceftazidim, cefoperazon, cefepim, netilmicin, amikacin, ofloxacin and ciprofloxacin) exhibited antimicrobial activity individually and/or in combinations against 20 wild-type biofilm-forming strains of Pseudomonas aeruginosa. The strains were less susceptible in biofilm; in 10 strains antibiotic synergy was observed for the combination of aztreonam and ciprofloxacin. Synergy was also demonstrated in the case of beta-lactams and aminoglycosides, beta-lactams and fluoroquinolones, aminoglycosides and fluoroquinolones, and for monobactams and beta-lactams although the strains were resistant to the individual antibiotics. Synergism or partial synergism was found with one or more antibiotic combinations against 32.4% of isolates.

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.

Effect of coating the wells of a polystyrene microtiter plate with xanthorrhizol on the biofilm formation of Streptococcus mutans

Colonization on the surface of tooth by Streptococcus mutans is an important step in the initiation of dental plaque. Polystyrene microtiter plates have been employed to study bacterial colonization and biofilm formation of periodontal bacteria. The objective of this work was to evaluate the effect of coating the wells of a polystyrene microtiter plate with xanthorrhizol isolated from java turmeric (Curcuma xanthorrhiza Roxb.) on Strep. mutans biofilm formation. Our studies demonstrated that coating of a polystyrene microtiter plate with 5 microg/ml of xanthorrhizol resulted in significant (up to 60%) reduction of adherent cells compared to that of cells in uncoated wells. This result suggests that xanthorrhizol displays potent activity in preventing Strep. mutans biofilm formation.

Pre-treatment of central venous catheters with the cathelicidin BMAP-28 enhances the efficacy of antistaphylococcal agents in the treatment of experimental catheter-related infection

An in vitro antibiotic susceptibility assay for Staphylococcus aureus biofilms developed on 96-well polystyrene tissue culture plates was performed to elucidate the activity of the 27 residues cathelicidin peptide BMAP-28, quinupristin/dalfopristin (Q/D), linezolid, and vancomycin. Efficacy studies were performed in a rat model of staphylococcal CVC infection. Silastic catheters were implanted into the superior cava. Twenty-four hours after implantation the catheters were filled with BMAP-28. Thirty minutes later rats were challenged via the CVC with 1.0x10(6) CFU of S. aureus strain Smith diffuse. Administration of antibiotics into the CVC at a concentration equal to the MBC observed using adherent cells, or at a much higher concentration (1024 microg/mL) began 24 h later. The inhibition activities of all antibiotics against adherent bacteria were at least two-four-fold lower that against freely growing cells. When antibiotics were used in BMAP-28 pre-treated wells, they showed higher activities. The in vivo studies showed that when CVCs were pre-treated with BMAP-28 or with a high dose of antibiotics, biofilm bacterial load was reduced from 10(7) to 10(3) CFU/mL and bacteremia reduced from 10(3) to 10(1) CFU/mL. When CVCs were treated with both BMAP-28 and antibiotics, biofilm bacterial load was further decreased to 10(1) CFU/mL and bacteremia was not detected. These results suggest that CVC pre-treated with BMAP-28 represents an attractive choice for the treatment of device-related infections caused by staphylococci.

Citropin 1.1-treated central venous catheters improve the efficacy of hydrophobic antibiotics in the treatment of experimental staphylococcal catheter-related infection

An in vitro antibiotic susceptibility assay for Staphylococcus aureus biofilms developed on 96-well polystyrene tissue culture plates was performed to elucidate the activity of citropin 1.1, rifampin and minocycline. Efficacy studies were performed in a rat model of staphylococcal CVC infection. Silastic catheters were implanted into the superior cava. Twenty-four hours after implantation the catheters were filled with citropin 1.1 (10 microg/mL). Thirty minutes later the rats were challenged via the CVC with 1.0 x 10(6) CFU of S. aureus strain Smith diffuse. Administration of antibiotics into the CVC (the antibiotic lock technique) began 24 h later. The study included: one control group (no CVC infection), one contaminated group that did not receive any antibiotic prophylaxis, one contaminated group that received citropin 1.1-treated CVC, two contaminated groups that received citropin 1.1-treated CVC plus rifampin and minocycline at concentrations equal to MBCs for adherent cells and 1024 microg/mL in a volume of 0.1 mL that filled the CVC and two contaminated groups that received rifampin or minocycline at the same concentrations. All catheters were explanted 7 days after implantation. Main outcome measures were: minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), synergy studies, quantitative culture of the biofilm formed on the catheters and surrounding venous tissues, and quantitative peripheral blood cultures. MICs of conventional antibiotics against the bacteria in a biofilm were at least four-fold higher than against the freely growing planktonic cells. In contrast, when antibiotics were used on citropin 1.1 pre-treated cells they showed comparable activity against both biofilm and planktonic organisms. The in vivo studies show that when CVCs were pre-treated with citropin 1.1 or with a high dose of antibiotics, biofilm bacterial load was reduced from 10(7) to 10(3) CFU/mL and bacteremia reduced from 10(3) to 10(1) CFU/mL. When CVCs were treated both with citropin 1.1 and antibiotics, biofilm bacterial load was further reduced to 10(1) CFU/mL and bacteremia was not detected, suggesting 100% elimination of bacteremia and a log 6 reduction in biofilm load. Citropin 1.1 significantly reduces bacterial load and enhances the effect of hydrophobic antibiotics in the treatment of CVC-associated S. aureus infections.

The significance of infection related to orthopedic devices and issues of antibiotic resistance

Over the last 15 years, with the advent of modern standards in the control of sterility within the operating room environment and adequate protocols of peri-operative antibiotic prophylaxis, the incidence of infections associated to orthopedic implants has become very low. Nevertheless, the event of infection still represents one of the most serious and devastating complications which may involve prosthetic devices. It leads to complex revision procedures and, often, to the failure of the implant and the need for its complete removal. In orthopedics, for the enormous number of surgical procedures involving invasive implant materials, even if nowadays rare, infections have a huge impact in terms of morbidity, mortality, and medical costs. The difficult battle to prevent and fight bacterial infections associated to prosthetic materials must be played on different grounds. A winning strategy requires a clear view of the pathogenesis and the epidemiology of implant-related infections, with a special attention on the alarming phenomenon of antibiotic resistance. In this regard staphylococci are the prevalent and most important causative pathogens involved in orthopedic implant-related infections, and, thus, the main enemy to defeat. In this paper, we offer an overview of the complexity of this battleground and of the current and new, in our opinion most promising, strategies in the field of biomaterials to reduce the risks and counteract the establishment of implant infections.

Infection control issues in central venous catheter care

Central venous catheters (CVCs) are now a routine part of patient management in the intensive care unit (ICU). Over time, a vast amount of literature associated with the use and care of CVCs has accumulated. The purpose of this article is to discuss the literature associated with the care of these devices in a narrative format. Although particular attention is paid to infection control issues, other fundamental areas such as catheter design, dressings, line changing and post insertion management are also discussed. The article goes on to look at the future of CVC design and concludes with an analysis of future developments related to CVCs.

Are Antimicrobial-Impregnated Catheters Effective? Replace the Water and Grab Your Washcloth, Because We Have a Baby to Wash

Significant controversy surrounds the usefulness of central venous catheters (CVCs) impregnated with antimicrobial agents (A-CVCs) for the prevention of catheter-related bloodstream infections (CRBSIs). In a recent issue of Clinical Infectious Diseases, we reviewed 11 published trials of A-CVCs versus uncoated CVCs, and we concluded that there is a lack of solid evidence to support a benefit of A-CVCs in reducing the rate of CRBSIs. A response to our review was recently published in Clinical Infectious Diseases. In this response, our colleagues assert that there is a large body of evidence that demonstrates a powerful decrease in the risk of infection, and they conclude that we should not waste precious resources while we perform additional research to confirm what we have already found to be true. Although these authors agree with us on the significant shortcomings of the studies used to support the use of A-CVCs, they dismiss the need for additional trials to demonstrate that the use of A-CVCs does reduce infections. This dismissal, however, cannot be justified, because of the existence of an ongoing, federally supported, multicenter, prospective, placebo-controlled trial, led by our colleagues, that compares the rate of CRBSIs among patients randomized to receive either an A-CVC or a "placebo" uncoated CVC. That our colleagues are leading a trial that assesses the efficacy of A-CVCs versus placebo uncoated CVCs supports our viewpoint that the truth regarding the protective role of A-CVCs has yet to be determined. Because of the significant cost, potential toxicity, and risk of increased antimicrobial resistance associated with the use of A-CVCs, and until the results of the important trial conducted by our colleagues convincingly demonstrate that A-CVCs reduce the rate of clinically significant events (not just catheter colonization), we recommend that the use of A-CVCs be limited to investigational settings.

Catheter-Related Focal FDG Activity on Whole Body PET Imaging

INTRODUCTION

Whole body FDG positron emission tomography (PET) scan is increasingly being used in the management of a variety of cancers and infections. Cancer patients and other very sick patients have central venous catheters, which could be associated with common complications like thrombosis and infections. We describe catheter-related focal FDG uptake on whole body FDG PET scans in 4 patients.

MATERIALS AND METHODS

Four patients underwent whole body FDG-PET scanning 60 minutes after intravenous injection of F18-FDG (2 for localization of site of infection, 1 for primary cancer site localization, and 1 for restaging of colon cancer). The whole body PET images were compared and correlated with the patients' history, radiology and laboratory tests.

RESULTS

Focal and intense FDG activity is seen in all 4 patients at the distal end of the intravenous catheter. The average SUV of this activity was 6.3 (n = 3). Catheter-related thrombosis was identified as the cause of FDG activity in 3 patients, whereas catheter-related infection was considered in one patient.

CONCLUSION

Focal and intense FDG activity, in relation to the distal end of a central venous catheter, has a benign etiology, usually seen with catheter-related venous thrombosis and can be seen with catheter related infection.

In situ revascularization with silver-coated polyester grafts to treat aortic infection: early and midterm results

PURPOSE

In this prospective study we analyzed the immediate and midterm outcome in patients with abdominal aorta infection (mycotic aneurysm, prosthetic graft infection) managed by excision of the aneurysm or the infected vascular prosthesis and in situ replacement with a silver-coated polyester prosthesis.

METHODS

From January 2000 to December 2001, 27 consecutive patients (25 men, 2 women; mean age, 69 years) with an abdominal aortic infection were entered in the study at seven participating centers. Infection was managed with either total (n = 18) or partial (n = 6) excision of the infected aorta and in situ reconstruction with an InterGard Silver (IGS) collagen and silver acetate-coated polyester graft. Assessment of outcome was based on survival, limb salvage, persistent or recurrent infection, and prosthetic graft patency.

RESULTS

Twenty-four patients had prosthetic graft infections, graft-duodenal fistula in 12 and graft-colonic fistula in 1; and the remaining 3 patients had primary aortic infections. Most organisms cultured were of low virulence. The IGS prosthesis was placed emergently in 11 patients (41%). Mean follow-up was 16.5 months (range, 3-30 months). Perioperative mortality was 15%; all four patients who died had a prosthetic graft infection. Actuarial survival at 24 months was 85%. No major amputations were noted in this series. Recurrent infection developed in only one patient (3.7%). Postoperative antibiotic therapy did not exceed 3 months, except in one patient. No incidence of prosthetic graft thrombosis was noted during follow-up.

CONCLUSION

Preliminary results in this small series demonstrate favorable outcome with IGS grafts used to treat infection in abdominal aortic grafts and aneurysms caused by organisms with low virulence. Larger series and longer follow-up will be required to compare the role of IGS grafts with other treatment options in infected fields.

In vitro activity of caspofungin against Candida albicans biofilms

Most manifestations of candidiasis are associated with biofilm formation on biological or inanimate surfaces. Candida albicans biofilms are recalcitrant to treatment with conventional antifungal therapies. Here we report on the activity of caspofungin, a new semisynthetic echinocandin, against C. albicans biofilms. Caspofungin displayed potent in vitro activity against sessile C. albicans cells within biofilms, with MICs at which 50% of the sessile cells were inhibited well within the drug's therapeutic range. Scanning electron microscopy and confocal scanning laser microscopy were used to visualize the effects of caspofungin on preformed C. albicans biofilms, and the results indicated that caspofungin affected the cellular morphology and the metabolic status of cells within the biofilms. The coating of biomaterials with caspofungin had an inhibitory effect on subsequent biofilm development by C. albicans. Together these findings indicate that caspofungin displays potent activity against C. albicans biofilms in vitro and merits further investigation for the treatment of biofilm-associated infections.

Intravenous access: related problems in oncology

This article reviews the latest developments in the literature concerning two types of catheter widely used in oncology: Hickman central venous catheters (CVCs) and totally implanted venous ports. It now seems possible to diagnose catheter-related bloodstream infections (CRBI) without removing the device; recent studies showed that paired quantitative blood cultures are the most reliable and convenient method for diagnosis of CRBI. Can CRBI be cured and treated without device removal? A decision-tree/flow-chart resulting from analysis of international data by French International Experts is presented. Futures trends are reviewed: new techniques for prevention, including catheters impregnated with antimicrobials and, antiseptic hubs; flushing and antibiotic lock techniques that can be used both for prevention and treatment.

Biomaterials to prevent nosocomial infections: is silver the gold standard?

Although many antimicrobial biomaterials have shown promising activity in vitro, few anti-infective prosthetic devices manufactured from these materials have yet achieved any degree of success in clinical trials. Controversy surrounds the exploitation of antibiotics in these materials and the microbiological methods that have been used in the clinical trials on the devices.

Indications and complications of intravenous devices for chemotherapy

Vascular access devices (VADs) are frequently used in patients with cancer. Vascular access devices can be divided into external catheters and subcutaneous venous access ports. Each type of device has its advantages and disadvantages, but the indications and optimal use of specific VADs remain to be defined. There are multiple complications of VADs but, with the exception of catheter-related bloodstream infections and thrombosis, most complications are rare. The use of VADs impregnated with antibiotic reduces the rates of catheter colonization and catheter-related bloodstream infections as compared with the use of unimpregnated catheters for short-term use. Thrombosis remains a major complication of VADs, and prospective, controlled studies are needed to clearly define the risk factors, natural history, and optimal treatment of this complication.

Toward new biomaterials

Polymers are widely used for a large range of medical devices used as biomaterials on a temporary, intermittent, and long-term basis. It is now well accepted that the initial rapid adsorption of proteins to polymeric surfaces affects the performance of these biomaterials. However, protein adsorption to a polymer surface can be modulated by an appropriate design of the interface. Extensive study has shown that these interactions can be minimized by coating with a highly hydrated layer (hydrogel), by grafting on the surface different biomolecules, or by creating domains with chemical functions (charges, hydrophilic groups). Our laboratory has investigated the latter approach over the past 2 decades, in particular the synthesis and the biological activities of polymers to improve the biocompatibility of blood-contacting devices. These soluble and insoluble polymers were obtained by chemical substitution of macromolecular chains with suitable groups able to develop specific interactions with biological components. Applied to compatibility with the blood and the immune systems, this concept has been extended to interactions of polymeric biomaterials with eukaryotic and prokaryotic cells. The design of new biomaterials with low bacterial attachment is thus under intensive study. After a brief overview of current trends in the surface modifications of biocompatible materials, we will describe how biospecific polymers can be obtained and review our recent results on the inhibition of bacterial adhesion using one type of functionalized polymer obtained by random substitution. This strategy, applied to existing or new materials, seems promising for the limitation of biomaterial-associated infections.