Impact of microbial attachment on intravascular catheter-related infections

Design of Thermoplastic Polyurethanes with Conferred Antibacterial, Mechanical, and Cytotoxic Properties for Catheter Application

Thermoplastic polyurethanes (TPUs) are proposed as suitable solution for the fabrication of biocompatible catheters with appropriate mechanical parameters and confirmed antibacterial and cytocompatible properties. For this purpose, a series of quaternary ammonium salts (QASs) and quaternary phosphonium salts (QPSs) based monomers were prepared followed by the determination of their minimal inhibitory concentrations (MICs) against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Pseudomonas aeruginosa (P. aeruginosa). A combination of the most active ammonium (QAS-C₁₄) and phosphonium (QPS-TOP) salts led to a MIC down to 2.4 μg/mL against S. aureus and 9 μg/mL against P. aeruginosa, corroborating the existence of a synergistic effect. These quaternary onium salt (QOS) units were successfully incorporated along the polymer chain, as part of a two-step synthesis approach. The resulting TPU-QOS materials were subsequently characterized through thermal, mechanical, and surface analyses. TPU-Mix (combining the most active QAS-C₁₄ and QPS-TOP units) showed the highest antibacterial efficiency, confirming the synergistic effect between both QOS groups. Finally, an MTT assay on the SiHa cell line revealed the low cytotoxicity level of these polymeric films, making these materials suitable for biomedical application. To go one step further in the preindustrialization approach, proof of concept regarding the catheter prototype fabrication based on TPU-QAS/QPS was validated by extrusion.

The microbial biofilm composition on peripherally inserted central catheters: A comparison of polyurethane and hydrophobic catheters collected from paediatric patients

BACKGROUND

Peripherally inserted central catheters are susceptible to microbial colonisation and subsequent biofilm formation, leading to central line-associated bloodstream infection, a serious peripherally inserted central catheter-related complication. Next-generation peripherally inserted central catheter biomaterials, such as hydrophobic materials (e.g. Endexo^®), may reduce microbial biofilm formation or attachment, consequently reducing the potential for central line-associated bloodstream infection.

METHODS

Within a randomised controlled trial, culture-dependent and culture-independent methods were used to determine if the biomaterials used in traditional polyurethane peripherally inserted central catheters and hydrophobic peripherally inserted central catheters impacted microbial biofilm composition. This study also explored the impact of other clinical characteristics including central line-associated bloodstream infection, antibiotic therapy and dwell time on the microbial biofilm composition of peripherally inserted central catheters.

RESULTS

From a total of 32 patients, one peripherally inserted central catheter was determined to be colonised with Staphylococcus aureus, and on further analysis, the patient was diagnosed with central line-associated bloodstream infection. All peripherally inserted central catheters (n = 17 polyurethane vs n = 15 hydrophobic) were populated with complex microbial communities, including peripherally inserted central catheters considered non-colonised. The two main microbial communities observed included Staphylococcus spp., dominant on the colonised peripherally inserted central catheter, and Enterococcus, dominant on non-colonised peripherally inserted central catheters. Both the peripherally inserted central catheter biomaterial design and antibiotic therapy had no significant impact on microbial communities. However, the diversity of microbial communities significantly decreased with dwell time.

CONCLUSION

More diverse pathogens were present on the colonised peripherally inserted central catheter collected from the patient with central line-associated bloodstream infection. Microbial biofilm composition did not appear to be affected by the design of peripherally inserted central catheter biomaterials or antibiotic therapy. However, the diversity of the microbial communities appeared to decrease with dwell time.

Perceptions of risk factors for phlebitis among Malaysian nurses

BACKGROUND

Intravenous therapy is an integral part of professional nursing practice. Nurses have a responsibility to recognise risk factors for phlebitis.

AIMS

To investigate nurses' perceptions of risk factors for phlebitis in a tertiary teaching hospital in north-east Peninsular Malaysia.

METHODS

A cross-sectional study of 199 randomly selected nurses were surveyed for their perceptions of risk factors for phlebitis using a self-administered questionnaire.

FINDINGS

More than half of the nurses (56.8%) had a good perception levels of risk factors for phlebitis. There was a significant association between the clinical area and nurses' perceptions of risk factors for phlebitis (p=0.04). Nurses working in medical, orthopaedic, and surgical areas had slightly better perceptions than nurses working in multidisciplinary and oncology areas.

CONCLUSION

These findings suggest that nurses need to continually improve their knowledge about risk factors for phlebitis to ensure safer nursing practice.

Skin colonization at peripheral intravenous catheter insertion sites increases the risk of catheter colonization and infection

BACKGROUND

Peripheral intravenous catheters (PIVCs) break the skin barrier, and preinsertion antiseptic disinfection and sterile dressings are used to reduce risk of catheter-related bloodstream infection (CRBSI). In this study, the impact of PIVC skin site colonization on tip colonization and the development of CRBSI was investigated.

METHODS

A total of 137 patients' PIVC skin site swabs and paired PIVC tips were collected at catheter removal, cultured, and bacterial species and clonality were identified.

RESULTS

Of 137 patients, 45 (33%) had colonized skin sites and/or PIVC tips. Of 16 patients with paired colonization of both the skin site and PIVC tips, 11 (69%) were colonized with the same bacterial species. Of these, 77% were clonally related, including 1 identical clone of Pseudomonas aeruginosa in a patient with systemic infection and the same organism identified in blood culture.

CONCLUSIONS

The results demonstrate that opportunistic pathogen colonization at the skin site poses a significant risk for PIVC colonization and CRBSI. Further research is needed to improve current preinsertion antiseptic disinfection of PIVC skin site and the sterile insertion procedure to potentially reduce PIVC colonization and infection risk.

Bacterial biofilm formation on implantable devices and approaches to its treatment and prevention

In living organisms, biofilms are defined as complex communities of bacteria residing within an exopolysaccharide matrix that adheres to a surface. In the clinic, they are typically the cause of chronic, nosocomial, and medical device-related infections. Due to the antibiotic-resistant nature of biofilms, the use of antibiotics alone is ineffective for treating biofilm-related infections. In this review, we present a brief overview of concepts of bacterial biofilm formation, and current state-of-the-art therapeutic approaches for preventing and treating biofilms. Also, we have reviewed the prevalence of such infections on medical devices and discussed the future challenges that need to be overcome in order to successfully treat biofilms using the novel technologies being developed.

Taurolidine-citrate-heparin lock reduces catheter-related bloodstream infections in intestinal failure patients dependent on home parenteral support: a randomized, placebo-controlled trial

Background: In patients with intestinal failure who are receiving home parenteral support (HPS), catheter-related bloodstream infections (CRBSIs) inflict health impairment and high costs.Objective: This study investigates the efficacy and safety of the antimicrobial catheter lock solution, taurolidine-citrate-heparin, compared with heparin 100 IE/mL on CRBSI occurrence.Design: Forty-one high-risk patients receiving HPS followed in a tertiary HPS unit were randomly assigned in a double-blinded, placebo-controlled trial. External, stratified randomization was performed according to age, sex, and prior CRBSI incidence. The prior CRBSI incidence in the study population was 2.4 episodes/1000 central venous catheter (CVC) days [95% Poisson confidence limits (CLs): 2.12, 2.71 episodes/1000 CVC days]. The maximum treatment period was 2 y or until occurrence of a CRBSI or right-censoring because of CVC removal. The exact permutation tests were used to calculate P values for the log-rank tests.Results: Twenty patients received the taurolidine-citrate-heparin lock and 21 received the heparin lock, with 9622 and 6956 treatment days, respectively. In the taurolidine-citrate-heparin arm, no CRBSIs occurred, whereas 7 CRBSIs occurred in the heparin arm, with an incidence of 1.0/1000 CVC days (95% Poisson CLs: 0.4, 2.07/1000 CVC days; P = 0.005). The CVC removal rates were 0.52/1000 CVC days (95% Poisson CLs: 0.17, 1.21/1000 CVC days) and 1.72/1000 CVC days (95% Poisson CLs: 0.89, 3.0/1000 CVC days) in the taurolidine-citrate-heparin and heparin arm, respectively, tending to prolong CVC survival in the taurolidine arm (P = 0.06). Costs per treatment year were lower in the taurolidine arm (€2348) than in the heparin arm (€6744) owing to fewer admission days related to treating CVC-related complications (P = 0.02).Conclusions: In patients with intestinal failure who are life dependent on HPS, the taurolidine-citrate-heparin catheter lock demonstrates a clinically substantial and cost-beneficial reduction of CRBSI occurrence in a high-risk population compared with heparin. This trial was registered at clinicaltrials.gov as NCT01948245.

Inhibition of bacterial adhesion and biofilm formation by dual functional textured and nitric oxide releasing surfaces

In separate prior studies, physical topographic surface modification or nitric oxide (NO) release has been demonstrated to each be an effective approach to inhibit and control bacterial adhesion and biofilm formation on polymeric surfaces. Such approaches can prevent biomaterial-associated infection without causing the antibiotic resistance of the strain. In this work, both techniques were successfully integrated and applied to a polyurethane (PU) biomaterial surface that bears ordered pillar topographies (400/400nm and 500/500nm patterns) at the top surface and a S-nitroso-N-acetylpenicillamine (SNAP, NO donor) doped sub-layer in the middle, via a soft lithography two-stage replication process. Upon placing the SNAP textured PU films into PBS at 37°C, the decomposition of SNAP within polymer film initiates NO release with a lifetime of up to 10days at flux levels >0.5×10^-10molmin^-1cm^-2 for a textured polyurethane layer containing 15wt% SNAP. The textured surface reduces the accessible surface area and the opportunity of bacteria-surface interaction, while the NO release from the same surface further inhibits bacterial growth and biofilm formation. Such dual functionality surfaces are shown to provide a synergistic effect on inhibition of Staphylococcus epidermidis bacterial adhesion that is significantly greater than the inhibition of bacterial adhesion achieved by either single treatment approach alone. Longer term experiments to observe biofilm formation demonstrate that the SNAP doped-textured PU surface can inhibit the biofilm formation for >28d and provide a practical approach to improve the biocompatibility of current biomimetic biomaterials and thereby reduce the risk of pathogenic infection.

STATEMENT OF SIGNIFICANCE

Microbial infection remains a significant barrier to development and implementation of advanced blood-contacting medical devices. Clearly, determining how to design and control material properties that can reduce microbial infection is a central question to biomaterial researchers. In separate prior studies, physical topographic surface modification or nitric oxide (NO) release has been demonstrated to each be an effective approach to inhibit and control bacterial adhesion and biofilm formation on polymeric surfaces. Such approaches can prevent biomaterial-associated infection without causing antibiotic resistance of the bacterial strain. However, efficiency of antimicrobial properties of each approach is still limited and far from sufficient for widespread clinical use. This work successfully integrates both techniques and applies them to a polyurethane (PU) biomaterial surface that bears dual functions, surface topographic modification and NO release. The former reduces the surface contact area and changes surface wettability, resulting in reduction of bacterial adhesion, and NO release further inhibits bacteria growth. Such dual functionalized surfaces provide a synergistic effect on inhibition of Staphylococcus epidermidis bacterial adhesion that is significantly greater than the inhibition of bacterial adhesion achieved by either single treatment approach alone. Furthermore, longer-term experiments demonstrate that the dual functionalized surfaces can inhibit biofilm formation for >28days. The success of this work provides a practical approach to improve the biocompatibility of current biomaterials and thereby reduce the risk of pathogenic infection.

Non-culture based diagnostics for intravascular catheter related bloodstream infections

INTRODUCTION

intravascular catheter related bloodstream infection (IVC-BSI) is a leading cause of nosocomial infections and associated with significant morbidity and mortality. Early detection and adequate treatment of causative pathogens is critical for a favourable outcome. However, it takes significant time to receive microbiological results due to the current reference diagnostic method's reliance on microbial growth. Areas covered: This review discusses culture and non-culture based techniques for the diagnosis of non IVC-BSI and IVC-BSI, including molecular methods and biomarkers. Different diagnostic strategies are evaluated and the potential of new generation of diagnostic assays highlighted. Expert commentary: The development of additional diagnostic methods has potential to beneficially supplement conventional culture diagnosis, and molecular techniques have particular potential to fulfil this need. They would also contribute significant new knowledge on the bacterial species present on catheters that are generally missed by diagnosis using traditionally culture-dependent methods. Advances in molecular strategies, together with new biomarkers, might lead to the development of faster, more sensitive and cheaper technologies and instruments. This review aims to provide a platform for the further development of IVCBSI diagnostic techniques.

Infection risks associated with peripheral vascular catheters

BACKGROUND

Peripheral vascular catheters (PVC) are the most frequently used invasive medical devices in hospitals, with 330 million sold each year in the USA alone. One in three UK inpatients at any one time has at least one PVC in situ according to the Scottish National Prevalence survey.

METHOD

A narrative review of studies describing the infection risks associated with PVCs.

RESULTS

It is estimated that 30-80% of hospitalised patients receive at least one PVC during their hospital stay. Despite their prevalence, PVCs are not benign devices, and the high number of PVCs inserted annually has resulted in serious catheter-related bloodstream infections and significant morbidity, prolonged hospital stay and increased healthcare system costs. To date, PVC infections have been under-evaluated. Most studies focus on central venous catheter rather than PVC-associated bloodstream infections. Risks associated with PVC infection must be addressed to reduce patient morbidity and associated costs of prolonged hospital admission and treatment.

DISCUSSION

This article discusses the sources and routes of PVC-associated infection and outlines known effective prevention and intervention strategies.

A comparison of two methods of treatment for central catheter tunnel phlegmon in home parenteral nutrition patients

INTRODUCTION

The ESPEN guidelines on long-term (> 3 months) parenteral nutrition recommend the use of tunnelled central venous catheters (CVCs) to minimise the risk of insertion site infection. A developed symptomatic infection of the soft tissue tunnel surrounding a CVC may rapidly become directly life threatening if the infection progresses along the catheter tunnel towards its end inserted into the venous system. This requires immediate management to eliminate infection and limit its effects.

AIM

To compare two surgical techniques for the treatment of suppurative inflammation of a CVC tunnel: conventional drainage of the infected tissues (surgical technique A) vs. radical en bloc excision of the infected tissues together with the infected central catheter (surgical technique B).

MATERIAL AND METHODS

Seventy-three patients hospitalised due to CVC tunnel phlegmon between April 2004 and May 2014 were included in the retrospective study. Thirty-four (46.5%) patients underwent surgical procedure A and another 39 (53.5%) underwent procedure B.

RESULTS

The mean duration of antibiotic therapy following procedure A was 8 ±3 days, whereas procedure B required 7 ±2 days of antibiotic therapy (NS). The mean hospitalisation period following procedure B was over 8 days shorter in comparison to that following procedure A (16.54 ±7.59 vs. 24.87 ±10.19, p = 0.009, respectively).

CONCLUSIONS

The surgical treatment of CVC tunnel phlegmon involving radical en bloc excision of suppurated tissues along with the infected CVC shortens hospitalisation, expedites the insertion of a new CVC, and potentially reduces treatment costs.

Microbial biofilms associated with intravascular catheter-related bloodstream infections in adult intensive care patients

Catheter-related bloodstream infection (CRBSI) is one of the most serious complications in hospitalised patients, leading to increased hospitalisation, intensive care admissions, extensive antibiotic treatment and mortality. A greater understanding of these bacterial infections is needed to improve the prevention and the management of CRBSIs. We describe here the systematic culture-independent evaluation of intravascular catheter (IVC) bacteriology. Twelve IVCs (6 central venous catheters and 6 arterial catheters) were collected from 6 patients. By using traditional culture methods, 3 patients were diagnosed with catheter colonisation including 1 patient who also had CRBSI, and 3 had no colonisation. From a total of 839,539 high-quality sequence reads from high-throughput sequencing, 8 microbial phyla and 76 diverse microbial genera were detected. All IVCs examined in this study were colonised with complex microbial communities including "non-colonised IVCs," as defined using traditional culture methods. Two main community types were observed: Enterobacteriaceae spp., dominant in patients without colonisation or CRBSI; and Staphylococcus spp., dominant in patients with colonisation and CRBSI. More diverse pathogens and a higher microbial diversity were present in patients with IVC colonisation and CRBSI. Community composition did not appear to be affected by patients' antibiotic treatment or IVC type. Characterisation of these communities is the first step in elucidating roles of these pathogens in disease progression, and to ultimately facilitate the improved prevention, refined diagnosis and management of CRBSI.

Staphylococcus epidermidis as a cause of bacteremia

Staphylococcus epidermidis is a biofilm-producing commensal organism found ubiquitously on human skin and mucous membranes, as well as on animals and in the environment. Biofilm formation enables this organism to evade the host immune system. Colonization of percutaneous devices or implanted medical devices allows bacteria access to the bloodstream. Isolation of this organism from blood cultures may represent either contamination during the blood collection procedure or true bacteremia. S. epidermidis bloodstream infections may be indolent compared with other bacteria. Isolation of S. epidermidis from a blood culture may present a management quandary for clinicians. Over-treatment may lead to patient harm and increases in healthcare costs. There are numerous reports indicating the difficulty of predicting clinical infection in patients with positive blood cultures with this organism. No reliable phenotypic or genotypic algorithms currently exist to predict the pathogenicity of a S. epidermidis bloodstream infection. This review will discuss the latest advances in identification methods, global population structure, pathogenicity, biofilm formation, antimicrobial resistance and clinical significance of the detection of S. epidermidis in blood cultures. Previous studies that have attempted to discriminate between invasive and contaminating strains of S. epidermidis in blood cultures will be analyzed.

Microbial diversity on intravascular catheters from paediatric patients

Microorganisms play important roles in intravascular catheter (IVC)-related infections, which are the most serious complications in children with IVCs, leading to increased hospitalisation, intensive care admissions, extensive antibiotic treatment and mortality. A greater understanding of bacterial communities is needed in order to improve the management of infections. We describe here the systematic culture-independent evaluation of IVC bacteriology in IVC biofilms. Twenty-four IVC samples (six peripherally inserted central catheters, eight central venous catheters and ten arterial catheters) were collected from 24 paediatric patients aged 0 to 14 years old. Barcoded amplicon libraries produced from genes coding 16S rRNA and roll-plate culture methods were used to determine the microbial composition of these samples. From a total of 1,043,406 high-quality sequence reads, eight microbial phyla and 136 diverse microbial genera were detected, separated into 12,224 operational taxonomic units (OTUs). Three phyla (Actinobacteria, Firmicutes and Proteobacteria) predominate the microorganism on the IVC surfaces, with Firmicutes representing nearly half of the OTUs found. Among the Firmicutes, Staphylococcus (15.0% of 16S rRNA reads), Streptococcus (9.6%) and Bacillus (6.1%) were the most common. Community composition did not appear to be affected by patients' age, gender, antibiotic treatment or IVC type. Differences in IVC microbiota were more likely associated with events arising from catheter dwell time, rather than the type of IVC used.

Surface functionalization by covalent immobilization of an innovative carvacrol derivative to avoid fungal biofilm formation

Carvacrol, an aromatic terpenic compound, known to be antimicrobial was grafted onto gold surfaces via two strategies based on newly-synthesized cross-linkers involving either an ester bond which can be cleaved by microbial esterases, or a covalent ether link. Surface functionalizations were characterized at each step by reflection absorption infrared spectroscopy (RAIRS). The two functionalized gold samples both led to a loss of culturability of the yeast Candida albicans, higher than 65%, indicating that the activity of the freshly-designed surfaces was probably due to still covalently immobilized carvacrol. On the contrary, when a phenyl group replaced the terpenic moiety, the yeast culturability increased by about 30%, highlighting the specific activity of carvacrol grafted on the surfaces. Confocal microscopy analyses showed that the mode of action of the functionalized surfaces with the ester or the ether of carvacrol was, in both cases, fungicidal and not anti-adhesive. Finally, this study shows that covalently immobilization of terpenic compounds can be used to design promising antimicrobial surfaces.

Investigation of biofilm formation on a charged intravenous catheter relative to that on a similar but uncharged catheter

Catheter-related blood stream infections increase morbidity, mortality, and costs. This study investigated whether Certofix^® protect antimicrobial catheters carry a surface charge and whether this inhibits biofilm formation. The capacitance of the catheter surfaces was measured and, to determine if the catheters released ions, distilled water was passed through and current measured as a function of voltage. With probes touching the inner and outer surfaces, capacitance was not voltage-dependent, indicating surfaces were uncharged or carried a similar charge. When one probe penetrated the catheter wall, capacitance was weakly voltage-dependent, indicating the presence of a surface charge. Standard and charged catheters were also exposed to phosphate buffered saline as controls or 2×10⁶ colony forming units/mL (in phosphate buffered saline) of six different microorganisms for 60 or 120 minutes. When the growth of detached bacteria was measured, biofilm formation was significantly reduced, (P<0.05), for charged catheters for all organisms.

Microbiocidal effects of various taurolidine containing catheter lock solutions

BACKGROUND & AIMS

We have recently shown that a catheter lock solution containing taurolidine dramatically decreases catheter-related bloodstream infections (CRBSI) in patients on home parenteral nutrition (HPN) when compared to heparin. Since several taurolidine formulations are commercially available, some of which also contain citrate or heparin, we were interested in the effect of these different locks on growth and biofilm formation of fungal, Gram-negative and Gram-positive pathogens that are known to impede HPN treatment.

METHODS

Clinical isolates obtained during CRBSI of HPN patients were grown in the presence of catheter locks (2% taurolidine, 1.34% taurolidine-citrate, 1.34% taurolidine-citrate-heparin, citrate and heparin) or phosphate buffered saline diluted in lysogeny broth medium for bacteria and sabouraud liquid medium for yeasts. Biofilm formation, assessed by crystal violet staining, and growth of clinical isolates were determined by optical density measurements.

RESULTS

We found that 12.5× diluted solutions of all taurolidine containing formulations completely prevented growth of Escherichia coli, Staphylococcus aureus and Candida glabrata. Growth of these microbes was detected earlier in 1.34% taurolidine-citrate(-heparin) than in 2% taurolidine, while citrate and heparin did not inhibit growth of clinical isolates compared to PBS. No differences in biofilm formation were found between taurolidine containing solutions.

CONCLUSION

Taurolidine containing lock solutions prevent growth of fungal, Gram-negative and Gram-positive pathogens. While 2% taurolidine appears to be the most potent in this respect in this in vitro setting, the relevance of the small differences in growth inhibition between the commercially available taurolidine containing lock solutions for clinical practice remains to be established.

Implementing tissue engineering and regenerative medicine solutions in medical implants

BACKGROUND

Surgical implants are widely used in the medical field but their long-term performance is limited due to failure of integration with tissues. This manuscript describes very well-known problems associated with implants and discusses novel solutions used in tissue engineering and regenerative medicine that can be implemented in this uncommonly discussed medical area.

SOURCES OF DATA

General and medical literature describing modifications of medical and surgical implants, biofunctionalization, tissue engineering and regenerative medicine.

AREAS OF AGREEMENT

Procedures for surgical implantation have grown substantially in the last few decades and provided improved quality of life for patients, regardless of area of implantation and device type and purpose.

AREAS OF CONTROVERSY

In general, implants fail because of lack of long-term integration with the surrounding tissues. Implant manufacturers have not addressed implant failure from the point of view of biointegration. In addition, some medical practitioners are inclined to treat implant failure by using anti-infection methods to prevent bacterial adhesion. However, both approaches are conceptually limited, as discussed in this manuscript.

GROWING POINTS

Implantation in the future will not be limited to medically needed procedures but also to a growing number of cosmetic body transformation procedures, which may include perceived 'improved implant functions' over natural tissues or organs. An additional trend is that implant procedures are being progressively performed in younger individuals.

AREAS TIMELY FOR DEVELOPING RESEARCH

Current implants generally do not allow the physician to have controlled long-term access to internal tissues in contact with the implants, for example to release specific compounds when medically needed to the problem area.

Nanostructuring carbon fibre probes for use in central venous catheters

A carbon fibre probe is described which utilises the oxidation of an endogenous biomarker to provide diagnostic information on the condition of intravascular access lines. The probe surface was modified through anodic oxidation to provide a high selectivity towards urate which was used as a redox probe through which the pH could be determined. A Nernstian response (-60 mV/pH) was obtained which was free from the interference of other redox species common to biofluids. The electroanalytical performance of the probe has been optimised and the applicability of the approach demonstrated through testing the responses in whole blood.

Reducing the risk of infection associated with vascular access devices through nanotechnology: a perspective

Intravascular catheter-related infections are still a major problem in health care and are associated with significant morbidity, mortality, and additional cost. The formation of microbial biofilm on catheters makes these infections particularly complicated, as microbial cells that detach from the biofilm can lead to infection, and because these microorganisms are highly resistant to many antimicrobial agents; thus, catheter removal is often required to successfully treat infection. To reduce the risks of catheter-related infections, many strategies have been applied, such as improvements in aseptic insertion and post-insertion care practices, implantation techniques, and antibiotic coated or impregnated materials. However, despite significant advances in using these methods, it has not been possible to completely eradicate biofilm infections. Currently, nanotechnology approaches seem to be among the most promising for preventing biofilm formation and resultant catheter-related bloodstream infection (especially with multi-resistant bacterial strains). In this review, current knowledge about catheter technology and design, the mechanisms of catheter-related bloodstream infection, and the insertion and care practices performed by medical staff, are discussed, along with novel, achievable approaches to infection prevention, based on nanotechnology.

Plasma-polyplumbagin-modified microfiber probes: a functional material approach to monitoring vascular access line contamination

Atmospheric plasma treated carbon fiber filaments (10 micrometer) were used as the base substrate in the design of a probe intended for use within intravascular access devices. The microfiber probe was further functionalized with a polyplumbagin layer through which the line pH could be determined voltammetrically and therein provide the potential for obtaining diagnostic information relating to bacterial colonization of the line. The redox processes attributed to the immobilized polymer are characterized and a methodology developed to enable the acquisition of a redox signal that is selective and sensitive to pH. The applicability of the composite probe was demonstrated through examining the direct response in whole blood.

Peripherally inserted central catheters in infants and children - indications, techniques, complications and clinical recommendations

Venous access required both for blood sampling and for the delivery of medicines and nutrition is an integral element in the care of sick infants and children. Peripherally inserted central catheters (PICCs) have been shown to be a valuable alternative to traditional central venous devices in adults and neonates. However, the evidence may not extrapolate directly to older paediatric patients. In this study, we therefore review the indications, methods of insertion and complications of PICC lines for children beyond the neonatal age to provide clinical recommendations based on a search of the current literature. Although the literature is heterogeneous with few randomised studies, PICCs emerge as a safe and valuable option for intermediate- to long-term central venous access in children both in and out of hospital. Insertion can often be performed in light or no sedation, with little risk of perioperative complications. Assisted visualisation, preferably with ultrasound, yields high rates of insertion success. With good catheter care, rates of mechanical, infectious and thrombotic complications are low and compare favourably with those of traditional central venous catheters. Even in the case of occlusion or infection, fibrinolytics and antibiotic locks often allow the catheter to be retained.

Colonization of peripheral intravascular catheters with biofilm producing microbes: Evaluation of risk factors

BACKGROUND

Biofilms often colonize catheters and contribute to catheter-related septicemia. However, predictors of catheter colonization by biofilms remain poorly defined. The aim of this study was to evaluate clinical factors that may be associated with biofilm colonization of catheters.

MATERIALS AND METHODS

A total of 54 isolates colonizing the peripheral intravascular catheters (IVCs) were studied and their biofilm production ability was analyzed by the tube method and antimicrobial susceptibility was also done. A detailed clinical history and examination was done of each subject to know age, sex, duration of use of IVCs, site of IVCs, swelling/purulence around the IVCs, number of attempts to install the catheter, and duration of hospital stay.

RESULTS

44 (81.4%) out of 54 isolates colonizing the catheters showed biofilm formation. Biofilm formations were significantly associated with duration of hospital stay of more than 7 days [odds ratio (OR) = 6.6; 95% confidence interval (CI) = 1.3-34; P value (P) = 0.02], multiple attempts to install the catheter (OR=7; CI=1.5-31.8; P=0.01), and multidrug resistance (OR=9.5; CI=1.8 - 51.1: P=0.008). Klebsiella pneumoniae and Candida spp. comprised most of the biofilm-producing isolates. The overall susceptibility to antimicrobials was low among biofilm-producing compared to nonbiofilm-producing microbes.

CONCLUSION

The results of this study suggest that evaluation of predictors of biofilm production is important in order to understand, prevent or manage biofilm colonization of IVCs.

Routine versus clinically indicated replacement of peripheral intravenous catheters: a randomised controlled equivalence trial

BACKGROUND

The millions of peripheral intravenous catheters used each year are recommended for 72-96 h replacement in adults. This routine replacement increases health-care costs and staff workload and requires patients to undergo repeated invasive procedures. The effectiveness of the practice is not well established. Our hypothesis was that clinically indicated catheter replacement is of equal benefit to routine replacement.

METHODS

This multicentre, randomised, non-blinded equivalence trial recruited adults (≥18 years) with an intravenous catheter of expected use longer than 4 days from three hospitals in Queensland, Australia, between May 20, 2008, and Sept 9, 2009. Computer-generated random assignment (1:1 ratio, no blocking, stratified by hospital, concealed before allocation) was to clinically indicated replacement, or third daily routine replacement. Patients, clinical staff, and research nurses could not be masked after treatment allocation because of the nature of the intervention. The primary outcome was phlebitis during catheterisation or within 48 h after removal. The equivalence margin was set at 3%. Primary analysis was by intention to treat. Secondary endpoints were catheter-related bloodstream and local infections, all bloodstream infections, catheter tip colonisation, infusion failure, catheter numbers used, therapy duration, mortality, and costs. This trial is registered with the Australian New Zealand Clinical Trials Registry, number ACTRN12608000445370.

FINDINGS

All 3283 patients randomised (5907 catheters) were included in our analysis (1593 clinically indicated; 1690 routine replacement). Mean dwell time for catheters in situ on day 3 was 99 h (SD 54) when replaced as clinically indicated and 70 h (13) when routinely replaced. Phlebitis occurred in 114 of 1593 (7%) patients in the clinically indicated group and in 114 of 1690 (7%) patients in the routine replacement group, an absolute risk difference of 0·41% (95% CI -1·33 to 2·15%), which was within the prespecified 3% equivalence margin. No serious adverse events related to study interventions occurred.

INTERPRETATION

Peripheral intravenous catheters can be removed as clinically indicated; this policy will avoid millions of catheter insertions, associated discomfort, and substantial costs in both equipment and staff workload. Ongoing close monitoring should continue with timely treatment cessation and prompt removal for complications.

FUNDING

Australian National Health and Medical Research Council.

Ultrastructure of a novel bacterial form located in Staphylococcus aureus in vitro and in vivo catheter-associated biofilms

Bacterial biofilms are ubiquitous in nature, industry, and medicine, and understanding their development and cellular structure is critical in controlling the unwanted consequences of biofilm growth. Here, we report the ultrastructure of a novel bacterial form observed by scanning electron microscopy in the luminal vegetations of catheters from patients with active Staphylococcus aureus bacteremia. This novel structure had the general appearance of a normal staphylococcal cell but up to 10 to 15 times as large. Transmission electron microscopy indicated that these structures appeared as sacs enclosing multiple normal-sized (~0.6 µm) staphylococcal forms. Using in vitro cultivated biofilms, cytochemical studies using fluorescent reagents revealed that these structures were rich in lipids and appeared within 15 min after S. aureus inoculation onto clinically relevant abiotic surfaces. Because they appeared early in biofilm development, these novel bacterial forms may represent an unappreciated mechanism for biofilm surface adherence, and their prominent lipid expression levels could explain the perplexing increased antimicrobial resistance of biofilm-associated bacteria.

An organoselenium compound inhibits Staphylococcus aureus biofilms on hemodialysis catheters in vivo

Colonization of central venous catheters (CVCs) by pathogenic bacteria leads to catheter-related bloodstream infections (CRBSIs). These colonizing bacteria form highly antibiotic-resistant biofilms. Staphylococcus aureus is one of the most frequently isolated pathogens in CRBSIs. Impregnating CVC surfaces with antimicrobial agents has various degrees of effectiveness in reducing the incidence of CRBSIs. We recently showed that organoselenium covalently attached to disks as an antibiofilm agent inhibited the development of S. aureus biofilms. In this study, we investigated the ability of an organoselenium coating on hemodialysis catheters (HDCs) to inhibit S. aureus biofilms in vitro and in vivo. S. aureus failed to develop biofilms on HDCs coated with selenocyanatodiacetic acid (SCAA) in either static or flowthrough continuous-culture systems. The SCAA coating also inhibited the development of S. aureus biofilms on HDCs in vivo for 3 days. The SCAA coating was stable and nontoxic to cell culture or animals. This new method for coating the internal and external surfaces of HDCs with SCAA has the potential to prevent catheter-related infections due to S. aureus.