Vascular Catheter-Related Infection and Sepsis

A review on antimicrobial strategies in mitigating biofilm-associated infections on medical implants

Biomedical implants are crucial in providing support and functionality to patients with missing or defective body parts. However, implants carry an inherent risk of bacterial infections that are biofilm-associated and lead to significant complications. These infections often result in implant failure, requiring replacement by surgical restoration. Given these complications, it is crucial to study the biofilm formation mechanism on various biomedical implants that will help prevent implant failures. Therefore, this comprehensive review explores various types of implants (e.g., dental implant, orthopedic implant, tracheal stent, breast implant, central venous catheter, cochlear implant, urinary catheter, intraocular lens, and heart valve) and medical devices (hemodialyzer and pacemaker) in use. In addition, the mechanism of biofilm formation on those implants, and their pathogenesis were discussed. Furthermore, this article critically reviews various approaches in combating implant-associated infections, with a special emphasis on novel non-antibiotic alternatives to mitigate biofilm infections.

Clostridioides difficile Biofilm

Clostridioides difficile infection (CDI), previously Clostridium difficile infection, is a symptomatic infection of the large intestine caused by the spore-forming anaerobic, gram-positive bacterium Clostridioides difficile. CDI is an important healthcare-associated disease worldwide, characterized by high levels of recurrence, morbidity, and mortality. CDI is observed at a higher rate in immunocompromised patients after antimicrobial therapy, with antibiotics disrupting the commensal microbiota and promoting C. difficile colonization of the gastrointestinal tract.A rise in clinical isolates resistant to multiple antibiotics and the reduced susceptibility to the most commonly used antibiotic molecules have made the treatment of CDI more complicated, allowing the persistence of C. difficile in the intestinal environment.Gut colonization and biofilm formation have been suggested to contribute to the pathogenesis and persistence of C. difficile. In fact, biofilm growth is considered as a serious threat because of the related antimicrobial tolerance that makes antibiotic therapy often ineffective. This is the reason why the involvement of C. difficile biofilm in the pathogenesis and recurrence of CDI is attracting more and more interest, and the mechanisms underlying biofilm formation of C. difficile as well as the role of biofilm in CDI are increasingly being studied by researchers in the field.Findings on C. difficile biofilm, possible implications in CDI pathogenesis and treatment, efficacy of currently available antibiotics in treating biofilm-forming C. difficile strains, and some antimicrobial alternatives under investigation will be discussed here.

Thermoplastic polyurethane surface coated with polymer brushes for reduced protein and cell attachment

The objective of this study was to coat negatively charged polymer brushes covalently onto the surface of thermoplastic polyurethane (TPU) using a simple conventional surface free-radical polymerization technique. The coated surfaces were assessed with contact angle, protein adsorption, cell adhesion and bacterial adhesion. Bovine serum albumin (BSA) and bovine fibrinogen (BFG) were used for protein adsorption evaluation. Mouse fibroblasts (NIH-3T3) and Pseudomonas aeruginosa (P. aeruginosa) were used to assess surface adhesion. Results show that the TPU surface modified with the attached polymer brushes exhibited significantly reduced contact angle, protein adsorption, and cell as well as bacterial adhesion, among which the negatively charged polymers showed the extremely low values in all the tests. Its contact angle is 5°, as compared to 70° for original TPU. Its BSA, BFG, 3T3 adhesion and P. aeruginosa adhesion were 93%, 84%, 92%, and 93% lower than original TPU. Furthermore, the TPU surface coated with negatively charged polymer brushes exhibited a hydrogel-like property. The results indicate that placing acrylic acids using a simple surface-initiated free-radical polymerization onto a TPU surface and then converting those to negative charges can be an effective and efficient route for fouling resistant applications.

3D-printed biosurfactant-chitosan antibacterial coating for the prevention of silicone-based associated infections

Infections associated with the surfaces of medical devices represent a critical problem due to biofilm formation and the growing resistance towards antibacterial drugs. This is particularly relevant in commonly used invasive devices such as silicone-based ones where a demand for alternative antibiofilm surfaces is increasing. In this work, an antimicrobial chitosan-biosurfactant hydrogel mesh was produced by 3D-printing. The 3D structure was designed to coat polydimethylsiloxane-based medical devices for infection prevention. Additionally, the porous 3D structure allows the incorporation of customized bioactive components. For this purpose, two biosurfactants (surfactin and sophorolipids) were biosynthesized and tested for their antimicrobial activity. In addition, the printing of surfactant-chitosan-based coatings was optimized, and the resulting 3D structures were characterized (i.e., wettability, FTIR-ATR, antimicrobial activity, and biocompatibility). Compared with surfactin, the results showed a better yield and higher antibacterial activity against Gram-positive bacteria for sophorolipids (SLs). Thus, SLs were used to produce chitosan-based 3D-printed coatings. Overall, the SLs-impregnated coatings showed the best antibacterial activity against Staphylococcus aureus planktonic bacteria (61 % of growth inhibition) and antibiofilm activity (2 log units reduction) when compared to control. Furthermore, concerning biocompatibility, the coatings were cytocompatible towards human dermal fibroblasts. Finally, the coating presented a mesh suitable to be filled with a model bioactive compound (i.e., hyaluronic acid), paving the way to be used for customized therapeutics.

Polyvinylchloride surface with enhanced cell/bacterial adhesion-resistant and antibacterial functions

This study reports synthesis and attachment of a novel antibacterial and hydrophilic polymer onto a polyvinylchloride surface via a simple and mild surface coating technique. The compound 3,4-dichloro-5-hydroxy-2(5H)-furanone was derivatized and copolymerized with N-vinylpyrrolidone. The copolymer was then covalently coated onto polyvinylchloride surface. 3T3 mouse fibroblast cells and bacterium Pseudomonas aeruginosa were used to evaluate surface adhesion and antibacterial activity. Results showed that the polymer-modified polyvinylchloride surface not only exhibited significantly decreased 3T3 fibroblast cell adhesion with a 64–84% reduction but also demonstrated significantly decreased P. aeruginosa adhesion with a 65–84% reduction, as compared to unmodified polyvinylchloride. Furthermore, the modified polyvinylchloride surfaces exhibited significant antibacterial functions by inhibiting P. aeruginosa growth with a 58–80% reduction and killing bacteria, as compared to unmodified polyvinylchloride. These results demonstrate that covalent polymer attachment conferred cell/bacterial adhesion-resistant and antibacterial properties to the polyvinylchloride surface.

Surface modification of polyurethane with a hydrophilic, antibacterial polymer for improved antifouling and antibacterial function

Antimicrobial surface is important for the inhibition of bacteria or biofilm formation on biomaterials. The objective of this study was to immobilize a novel hydrophilic polymer containing the antibacterial moiety onto polyurethane surface via a simple surface coating technology to make the surface not only antibacterial but also antifouling. The compound 3,4-dichloro-5-hydroxy-2(5H)-furanone was derivatized, characterized and incorporated onto polyvinylpyrrolidone containing succinimidyl functional groups, followed by coating onto the polyurethane surface. Contact angle, antibacterial function and protein adsorption of the modified surface were evaluated. The result shows that the modified surface exhibited significantly enhanced hydrophilicity with a 54-65% decrease in contact angle, increased antibacterial activity to Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa with a 24-57% decrease in viability, and reduced human serum albumin adsorption with a 64-70% decrease in adsorption, as compared to the original polyurethane.

Healthcare-associated infections, medical devices and biofilms: risk, tolerance and control

Biofilms are of great importance in infection control and healthcare-associated infections owing to their inherent tolerance and 'resistance' to antimicrobial therapies. Biofilms have been shown to develop on medical device surfaces, and dispersal of single and clustered cells implies a significant risk of microbial dissemination within the host and increased risk of infection. Although routine microbiological testing assists with the diagnosis of a clinical infection, there is no 'gold standard' available to reveal the presence of microbial biofilm from samples collected within clinical settings. Furthermore, such limiting factors as viable but non-culturable micro-organisms and small-colony variants often prevent successful detection. In order to increase the chances of detection and provide a more accurate diagnosis, a combination of microbiological culture techniques and molecular methods should be employed. Measures such as antimicrobial coating and surface alterations of medical devices provide promising opportunities in the prevention of biofilm formation on medical devices.

In vitro activity and durability of a combination of an antibiofilm and an antibiotic against vascular catheter colonization

Catheter-associated infections can cause severe complications and even death. Effective antimicrobial modification of catheters that can prevent device colonization has the potential of preventing clinical infection. We studied in vitro the antimicrobial activities of central venous catheters impregnated with N-acetylcysteine (NAC), an antibiofilm agent, and a broad-spectrum antibiotic against a range of important clinical pathogens. NAC-levofloxacin-impregnated (NACLEV) catheters were also evaluated for their antiadherence activity. NACLEV catheters produced the most active and durable antimicrobial effect against both Gram-positive and Gram-negative isolates and significantly reduced colonization (P < 0.0001) by all tested pathogens compared to control catheters. These in vitro results suggest that this antimicrobial combination can potentially be used to combat catheter colonization and catheter-associated infection.

Analysis: continuous glucose monitoring in the intensive care unit

Control of glycemia in hospitalized patients is important; hypoglycemia is associated with increased mortality, and hyperglycemia is associated with adverse outcomes. For these reasons, though no such device is currently available, continuous glucose monitoring (CGM) is an attractive option, especially in the critical care setting. Schierenbeck and coauthors, in this issue of Journal of Diabetes Science and Technology, report on the use of a specialized central catheter designed to monitor glucose continuously in post cardiac surgery patients. This catheter, which was indwelled within the great veins, was specially designed with a separate lumen and membrane that allowed continuous glucose microdialysis. Accuracy was quite good, better than has been reported with the use of commercially-available CGM devices. Ideally, further development of this quite promising catheter-based device would allow it to be used also to deliver fluids and drugs, thus avoiding the need for a second catheter elsewhere.

Candida spp. isolated from inpatients, the environment, and health practitioners in the Pediatric Unit at the Universitary Hospital of the Jundiaí Medical College, State of São Paulo, Brazil

INTRODUCTION

This study aimed to isolate and identify Candida spp. from the environment, health practitioners, and patients with the presumptive diagnosis of candidiasis in the Pediatric Unit at the Universitary Hospital of the Jundiaí Medical College, to verify the production of enzymes regarded as virulence factors, and to determine how susceptible the isolated samples from patients with candidiasis are to antifungal agents.

METHODS

Between March and November of 2008 a total of 283 samples were taken randomly from the environment and from the hands of health staff, and samples of all the suspected cases of Candida spp. hospital-acquired infection were collected and selected by the Infection Control Committee. The material was processed and the yeast genus Candida was isolated and identified by physiological, microscopic, and macroscopic attributes.

RESULTS

The incidence of Candida spp. in the environment and employees was 19.2%. The most frequent species were C. parapsilosis and C. tropicalis among the workers, C. guilliermondii and C. tropicalis in the air, C. lusitanae on the contact surfaces, and C. tropicalis and C. guilliermondii in the climate control equipment. The college hospital had 320 admissions, of which 13 (4%) presented Candida spp. infections; three of them died, two being victims of a C. tropicalis infection and the remaining one of C. albicans. All the Candida spp. in the isolates evidenced sensitivity to amphotericin B, nystatin, and fluconazole.

CONCLUSIONS

The increase in the rate of hospital-acquired infections caused by Candida spp. indicates the need to take larger measures regarding recurrent control of the environment.

Ten years of mechanical complications of central venous catheterization in trauma patients

The study purpose was to determine the incidence of mechanical complications (MC) associated with central venous catheterization (CVC) and to evaluate their impact on outcomes. This was a retrospective review of trauma morbidity and mortality records at a Level I trauma center (1999 to 2009). Demographics and outcomes were extracted for all trauma patients with CVC. Patients developing MC were compared with those who did not. Four thousand eight hundred eighteen lines were placed in 2935 patients. Of these, 1.5 per cent (n = 73) had MC. A total of 64.4 per cent (n = 47) were pneumothoraces followed by arterial cannulation at 8.2 per cent (n = 6) and thrombosis at 6.8 per cent (n = 5). The rate of MC by access site was: subclavian 1.8 per cent (n = 52), internal jugular 1.2 per cent (n = 10), and femoral 0.3 per cent (n = 3) (P value for trend = 0.001). Change in management was required in 31.5 per cent (n = 23). Number of lines (P < 0.001), Injury Severity Score (P < 0.001), body mass index less than 20 kg/m(2) (P = 0.036), and chest Abbreviated Injury Score greater than 3 (P = 0.034) were significant predictors of MC. Patients with MC had a longer intensive care unit length of stay (18.8 ± 25.7 vs 11.4 ± 13.3; adjusted odds ratio, 5.75; 95% confidence interval, 2.24-9.25; P = 0.001). Incidence of MC was 1.5 per cent. Complications were clinically significant in 31.5 per cent and resulted in longer intensive care unit stays.

Detection of viable but non-culturable staphylococci in biofilms from central venous catheters negative on standard microbiological assays

Viable bacteria were sought in 44 Maki-negative biofilms from central venous catheters (CVCs) using epifluorescence microscopy after live/dead staining. Thirty (77%) samples contained viable but non-culturable (VBNC) cells; the majority were positive on real-time PCR specific for Staphylococcus epidermidis (one also for Staphylococcus aureus). Viable cells were significantly (p<0.01) associated with CVCs from febrile patients, three of whom showed S. epidermidis-positive blood cultures, suggesting that CVC-associated biofilms can be reservoirs for staphylococci in the VBNC state. The possible role of VBNC staphylococci in persistent infections related to medical devices requires further investigation.

Synthesis of biomimetic segmented polyurethanes as antifouling biomaterials

Controlling the non-specific adsorption of proteins, cells and bacteria onto biomaterial surfaces is of crucial importance for the development of medical devices with specific levels of performance. Among the strategies pursued to control the interactions between material surfaces and biological tissues, the immobilization of non-fouling polymers on biomaterial surfaces as well as the synthesis of the so-called biomimetic polymers are considered promising approaches to elicit specific cellular responses. In this study, in order to obtain materials able to prevent infectious and thrombotic complications related to the use of blood-contacting medical devices, heparin-mimetic segmented polyurethanes were synthesized and fully characterized. Specifically, sulfate or sulfamate groups, known to be responsible for the biological activity of heparin, were introduced into the side chain of a carboxylated polyurethane. Due to the introduction of these groups, the obtained polymers possessed a higher hard/soft phase segregation (lower glass transition temperatures) and a greater hydrophilicity than the pristine polymer. In addition, the synthesized polymers were able to significantly delay the activated partial thromboplastin time, this increased hemocompatibility being related both to polymer hydrophilicity and to the presence of the -SO3H groups. This last feature was also responsible for the ability of these biomimetic polymers to prevent the adhesion of a strain of Staphylococcus epidermidis.

A close cut: a technical report of endovascular removal of a penetrating intravascular foreign body after a lawn mowing injury

We present a case of endovascular retrieval of a penetrating foreign body that was originally lodged in the mediastinum and then migrated to the hepatic vein. The steel nail entered the thorax and traversed the left lung causing a pneumothorax. The patient underwent a thoracotomy, but the foreign body had migrated from its original mediastinal position. A postsurgical CT showed that the object was below the right hemidiaphragm. Diagnostic venogram demonstrated that the object was in the main hepatic vein. Using a double-snare technique, the object was safely and successfully removed from the hepatic vein via the right common femoral vein.

Comparison of phenotypic methods for the identification of Candida dubliniensis

BACKGROUND/PURPOSE

Mixed infections caused by different Candida species are the rule rather than the exception. The discrimination between the two closely related species Candida albicans and Candida dubliniensis is not trivial. Therefore, there is a need for fast, reliable, and inexpensive methods with high specificity for the identification and differentiation of these two Candida species, which are frequently detected in the oral cavities of patients with a human immunodeficiency virus infection.

METHODS

We applied several phenotypic identification methods (growth on Rice-agar, Bird-seed agar, CHROMagar Candida, API ID 32C; growth at 42 degrees C and 45 degrees C) and compared them with genotyping by arbitrarily primed-polymerase chain reaction.

RESULTS

A sensitivity of 44% for the identification of C. dubliniensis was achieved for growth on Rice-agar, 97% for discrimination on Bird-seed agar, 95% with the assimilation profile index API ID 32C, and 97% when grown at 45 degrees C. We found two API codes not described for C. dubliniensis so far. Additionally, 88% of our C. dubliniensis isolates assimilated palatinose, in contrast to the 1% described in the API reference manual.

CONCLUSION

According to our results, cultivation of Candida isolates on Bird-seed agar after screening on CHROMagar Candida is a very sensitive, simple, and cost-effective method for discriminating C. dubliniensis from C. albicans in routine practice.

Novel synergistic antibiofilm combinations for salvage of infected catheters

Biofilms on catheters are responsible for catheter-related bloodstream infections (CRBSIs), which cause significant mortality and morbidity. Antimicrobial catheter-lock solutions may salvage precious catheters by eradicating biofilms. Staphylococcus epidermidis and Candida albicans are frequently isolated organisms in CRBSIs. We evaluated N-acetylcysteine (NAC), EDTA, ethanol and talactoferrin (TLF) individually and in combination with antibiotics against biofilms of S. epidermidis and C. albicans to identify effective catheter-lock solutions. Minimum biofilm-eradication concentrations causing 50% inhibition (MBEC(50)) for EDTA, NAC, ethanol and TLF were determined against biofilms of S. epidermidis and C. albicans formed on 96-well microtitre plates. Biomass, mean thickness and viability of S. epidermidis and C. albicans biofilms were evaluated after exposure to MBEC(50) concentrations of EDTA, NAC, ethanol and TLF. Antimicrobial combinations of EDTA, NAC, ethanol and TLF with nafcillin, vancomycin, fluconazole and amphotericin B were evaluated systematically for synergy using combination indices (CIs). EDTA, NAC, ethanol and TLF significantly reduced biofilm biomass and mean thickness (P<0.05, one-way ANOVA) of monomicrobial and polymicrobial biofilms as evaluated by confocal microscopy. CIs evaluated at equipotency ratios, and 50, 75 and 90 % effects, showed that EDTA, NAC, ethanol and TLF were synergistic (CI <1) with antibiotics (with few exceptions) against biofilms of S. epidermidis and C. albicans. EDTA, NAC, ethanol and TLF inhibit monomicrobial and polymicrobial biofilms of neonatal strains of S. epidermidis and C. albicans, and are synergistic with antibiotics. Catheter-lock solutions of EDTA, NAC and ethanol alone or in combination with antibiotics may be used to salvage infected catheters, which will directly impact on patient morbidity and health-care costs.

Organoselenium coating on cellulose inhibits the formation of biofilms by Pseudomonas aeruginosa and Staphylococcus aureus

Among the most difficult bacterial infections encountered in treating patients are wound infections, which may occur in burn victims, patients with traumatic wounds, necrotic lesions in people with diabetes, and patients with surgical wounds. Within a wound, infecting bacteria frequently develop biofilms. Many current wound dressings are impregnated with antimicrobial agents, such as silver or antibiotics. Diffusion of the agent(s) from the dressing may damage or destroy nearby healthy tissue as well as compromise the effectiveness of the dressing. In contrast, the antimicrobial agent selenium can be covalently attached to the surfaces of a dressing, prolonging its effectiveness. We examined the effectiveness of an organoselenium coating on cellulose discs in inhibiting Pseudomonas aeruginosa and Staphylococcus aureus biofilm formation. Colony biofilm assays revealed that cellulose discs coated with organoselenium completely inhibited P. aeruginosa and S. aureus biofilm formation. Scanning electron microscopy of the cellulose discs confirmed these results. Additionally, the coating on the cellulose discs was stable and effective after a week of incubation in phosphate-buffered saline. These results demonstrate that 0.2% selenium in a coating on cellulose discs effectively inhibits bacterial attachment and biofilm formation and that, unlike other antimicrobial agents, longer periods of exposure to an aqueous environment do not compromise the effectiveness of the coating.

Synergistic activity of dispersin B and cefamandole nafate in inhibition of staphylococcal biofilm growth on polyurethanes

Antibiotic therapies to eradicate medical device-associated infections often fail because of the ability of sessile bacteria, encased in their exopolysaccharide matrix, to be more drug resistant than planktonic organisms. In the last two decades, several strategies to prevent microbial adhesion and biofilm formation on the surfaces of medical devices, based mainly on the use of antiadhesive, antiseptic, and antibiotic coatings on polymer surfaces, have been developed. More recent alternative approaches are based on molecules able to interfere with quorum-sensing phenomena or to dissolve biofilms. Interestingly, a newly purified beta-N-acetylglucosaminidase, dispersin B, produced by the gram-negative periodontal pathogen Actinobacillus actinomycetemcomitans, is able to dissolve mature biofilms produced by Staphylococcus epidermidis as well as some other bacterial species. Therefore, in this study, we developed new polymeric matrices able to bind dispersin B either alone or in combination with an antibiotic molecule, cefamandole nafate (CEF). We showed that our functionalized polyurethanes could adsorb a significant amount of dispersin B, which was able to exert its hydrolytic activity against the exopolysaccharide matrix produced by staphylococcal strains. When microbial biofilms were exposed to both dispersin B and CEF, a synergistic action became evident, thus characterizing these polymer-dispersin B-antibiotic systems as promising, highly effective tools for preventing bacterial colonization of medical devices.