Staphylococcus aureus nasal carriage in a Moroccan dialysis center and isolates characterization

Staphylococcus aureus, which has its ecological niche in the anterior nares, has been shown to cause a variety of infectious diseases mainly for patients in hemodialysis units. We performed this study to evaluate the prevalence of nasal S. aureus carriage among hemodialysis outpatients, to determine the antimicrobial susceptibility of isolates, to characterize the virulence genes, and to identify associated risk factors. Nares swab specimens were obtained from 70 outpatients on hemodialysis between March and June 2010. Samples were plated immediately onto S. aureus specific media and pattern of antibacterial sensitivity was determined using disk diffusion method. Polymerase chain reaction was used to detect nuc, mecA, and genes encoding staphylococcal toxins. Medical record of patients was explored to determine S.aureus carriage risk factors. Nasal screening identified 42.9% S. aureus carriers with only one (3.3%) methicillin‐resistant S. aureus isolate. Among the methicillin‐susceptible S. aureus isolates, high rate of penicillin resistance (81.8%) has been detected. The identified risk factors were male gender and age ≤ 30 years. Research of virulence factors showed a high genetic diversity among the 30 S. aureus isolates. Twenty‐one (70%) of them had at least one virulence gene, of which 3.3% were Panton‐Valentine leukocidin (lukS/F‐PV) genes. S. aureus carriage must be screened for at regular intervals in hemodialysis patients. Setting up a bacterial surveillance system is one of the strategies to understand the epidemiology of methicillin‐resistant S. aureus, to guide local antibiotic policy and prevent spread of antibiotic‐resistant S. aureus.     

Carriage of Staphylococcus aureus in the nose of patients on regular dialysis treatment using hemodialysis catheters

In the hemodialysis population, the incidence of Staphylococcus aureus colonization has been documented to be as high as 80%; effective prophylaxis of vascular access infection and bacteremia is a worthwhile goal in the management of hemodialysis population. Surveillance of 50 hemodialysis patients for S. aureus‐positive nasal cultures was performed by monthly nasal swabs over a 12‐month period. All patients were performing dialysis using hemodialysis catheters thrice weekly. All positive cultures were treated with a prophylactic antibiotic regimen. Thirty‐one patients (62%) had one or more positive cultures. The surveillance period was longer in the S. aureus nasal carriers (p < 0.01). The frequency of positive cultures correlated with the duration of surveillance (p < 0.05). The incidence of S. aureus bacteremia was greater in patients with three or more positive cultures (p < 0.05). This study suggests that continuous surveillance for S. aureus nasal colonization is essential to properly identify all hemodialysis patients using catheters at risk of developing S. aureus bacteremias.     

Glucose variability in maintenance hemodialysis patients with type 2 diabetes: Comparison of dialysis and nondialysis days

Introduction

Hemodialysis (HD) induces several physiological changes that can affect plasma glucose levels in patients with diabetes and in turn their glycemic control. Studies using continuous glucose monitoring (CGM) to assess glucose variations on dialysis days compared with nondialysis days report conflicting results. Here, we used CGM to examine glucose variations induced by HD in patients with type 2 diabetes.

Methods

Patients with type 2 diabetes undergoing maintenance HD were included. CGM (Ipro2®, Medtronic) was performed at baseline and Week 4, 8, 12, and 16 for up to 7 days at each visit. CGM profiles on days where participants received HD were compared with days without HD using a linear mixed model.

Findings

Twenty-seven patients were included. The median number of CGM days performed was 8 (interquartile range [IQR] 6–10) for dialysis days and 16 (IQR 12–17) for nondialysis days. The median sensor glucose was 9.4 (95% confidence interval [CI] 8.8–10.2) mmol/L on dialysis days compared with 9.5 (95% CI 8.9–10.2) mmol/L on nondialysis days (p = 0.58). Nocturnal mean sensor glucose was higher on dialysis days compared with nondialysis days: 8.8 (95% CI 8.0–9.6) mmol/L versus 8.4 (95% CI 7.7–9.2) mmol/L (p = 0.029).

Discussion

Similar median sensor glucose values were found for days on and off HD. Nocturnal glucose levels were modestly increased on dialysis days. Our findings indicate that antidiabetic treatment does not need to be differentiated on dialysis versus nondialysis days in patients with type 2 diabetes undergoing maintenance HD.     

Relation between Access-Related Infection and Preinfection Serum Albumin Concentration in Patients on Chronic Hemodialysis

Background: Hemodialysis (HD) access‐related infection is a major cause of morbidity and mortality in HD patients. We tested whether hypoalbuminemia is a risk factor for HD access infection and whether mortality of HD catheter infection is affected by removal of the infected catheter. Methods: We analyzed the records of 87 patients on chronic HD who were hospitalized for HD access‐related infection. We obtained data on age, sex, preinfection serum albumin level, comorbidities, complications, infecting organism, type of infection, mode of management, and mortality. We compared preinfection serum albumin levels in 79 patients with HD access infection with the serum albumin levels of 198 control patients on chronic HD without HD access infection admitted to the hospital during the same time for other reasons. In the HD catheter infection subgroup, we compared mortalities between patients treated with catheter removal plus antibiotics as the primary mode of management and those treated initially with antibiotics alone. Results: Preadmission serum albumin level was lower in the HD access infection group (2.4 ± 0.6 g/dL) than in the control group (3.2 ± 0.6 g/dL, P < 0.0001). Logistic regression identified preadmission serum albumin level as a strong independent predictor of HD access infection. In a logistic regression model, with age, sex, HIV status, diabetes, and type of HD vascular access (excluding arterovenous fistula) as the covariates, the odds ratio of HD access infection was 9.8 (95% confidence interval [CI] 4.9–19.7) for a serum albumin level ≤ 3.0 g/dL (P < 0.0001), 10.4 (95% CI 4.97–21.6) for a serum albumin level ≤ 2.5 g/dL (P < 0.0001), and 28.0 (95% CI 5.8–135.9) for a serum albumin level ≤ 2.0 g/dL (P < 0.0001). Case mortality was 25.0% (4/16) in patients with tunneled HD catheter infection initially treated with antibiotics alone and 2.8% (2/71) in those treated with catheter removal plus antibiotics at the time of presentation (P = 0.0096). Conclusion: Hypoalbuminemia is associated with increased risk of HD access infection. Treatment of HD access infection with antibiotics alone is associated with increased risk of death.     

In vitro adhesion of staphylococci to diamond-like carbon polymer hybrids under dynamic flow conditions

This study compares the ability of selected materials to inhibit adhesion of two bacterial strains commonly implicated in implant-related infections. These two strains are Staphylococcus aureus (S-15981) and Staphylococcus epidermidis (ATCC 35984). In experiments we tested six different materials, three conventional implant metals: titanium, tantalum and chromium, and three diamond-like carbon (DLC) coatings: DLC, DLC–polydimethylsiloxane hybrid (DLC–PDMS-h) and DLC–polytetrafluoroethylene hybrid (DLC–PTFE-h) coatings. DLC coating represents extremely hard material whereas DLC hybrids represent novel nanocomposite coatings. The two DLC polymer hybrid films were chosen for testing due to their hardness, corrosion resistance and extremely good non-stick (hydrophobic and oleophobic) properties. Bacterial adhesion assay tests were performed under dynamic flow conditions by using parallel plate flow chambers (PPFC). The results show that adhesion of S. aureus to DLC–PTFE-h and to tantalum was significantly (P < 0.05) lower than to DLC–PDMS-h (0.671 ± 0.001 × 10⁷/cm² and 0.751 ± 0.002 × 10⁷/cm² vs. 1.055 ± 0.002 × 10⁷/cm², respectively). No significant differences were detected between other tested materials. Hence DLC–PTFE-h coating showed as low susceptibility to S. aureus adhesion as all the tested conventional implant metals. The adherence of S. epidermidis to biomaterials was not significantly (P < 0.05) different between the materials tested. This suggests that DLC–PTFE-h films could be used as a biomaterial coating without increasing the risk of implant-related infections.     

Methicillin‐resistant Staphylococcus aureus carriage in hospitalized chronic hemodialysis patients and its predisposing factors

There has been a paucity of literature on methicillin‐resistant Staphylococcus aureus (MRSA) colonization in chronic hemodialysis patients who required admission. The purpose of this study is to determine the MRSA carriage rate in hospitalized chronic hemodialysis patients, to identify the risk factors, and assess the consequences of MRSA colonization. This was a retrospective study of hospitalized chronic hemodialysis patients at Khoo Teck Puat Hospital from July 1, 2010 to June 30, 2011. MRSA screening was done on the day of admission using culture method with MRSA select (Bio‐Rad)?. The patients were divided into two groups: MRSA carriers and noncarriers. Demographic data, medical, and laboratory information was obtained via electronic medical record system. Outcome measures were infection rates during current hospitalization episode, frequency of hospitalization, and cumulative hospitalization days per year. Prevalence rate of MRSA colonization in hospitalized chronic hemodialysis patients was 15.1%, compared to all admitted patients (5.8%). Diabetes mellitus, Malay ethnicity, shorter hemodialysis duration and use of tunneled hemodialysis catheters were associated with MRSA colonization (P < 0.05). Relative risk of infection during the episode of admission among MRSA carriers was 3.2‐fold compared to noncarriers. MRSA colonization rates tend to be higher in patients on hemodialysis for less than 3 years and it correlates with longer hospitalization after adjustment for other variables (P < 0.05). Patients on chronic hemodialysis requiring admission have higher rates of MRSA colonization. The risk factors of MRSA carriers and the correlation of MRSA rates to longer hospitalization suggest its nosocomial origin in this group of patients.     

Nervous system autoantibodies and vitamin D receptor gene polymorphisms in hemodialysis patients

Cognitive deficits are prevalent in hemodialysis (HD) patients. Vitamin D deficiency and vitamin D receptor (VDR) gene single nucleotide polymorphism (SNPs) have been linked to both neurodegeneration (ND) and neuroprotection, respectively. Autoantibodies (Ab) to myelin basic protein (MBP), glial fibrillary acidic protein (GFAP), and neurofilament (NF) triplet proteins arise secondary to nervous system (NS) damage providing a means to assess neurological injury. Characterization of Ab biomarkers of NS damage in HD patients, their association with VDR SNPs, and nutritional vitamin D (NVD) therapy was performed. VDR genotypes, cytokines, and Ab biomarkers to NS proteins in HD subjects receiving ergocalciferol (n = 40) were compared with nonusers (n = 71). Interleukin‐6 (IL‐6), tumor necrosis factor‐α (TNF‐α), and immunoglobulin G (IgG) titers against NFs, GFAP, and MBP were measured by immunoassay. Subjects were genotyped for VDR SNPs BsmI (rs1544410) and FokI (rs2228570). Subjects (age 63.3 ± 16.1 years, 66% male) who were C allele carriers of BsmI had higher values of NF‐68 antibody titers (p = 0.027). Ergocalciferol users (n = 40) compared with nonusers (n = 71) had lower Ab titers to NS proteins; however, only anti–NF‐160 and anti‐MBP titers were significantly (p < 0.05) higher. IgG against NS proteins in HD patients suggests neuronal and glial insult and a relationship with VDR alleles. NVD may provide some neuroprotection, indicated by anti–NF‐160 and anti‐MBP, which was markedly lowered in ergocalciferol patients. This preliminary study suggests that Ab detection may be useful in monitoring ND and the potential of NVD for neuroprotection in HD patients.     

High‐dose cefazolin on consecutive hemodialysis in anuric patients with Staphylococcal bacteremia

Methicillin‐sensitive Staphylococcus aureus (MSSA) bacteremia is a leading cause of infection in hemodialysis (HD) patients. Cloxacillin, cefazolin, and vancomycin are the mainstay antimicrobials. Cloxacillin administration leads to frequent drug dosing, longer length of stay (LOS), and higher cost, while resistance and poorer outcomes are associated with vancomycin use. Dosing cefazolin during HD allows for prolonged blood therapeutic levels. We assessed the outcomes and safety of a strategy of treating MSSA bacteremia with 2–3 g cefazolin on HD only. All HD patients with MSSA bacteremia admitted in June–December 2009 at our center and receiving this regime were compared with historical controls who received cloxacillin. Demographic characteristics and outcome measures like mortality, LOS, cost, recrudescence, and adverse drug reactions were assessed. Of 27 consecutive episodes reviewed, 14 and 13 patients received cefazolin and cloxacillin, respectively. Baseline demographics were comparable between the 2 treatment groups. More than one‐third of the bacteremia was related to tunneled catheter infection. The 30‐day mortality of cloxacillin‐ and cefazolin‐treated patients was 15% and 7%, respectively (P=0.14). Two of the 11 survivors treated with cloxacillin (18%) had recrudescent bacteremia while none was observed in cefazolin‐treated survivors. Cefazolin was associated with shorter LOS (10 vs. 20 days, P<0.05) and lower cost (US$8262.00 vs. US$15,367.00, P<0.05). Cefazolin use resulted in 3 idiosyncratic adverse drug reactions. Cefazolin dosed on each HD in MSSA bacteremia leads to earlier discharge and less cost. Larger prospective studies are, however, warranted to fully assess its safety and efficacy.     

In Vitro Antimicrobial Effect of Encapsulated Vancomycin on Internalized Staphylococcus aureus Within Endothelial Cells

ABSTRACT

Vancomycin (VCN) is a glycopeptide antibiotic that is effective in the treatment of gram-positive bacterial infections, but mainly reserved for methicilin resistant Staphylococcus aureus. It is, however, ineffective against intracellular bacteria and hence a particulate form of VCN would be required. Bovine serum albumin (BSA) microspheres of VCN with a mean particle size of 5 ± 1.6 μm were used. Human microvascular endothelial cells internalized both S. aureus and VCN microspheres in a time and concentration-dependent manner, however, the uptake was inhibited by cytochalasin D. Action of VCN on S. aureus in the intracellular microenvironment decreased the bacterial load considerably.     

The effect of Nigella sativa seed extract concentration on crystal structure,band gap and antibacterial activity of ZnS-NPs prepared by green route

The present article investigates the effect of Nigella sativa seed extract concentration on crystal structure, band gap, and antibacterial activity of ZnS-NPs prepared by the green route. The study used a facile and eco-friendly method to obtain zinc sulfide nanoparticles (ZnS-NPs) using Nigella sativa seed (NSS) extract as a capping agent. XRD, SEM, FTIR, and UV–vis spectroscopy were employed to study the properties. The samples were also evaluated for antibacterial activity, and the obtained result shows pure crystalline ZnS-NPs with a cubic structure as being affirmed via powder XRD. FTIR spectra assert the existence of NSS extract as a capping agent. The SEM images of the obtained nanoparticles revealed that the prepared powders were composed of a mixture of fine and large grains of the product particles. The optical band gap computed from Tauc’s plot is found to decrease from 3.37 to 3.11 eV (Red shift). The antibacterial activity of ZnS-NPs was assessed on selected Gram-positive and Gram-negative bacteria strains (S. aureus and E. coli, respectively). The inhibition zones of ZnS-NPs were 26 and 19 mm for S. aureus and E. coli, respectively. The improved optical and antibacterial properties of ZnS-NPs make them suitable for optoelectronic applications and antibiotic development.

     

Infective spondylodiscitis in patients on high‐flux hemodialysis and on‐line hemodiafiltration

Infective spondylodiscitis (ISD) is a rare but potentially devastating condition in hemodialysis (HD) patients. Reports are limited especially in patients receiving high‐flux HD and hemodiafiltration (HDF). In a retrospective analysis, 13 patients on our maintenance high‐flux HD/HDF program were identified as having has infective spondylodiscitis over a 10‐year period (1997–2006), an incidence of approximately 1 episode every 215 patient‐years. The incidence was around 3 times higher in patients dialyzing with tunnelled central venous catheters (TCVC) than in those with arteriovenous fistulae. Affected patients were elderly (mean age 70 years) and had multiple comorbidities. Access problems, particularly TCVC infection, were common in the months preceding it's onset. Tunnelled central venous catheter removal during these episodes did not necessarily prevent it. Diagnosis was based on a history of back pain, raised C‐reactive protein, positive blood cultures, and characteristic magnetic resonance findings. Many patients were apyrexial and had normal white cell counts. In our patients on high‐flux HD/hemodiafiltration, its incidence appears comparable to that in conventional HD settings. No patients had infection with waterborne organisms. Blood cultures were positive in 77%. Gram‐positive organisms predominated, particularly Staphylococcus aureus. The major route of infection was hematogenous, with the most likely source the venous access. All received antibiotics for 6 to 12 weeks or until death. Only 2 patients underwent surgical drainage. Mortality was high (46%) and predicted by the development of complications, and by pre‐existing cardiovascular comorbidity. Prevention, using strategies to reduce the prevalence of bacteremia, including limiting the use of TCVC, should be an overriding aim.     

Probing the Role of Mucin‐Bound Glycans in Bacterial Repulsion by Mucin Coatings

Microbial colonization of implanted medical devices in humans can lead to device failure and life‐threatening infections. One strategy to prevent this unwanted colonization is to coat devices with polymers that reduce bacterial attachment. This study investigates how mucins, a class of biopolymers found in mucus, can be used as surface coatings to prevent attachment of selected respiratory pathogens to polystyrene surfaces. Our data show that coatings of porcine gastric mucins or bovine submaxillary mucins reduce surface attachment by Streptococcus pneumoniae and Staphylococcus aureus, but not Pseudomonas aeruginosa. To elucidate how mucin coatings repel S. pneumoniae and S. aureus, the molecular components of mucins are examined. Our data suggest that mucin‐bound glycans are key structural contributors of mucin coatings and are necessary for the repulsive effects toward S. pneumoniae and S. aureus.     

An investigation of microbial adhesion to natural and synthetic polysaccharide-based films and its relationship with the surface energy components

In recent years, polysaccharide-based films have been developed for many applications. Some of these are in the pharmaceutical industry, where the adhesion of microorganisms to surfaces is a concern. After adhesion of a microorganism to a solid surface has taken place, the subsequent biofilm formed can act as a vehicle for spreading infections. The aim of this study is to compare the bacterial adhesion of E. coli and S. aureus from a contaminated solid model (Tryptone Soya Agar) to a range of polysaccharide-based films. These polysaccharide-based films consist of different natural starches (potato, cassava, wheat, pea and rice) and synthetic polymers hydroxyl-propyl cellulose (HPC) and carboxyl methyl cellulose (CMC)). The surface energy parameters of the films were calculated from the contact angle measurements by the sessile drop method. Apolar and polar liquids (water, formamide and hexadecane) and the Lifshitz-Van der Waals/acid-base (LW/AB) approach were used according to the method of Van Oss, Chaundhury and Good. The surface properties of the films were also correlated to the microbial adhesion. This indicated that, for both E. coli and S. aureus, the surface roughness did not affect the microbial adhesion. Only had any correlation with the microbial adhesion and was almost constant for all the various polysaccharide films tested. In addition, the electron—donor properties of the materials, exhibited via , were positively correlated with the adhesion of S. aureus but not with E. coli. This was in agreement with the results of the MATS (Microbial Adhesion To Solvents) test performed on the two bacteria. This revealed that only S. aureus presented an electron—acceptor characteristic.     

The source of net ultrafiltration during hemodialysis is mostly the extracellular space regardless of hydration status

Fluid shifts are common in patients undergoing chronic hemodialysis (HD) during the intradialytic periods, as several liters of fluid are removed during ultrafiltration (UF). Some patients have experienced frequent intradialytic hypotension (IDH). However, the characteristics of fluid shifts and which fluid space is affected remain controversial. Therefore, we designed this study to evaluate the fluid spaces most affected by UF and to determine whether hydration status influences the fluid shifts during HD. This was a prospective cohort study of 40 patients undergoing HD. We measured the patient's fluid spaces using a whole‐body bioimpedance apparatus to evaluate the changes in the fluid spaces before HD and 1–4 hours of HD and 30 minutes after HD. UF achieved during HD by the 40 patients (age, 60.0 ± 5.2 years; 50% men; 50% of patients with diabetes; body weight, 61.3 ± 10.5 kg) was 2.18 ± 0.78 L (measured fluid overload, 2.15 ± 1.24 L). 1) Mean relative reduction of total body water and extracellular water was reduced from the start to the end of HD. 2) However, mean relative reduction of intracellular water was not reduced from the start to the end of HD. 3) No significant differences in fluid shifts were observed according to hydration status. The source of net UF during HD is mostly the extracellular space regardless of hydration status. Thus, IDH may be related to differences in the interstitial fluid shift to the vascular space.     

A Magneto-Heated Silk Fibroin Scaffold for Anti-Biofouling Solar Steam Generation

Macroscopic 3D porous materials are ideal solar evaporators for water purification. However, the limited sunlight intensity and penetrating depth during solar-driven evaporation cannot prevent the biofouling formation by photothermal effect, thus leading to the deterioration of evaporation rate. Herein, a magnetic heating strategy is reported for anti-biofouling solar steam generation based on a magnetic silk fibroin (SF) scaffold with bi-heating property. Under one sun, the solar-heated top surface of magnetic SF scaffolds accelerates water evaporation at 2.03 kg m⁻² h⁻¹, while the unheated inner channels suffer from the formation of biofilm. When exposed to alternating magnetic field (AMF), the magnetic SF scaffold can be integrally heated, leading to an efficient inner temperature to prevent biofouling in channels for water transportation. Accordingly, magneto-heated scaffolds show steady water evaporation rates after exposure to S. aureus and E. coli, which maintained 93.6–94.6% of original performance. In contrast, the evaporation rates of the scaffolds without AMF treatment are reduced to 1.31 (S. aureus) and 1.32 (E. coli) kg m⁻² h⁻¹, decreased by 35.5% and 35.0%, respectively. In addition, the magneto-heated scaffold inhibits biofouling formation in natural lake water, maintaining 99.5% original performance.     

Hepatocyte Growth Factor and Viral Load Variations in HD Session, Comparison with Molecular Absorbent Recirculating System (MARS) Therapy

A decrease in hepatitis C viral load in HD patients along HD sessions has been described. It has also been proposed that hepatocyte growth factor (HGF) stimulation by HD could have some protective effect in hepatitis C virus (HCV) liver disease outcome. Aims: (i) Measurement of HCV viral load variation and quantitation of HGF stimulation in CKD patients (HCV⁺ and HCV^–) on HD, along the HD session. (ii) Study whether albumin HD (MARS) decreases HCV viral load and stimulates HGF, compared to HD sessions. Methods: We performed two MARS and two HD sessions in vitro by using an extracorporeal circuit with blood bag contaminated with HCV serum with a known HCV viral load. (We used only a single blood bag for each testing.) In vivo we performed three MARS sessions. The total number of treatments was 6 in 2 patients (3 treatments each) and one HD session in 2 HCV⁺ patients and 5 HCV^– patients (included in HD program in our center), taking samples at the start of the following HD session, to compare the results with those obtained in vitro. We took samples at the beginning, middle, and at the end of MARS sessions in vivo and in vitro and starting (15 min) and at the end and before starting the following HD session in vivo. (The interval between 2 HD sessions in HCV⁺ patients was 2 days.) We determined HCV viral load using Amplicor (Roche) and HGF using ELISA (R&D System). Results: We found a decrease of viral load in vitro and in vivo both by MARS and HD. HD in vitro: ×decrease HCV viral load, 54.67%. HD in vitro × decrease viral load 30.6% × HD in vivo. We found a decrease of 30% in viral load, remaining 27.9% lower at the start of the following session. MARS in vitro: ×viral load decrease 3% (1 session in 2 experiments). MARS in vivo: ×viral load decrease of 44.5% (6 sessions in 2 patients). We did not find HCV viral load in ultrafiltrate or albumin from MARS procedure. Analyzing HGF stimulation we found the following:

Synergistic Chemotherapy and Photodynamic Therapy of Endophthalmitis Mediated by Zeolitic Imidazolate Framework‐Based Drug Delivery Systems

Endophthalmitis, derived from the infections of pathogens, is a common complication during the use of ophthalmology‐related biomaterials and after ophthalmic surgery. Herein, aiming at efficient photodynamic therapy (PDT) of bacterial infections and biofilm eradication of endophthalmitis, a pH‐responsive zeolitic imidazolate framework‐8‐polyacrylic acid (ZIF‐8‐PAA) material is constructed for bacterial infection–targeted delivery of ammonium methylbenzene blue (MB), a broad‐spectrum photosensitizer antibacterial agent. Polyacrylic acid (PAA) is incorporated into the system to achieve higher pH responsiveness and better drug loading capacity. MB‐loaded ZIF‐8‐PAA nanoparticles are modified with AgNO₃/dopamine for in situ reduction of AgNO₃ to silver nanoparticles (AgNPs), followed by a secondary modification with vancomycin/NH₂‐polyethylene glycol (Van/NH₂‐PEG), leading to the formation of a composite nanomaterial, ZIF‐8‐PAA‐MB@AgNPs@Van‐PEG. Dynamic light scattering, transmission electron microscopy, and UV–vis spectral analysis are used to explore the nanoparticles synthesis, drug loading and release, and related material properties. In terms of biological performance, in vitro antibacterial studies against three kinds of bacteria, i.e., Escherichia coli, Staphylococcus aureus, and methicillin‐resistant S. aureus, suggest an obvious superiority of PDT/AgNPs to any single strategy. Both in vitro retinal pigment epithelium cellular biocompatibility experiments and in vivo mice endophthalmitis models verify the biocompatibility and antibacterial function of the composite nanomaterials.     

Antibacterial activity of silver-modified natural clinoptilolite

The aim of the present work was to estimate the bactericidal activity and efficacy of silver pre-treated clinoptilolite-rich tuff from Marsid (Romania) in solid media (agar plates) against Gram-negative Escherichia coli ATCC 25922 and Gram-positive Staphylococcus aureus ATCC 25923. Two samples of natural clinoptilolite-rich tuff was first pre-treated with oxalic acid and sodium hydroxide solutions, respectively. The sample treated with oxalic acid was then exchanged with sodium chloride solution to obtain sodium form. Finally, both samples were exchanged with silver nitrate solution at room temperature for 24 h to obtain silver forms (P1-Ag⁺ and P2-Ag⁺) of clinoptilolite. The structure, morphology, and elemental composition of the pre-treated clinoptilolite samples were characterized by XRD, infrared (ATR-IR), SEM, and EDX analysis. The antibacterial activity was investigated by exposing E. coli and S. aureus in nutritive agar to the silver-clinoptilolite samples. Microorganisms were completely inhibited at 2 mg Ag⁺-clinoptilolite/mL nutritiv medium after 24 h of incubation at 37 °C. The silver-clinoptilolite sample derived from natural clinoptilolite pre-treated with oxalic acid (P1-Ag⁺) exhibit a stronger antibacterial effect in the presence of E. coli and the sample derived from natural clinoptilolite pre-treated with sodium hydroxide (P2-Ag⁺) in the presence of S. aureus.     

<Emphasis Type="Italic">Staphylococcus aureus</Emphasis> adhesion to standard micro-rough and electropolished implant materials

Implant-associated infections can cause serious complications including osteomyelitis and soft tissue damage, and are a great problem due to the emergence of antibiotic resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA). In some cases, antibiotic-loaded beads which release the antibiotic locally have been used, however such systems may lead to the development of antibiotic-resistant bacteria, as seen with gentamicin-loaded beads. Hence modifying the actual metal implant surface to inhibit or reduce initial bacterial adhesion may be an alternative option. This study describes the visualisation and quantification of S. aureus adhering to standard micro-rough ‘commercially pure’ titanium (TS) and Ti-6Al-7Nb (NS) surfaces, electropolished titanium (TE) and Ti-6Al-7Nb (NE) surfaces, and standard electropolished stainless steel (SS). Qualitative and quantitative results of S. aureus on the different surfaces correlated with each other, and showed significantly more live bacteria on NS than on the other surfaces, whilst there was no significant difference between the amount of bacteria on TS, TE, NE and SS surfaces. The results showed a significant decrease in the amount of bacteria adhering to the NE compared to standard NS surfaces. Such an observation suggests that the NS surface encouraged S. aureus adhesion, and could lead to higher infection rates in vivo. Hence electropolishing Ti-6Al-7Nb surfaces could be advantageous in osteosynthesis areas in minimising bacterial adhesion and lowering the rate of infection.     

Photosensitizer‐Modified MnO2 Nanoparticles to Enhance Photodynamic Treatment of Abscesses and Boost Immune Protection for Treated Mice

The emergence of drug‐resistant bacteria and easy recurrence has been challenging in the clinical treatment of skin abscesses resulting from bacterial infections (e.g., by Staphylococcus aureus (S. aureus)). Herein, an antibacterial nanoagent capable of modulating the abscess microenvironment is designed to enhance photodynamic treatment of skin abscesses, and subsequently activate the immune system to effectively prevent abscess recurrence. In the system, manganese dioxide nanoparticles (MnO₂ NPs) with high catalytic reactivity toward H₂O₂ are modified with photosensitizer chlorine e6 (Ce6) and coated with polyethylene glycol (PEG). The obtained Ce6@MnO₂‐PEG NPs, by triggering the decomposition of lesion endogenous H₂O₂, are able to effectively relieve the hypoxic abscess microenvironment during S. aureus infection. The light‐triggered photodynamic bacterial killing effect could thus be remarkably enhanced, resulting in effective in vivo therapy of S. aureus‐induced skin abscesses. Interestingly, a notable pathogen‐specific immunological memory effect against future infection by the same species of bacteria is elicited after such treatment, owing to the release of bacterial antigens post photodynamic therapy (PDT) together with the adjuvant‐like function of manganese ions to activate the host immune system. This work thus presents a new type of photodynamic nanoagent particularly promising for highly effective light‐triggered abscess treatment and prevention of abscess recurrence.