Methicillin-resistant Staphylococcus Aureus In Wounds Research Articles

Phospholipid membrane-protected photoelectrochemical chip: A specific test-to-treat platform for bacteria secreting pore-forming toxins with phosphatidylcholine receptor

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a frequent cause of purulent skin and soft tissue infections. In this study, a test-to-treat chip was developed as an integrated platform for the highly sensitive detection and treatment of MRSA infections. By integrating arginine (Arg) ligand-doped FeMOFs onto TiO2 nanotube arrays (TNT), the resulting Arg-FeMOF-TNT chips exhibited excellent photoelectrochemical (PEC) activity under visible-light irradiation. As phosphatidylcholine (PC) specific pore-forming toxins (PC-PFTs) secreted by MRSA can specifically generate small holes in the phospholipid membrane (PM), the PM covered Arg-FeMOF-TNT photoactive surface can be re-exposed to the electrolyte in the presence of PC-PFTs and then reacted with electron donors in the electrolyte. On the basis of switch-on PEC signals, a detection limit as low as 6 CFU mL−1 was achieved for MRSA. Furthermore, benefitting from its intrinsic photocatalytic activity, the Fenton-like catalytic activity of FeMOFs, and the loaded Arg on the chip, abundant reactive oxygen species (ROSs) and nitric oxide (NO, arginine decomposition product) were generated in the bacterial microenvironment, resulting in the effective sterilization of MRSA. Importantly, the PM modification endow the chip to process good biosafety and remarkable antibacterial specificity towards MRSA. Animal experiment results further demonstrated that the chip can rapidly kill MRSA in wounds and promote wound healing under 532-nm-laser irradiation. This all-in-one chip offers a new method for the diagnosing bacteria and also provides new insight into the design of test-to-treat platforms for PC-PFTs bacteria.

Biodegradable hydrogel with thermo-response and hemostatic effect for photothermal enhanced anti-infective therapy

Massive bleeding and infectious complication remain the leading cause of worldwide trauma deaths. To tackle this issue, a platelet-inspired degradable antibacterial hydrogel (Gel/PP-TA-Ag) is synthesized based on gelatin methacrylate (GelMA), tannic acid (TA), polyphosphate (PolyP) and gallic acid functionalized silver nanoparticles (Ag NPs) via a facile photopolymerization process. Accompanied by the degradation of the hydrogel, the released PolyP can activate the coagulation pathway, resulting in a better hemostatic effect than commercial gauze in the mice-bleeding model. Simultaneously, benefiting from hyperthermia originated from Ag NPs and photothermal accelerated release of TA and Ag+, 97.57% of methicillin-resistant Staphylococcus aureus (MRSA) and 95.99% of E. coli are eliminated in vitro. Moreover, in vivo experiments reveal that 91.76% of MRSA in wounds is removed, and the wound healing is effectively improved with more angiogenesis and collagen deposition. The level of inflammation in the wounds is also significantly reduced. As a result, Gel/PP-TA-Ag hydrogel possesses great potential in achieving satisfactory efficacy in infected wound healing.

An observational prospective study of topical acidified nitrite for killing methicillin-resistant Staphylococcus aureus (MRSA) in contaminated wounds

BackgroundEndogenous nitric oxide (NO) kills bacteria and other organisms as part of the innate immune response. When nitrite is exposed to low pH, NO is generated and has been used as an NO delivery system to treat skin infections. We demonstrated eradication of MRSA carriage from wounds using a topical formulation of citric acid (4.5%) and sodium nitrite (3%) creams co-applied for 5 days to 15 wounds in an observational prospective pilot study of 8 patients.FindingsFollowing treatment with topical citric acid and sodium nitrite, 9 of 15 wounds (60%) and 3 of 8 patients (37%) were cleared of infection. MRSA isolates from these patients were all sensitive to acidified nitrite in vitro compared to methicillin-sensitive S. aureus and a reference strain of MRSA.ConclusionsNitric oxide and acidified nitrite offer a novel therapy for control of MRSA in wounds. Wounds that were not cleared of infection may have been re-contaminated or the bioavailability of acidified nitrite impaired by local factors in the tissue.

Bacteriology of War Wounds at the Time of Injury

Bacterial contamination of war wounds occurs either at the time of injury or during the course of therapy. Characterization of the bacteria recovered at the time of initial trauma could influence the selection of empiric antimicrobial agents used to prevent infection. In the spring of 2004, U.S. military casualties who presented to the 31st Combat Support Hospital in Baghdad, Iraq, with acute traumatic injuries resulting in open wounds underwent aerobic culture of their wounds to identify the bacteria colonizing the wounds. Forty-nine casualties with 61 separate wounds were evaluated. Wounds were located predominantly in the upper and lower extremities and were primarily from improvised explosive devices or mortars. Thirty wounds (49%) had bacteria recovered on culture, with 40 bacteria identified. Eighteen casualties (20 wounds) had undergone field medical therapy (irrigation and/or antimicrobial treatment); six of these had nine bacterial isolates on culture. Of the 41 wounds from 31 patients who had received no previous therapy, 24 grew 31 bacteria. Gram-positive bacteria (93%), mostly skin-commensal bacteria, were the predominant organisms identified. Only three Gram-negative bacteria were detected, none of which were characterized as broadly resistant to antimicrobial agents. The only resistant bacteria recovered were two isolates of methicillin-resistant Staphylococcus aureus (MRSA). Our assessment of war wound bacterioly soon after injury reveals a predominance of Gram-positive organisms of low virulence and pathogenicity. The presence of MRSA in wounds likely reflects the increasing incidence of community-acquired MRSA bacteria. These data suggest that the use of broad-spectrum antibiotics with efficacy against more resistant, Gram-negative bacteria, such as Pseudomonas aeruginosa and Acinetobacter spp., is unnecessary in early wound management.

The evaluation of a cadexomer iodine wound dressing on methicillin resistant Staphylococcus aureus (MRSA) in acute wounds.

Many bacteria have become resistant to commonly-used antibiotics. The purpose of this study was to examine the effect of a cadexomer iodine wound dressing on methicillin resistant Staphylococcus aureus (MRSA). Partial thickness wounds were made on the backs of three pigs and inoculated with a known amount of MRSA. Wounds were treated with either cadexomer iodine dressing or vehicle dressing (without iodine), or they were left untreated. Three wounds from each treatment group per animal were cultured using quantitative scrub techniques after 24, 48, or 72 hours of treatment. The cadexomer iodine dressing significantly reduced MRSA and total bacteria in the wounds as compared to both the no treatment control and vehicle. No significant differences were observed in the number of bacteria recovered between the no treatment control and cadexomer (vehicle) treated wounds. Cadexomer iodine may be an effective agent for preventing proliferation of MRSA in wounds.