Green Synthesis of Silver-Peptide Nanoparticles Generated by the Photoionization Process for Anti-Biofilm Application.

An alarming increase in antibiotic-resistant bacterial strains is driving clinical demand for new antibacterial agents. One of the oldest antimicrobial agents is elementary silver (Ag), which has been used for thousands of years. Even today, elementary Ag is used for medical purposes such as treating burns, wounds, and microbial infections. In consideration of the effectiveness of elementary Ag, the present researchers generated effective antibacterial/antibiofilm agents by combining elementary Ag with biocompatible ultrashort peptide compounds. The innovative antibacterial agents comprised a hybrid peptide bound to Ag nanoparticles (IVFK/Ag NPs). These were generated by photoionizing a biocompatible ultrashort peptide, thus reducing Ag ions to form Ag NPs with a diameter of 6 nm. The IVFK/Ag NPs demonstrated promising antibacterial/antibiofilm activity against reference Gram-positive and Gram-negative bacteria compared with commercial Ag NPs. Through morphological changes in Escherichia coli and Staphylococcus aureus, we proposed that the mechanism of action for IVFK/Ag NPs derives from their ability to disrupt bacterial membranes. In terms of safety, the IVFK/Ag NPs demonstrated biocompatibility in the presence of human dermal fibroblast cells, and concentrations within the minimal inhibitory concentration had no significant effect on cell viability. These results demonstrated that hybrid peptide/Ag NPs hold promise as a biocompatible material with strong antibacterial/antibiofilm properties, allowing them to be applied across a wide range of applications in tissue engineering and regenerative medicine.

Early biofouling detection using fluorescence-based extracellular enzyme activity.

Membrane-based filtration technologies have seen rapid inclusion in a variety of industrial processes, especially production of drinking water by desalination. Biological fouling of membranes is a challenge that leads to increased costs from efficiency reductions, membrane damage and ultimately, membrane replacement over time. Such costs can be mitigated by monitoring and optimizing cleaning processes for better prognosis. Monitoring bacterial accumulation in situ can therefore advance understanding of cleaning efficiency. A fluorescence-based sensor for early biofouling detection capable of measuring extracellular enzyme activity was developed and tested in a lab-scale seawater reverse osmosis (SWRO) biofouling model for use in monitoring bacterial accumulation proximal to the surface of a membrane. We tracked bacterial biomass accumulation rapidly and non-invasively using exogenously applied fluorogen-substrates and corroborated with optical coherence tomography imaging of the membrane surface in real-time. The selected fluorogen and fluorogen-substrate were characterized and down selected by high throughput screening in vitro for compatibility in seawater and profiled over relevant Red Sea desalination parameters (pH and temperature). This approach demonstrates the practicality of prototyping an early-detection biofouling sensor in membrane based processes, such as seawater desalination, using extracellular enzyme activity as a measure of bacterial abundance.

Bacteriophage Lysin CF-301, a Potent Antistaphylococcal Biofilm Agent.

Biofilms pose a unique therapeutic challenge because of the antibiotic tolerance of constituent bacteria. Treatments for biofilm-based infections represent a major unmet medical need, requiring novel agents to eradicate mature biofilms. Our objective was to evaluate bacteriophage lysin CF-301 as a new agent to target Staphylococcus aureus biofilms. We used minimum biofilm-eradicating concentration (MBEC) assays on 95 S. aureus strains to obtain a 90% MBEC (MBEC90) value of ≤0.25 µg/ml for CF-301. Mature biofilms of coagulase-negative staphylococci, Streptococcus pyogenes, and Streptococcus agalactiae were also sensitive to disruption, with MBEC90 values ranging from 0.25 to 8 µg/ml. The potency of CF-301 was demonstrated against S. aureus biofilms formed on polystyrene, glass, surgical mesh, and catheters. In catheters, CF-301 removed all biofilm within 1 h and killed all released bacteria by 6 h. Mixed-species biofilms, formed by S. aureus and Staphylococcus epidermidis on several surfaces, were removed by CF-301, as were S. aureus biofilms either enriched for small-colony variants (SCVs) or grown in human synovial fluid. The antibacterial activity of CF-301 was further demonstrated against S. aureus persister cells in exponential-phase and stationary-phase populations. Finally, the antibiofilm activity of CF-301 was greatly improved in combinations with the cell wall hydrolase lysostaphin when tested against a range of S. aureus strains. In all, the data show that CF-301 is highly effective at disrupting biofilms and killing biofilm bacteria, and, as such, it may be an efficient new agent for treating staphylococcal infections with a biofilm component.

Genome Sequence of a Multidrug-Resistant Strain of Stenotrophomonas maltophilia with Carbapenem Resistance, Isolated from King Abdullah Medical City, Makkah, Saudi Arabia.

The emergence and spread of multidrug-resistant (MDR) bacteria have been regarded as major challenges among health care-associated infections worldwide. Here, we report the draft genome sequence of an MDR Stenotrophomonas maltophilia strain isolated in 2014 from King Abdulla Medical City, Makkah, Saudi Arabia.

Combination therapy with lysin CF-301 and antibiotic is superior to antibiotic alone for treating methicillin-resistant Staphylococcus aureus-induced murine bacteremia.

Lysins are bacteriophage-derived enzymes that degrade bacterial peptidoglycans. Lysin CF-301 is being developed to treat Staphylococcus aureus because of its potent, specific, and rapid bacteriolytic effects. It also demonstrates activity on drug-resistant strains, has a low resistance profile, eradicates biofilms, and acts synergistically with antibiotics. CF-301 was bacteriolytic against 250 S. aureus strains tested including 120 methicillin-resistant S. aureus (MRSA) isolates. In time-kill studies with 62 strains, CF-301 reduced S. aureus by 3-log10 within 30 minutes compared to 6-12 hours required by antibiotics. In bacteremia, CF-301 increased survival by reducing blood MRSA 100-fold within 1 hour. Combinations of CF-301 with vancomycin or daptomycin synergized in vitro and increased survival significantly in staphylococcal-induced bacteremia compared to treatment with antibiotics alone (P < .0001). Superiority of CF-301 combinations with antibiotics was confirmed in 26 independent bacteremia studies. Combinations including CF-301 and antibiotics represent an attractive alternative to antibiotic monotherapies currently used to treat S. aureus bacteremia.