Use of silver in the prevention and treatment of infections: silver review

Impact of polymethylmethacrylate additives on methicillin-resistant Staphylococcus pseudintermedius biofilm formation in vitro

OBJECTIVE

To evaluate the impact of gentamicin, silver, or both additives in polymethylmethacrylate (PMMA) beads on methicillin-resistant Staphylococcus pseudintermedius (MRSP) biofilm formation in vitro.

SAMPLE

4 preparations of PMMA beads (formed with no additive [control], gentamicin, silver, and gentamicin and silver).

PROCEDURES

Beads from each group were exposed to 10 MRSP isolates known to be strong biofilm formers. Following incubation, the beads were rinsed to remove planktonic bacteria, then sonicated to dislodge biofilm-associated bacteria. Resulting suspensions were serially diluted, plated on blood agar, and incubated overnight; CFUs were counted. Variance of mean CFU counts following log10 transformation was analyzed among PMMA groups.

RESULTS

None of the PMMA additives tested completely inhibited MRSP biofilm formation. There was a significant effect of gentamicin and gentamicin plus silver on this variable, compared with controls, but not of silver alone. There was no difference between gentamicin and gentamicin plus silver. When only isolates not susceptible to gentamicin were evaluated, there were no significant differences among PMMA additive groups. Within gentamicin-susceptible isolates, there was an impact of gentamicin and gentamicin plus silver, but no impact of silver alone and no difference between gentamicin and gentamicin plus silver.

CONCLUSIONS AND CLINICAL RELEVANCE

Gentamicin-impregnated PMMA was effective at reducing biofilm formation of gentamicin-susceptible MRSP isolates but had no effect on isolates not susceptible to gentamicin. Silver-impregnated PMMA had no effect on MRSP biofilm formation. Results suggested that gentamicin-impregnated PMMA may not be effective in vivo against MRSP isolates not susceptible to gentamicin. Antibacterial efficacy of silver should not be assumed without proper testing of the target bacteria and specific silver compound.

Photoinduced formation of stable Ag-nanoparticles from a ternary ligand-DNA-Ag+ complex

The irradiation of a ternary complex between an intercalator crown-ether conjugate, double-stranded DNA, and Ag⁺ ions leads to the formation of stable Ag nanoparticles.

Ultrastructural changes in methicillin-resistant Staphylococcus aureus induced by positively charged silver nanoparticles

Silver nanoparticles offer a possible means of fighting antibacterial resistance. Most of their antibacterial properties are attributed to their silver ions. In the present work, we study the actions of positively charged silver nanoparticles against both methicillin-sensitive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus. We use aberration-corrected transmission electron microscopy to examine the bactericidal effects of silver nanoparticles and the ultrastructural changes in bacteria that are induced by silver nanoparticles. The study revealed that our 1 nm average size silver nanoparticles induced thinning and permeabilization of the cell wall, destabilization of the peptidoglycan layer, and subsequent leakage of intracellular content, causing bacterial cell lysis. We hypothesize that positively charged silver nanoparticles bind to the negatively charged polyanionic backbones of teichoic acids and the related cell wall glycopolymers of bacteria as a first target, consequently stressing the structure and permeability of the cell wall. This hypothesis provides a major mechanism to explain the antibacterial effects of silver nanoparticles on Staphylococcus aureus. Future research should focus on defining the related molecular mechanisms and their importance to the antimicrobial activity of silver nanoparticles.

Effectiveness of silver-impregnated central venous catheters for preventing catheter-related blood stream infections: a meta-analysis

OBJECTIVES

The purpose of this meta-analysis was to examine the effectiveness of silver-impregnated central venous catheters (CVCs) in preventing catheter bacterial colonization and catheter-related blood stream infections (CRBSIs).

METHODS

PubMed, Cochrane, and Embase databases were searched up to April 30, 2014. Studies in which other antiseptic reagents were used (e.g., chlorhexidine, octenidine dihydrochloride, urokinase rinses, benzalkonium chloride, rifampin-minocycline) were excluded. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Tests of heterogeneity and publication bias were performed.

RESULTS

Twelve studies were included in the meta-analysis. The studies enrolled a total of 2854 patients; 1440 received a standard CVC and 1414 received a silver-impregnated CVC. No significant difference in catheter bacterial colonization rates was found between silver-impregnated and standard CVCs (OR 0.907, 95% CI 0.758-1.087, p=0.290). No significant difference in CRBSI rates was found between silver-impregnated and standard CVCs (pooled OR 0.721, 95% CI 0.476-1.094, p=0.124). No significant heterogeneity or publication bias was noted.

CONCLUSIONS

Silver-impregnated CVCs are not associated with reduced rates of bacterial colonization or CRBSI.

Light-stable bis(norharmane)silver(I) compounds: synthesis, characterization and antiproliferative effects in cancer cells

Four different-anion Ag(I) compounds with the ligand norharmane (9H-Pyrido[3,4-b]indole; Hnor) and having the general formula [Ag(Hnor)2](anion) (anion=ClO4(-), NO3(-) and BF4(-)) [Ag(Hnor)2(MeCN)](PF6) are reported, and studied in detail regarding their coordination mode and in vitro antiproliferative effects. X-ray structural analysis revealed that the complex with the PF6(-) anion has a MeCN solvent molecule weakly coordinated to Ag(I), making the metal coordination T-shaped, while the other compounds present the classical linear Ag(I) coordination. The compounds showed certain cell growth inhibitory effects in two different cancer cell lines, with the perchlorate containing complex being the most toxic and in fact comparable to cisplatin. Notably, the compounds are stable in visible light; and the luminescence in the solid state was found to be extremely weak, whereas in MeOH solution all compounds show a moderate to weak emission band at 375 nm, when excited at 290 nm.

Novel amphiphilic cationic porphyrin and its Ag(II) complex as potential anticancer agents

In the present study we have synthesized a novel amphiphilic porphyrin and its Ag(II) complex through modification of water-soluble porphyrinic structure in order to increase its lipophilicity and in turn pharmacological potency. New cationic non-symmetrical meso-substituted porphyrins were characterized by UV-visible, electrospray ionization mass spectrometry (ESI-MS), (1)H NMR techniques, lipophilicity (thin-layer chromatographic retention factor, Rf), and elemental analysis. The key toxicological profile (i.e. cytotoxicity and cell line- (cancer type-) specificity; genotoxicity; cell cycle effects) of amphiphilic Ag porphyrin was studied in human normal and cancer cell lines of various tissue origins and compared with its water-soluble analog. Structural modification of the molecule from water-soluble to amphiphilic resulted in a certain increase in the cytotoxicity and a decrease in cell line-specificity. Importantly, Ag(II) porphyrin showed less toxicity to normal cells and greater toxicity to their cancerous counterparts as compared to cisplatin. The amphiphilic complex was also not genotoxic and demonstrated a slight cytostatic effect via the cell cycle delay due to the prolongation of S-phase. As expected, the performed structural modification affected also the photocytotoxic activity of metal-free amphiphilic porphyrin. The ligand tested on cancer cell line revealed a dramatic (more than 70-fold) amplification of its phototoxic activity as compared to its water-soluble tetracationic metal-free analog. The compound combines low dark cytotoxicity with 5 fold stronger phototoxicity relative to Chlorin e6 and could be considered as a potential photosensitizer for further development in photodynamic therapy.

Theodor Billroth's vision and Karl Ziegler's action: commemoration of the 40th day of death and the 50th anniversary of conferment of Nobel Prize for Chemistry of Karl Ziegler

Alloplastic materials are broadly used in modern surgery. Until the middle of the 20th century, metal materials and especially silver were used because of their antimicrobial properties. With the development of a new catalytic process for the production of high-density polyethylene and polypropylene materials, a new era of prosthesis was introduced. These polymers are integral part of our everyday operations surgery, especially in hernia repair. The famous surgeon Billroth mentioned to his pupil Czerny in 1878: "If we could artificially produce tissues of the density and toughness of fascia and tendon, the secret of the radical cure of hernia would be discovered". The polypropylene developed by Karl Ziegler gave the surgeon a material for daily practice, which in its properties (nearly) achieved Billroth's initial vision. In 1963 the Nobel Prize for Chemistry was awarded to Karl Ziegler and Giulio Natta in Stockholm. Furthermore, August 11, 2013 will be the 40th anniversary of Karl Ziegler's death. This manuscript honors both days.