No abstract

In recent years, increasing evidence has been collated on the contributions of fungal species, particularly Candida, to medical device infections. Fungal species can form biofilms by themselves or by participating in polymicrobial biofilms with bacteria. Thus, there is a clear need for effective preventative measures, such as thin coatings that can be applied onto medical devices to stop the attachment, proliferation, and formation of device-associated biofilms. However, fungi being eukaryotes, the challenge is greater than for bacterial infections because antifungal agents are often toxic towards eukaryotic host cells. Whilst there is extensive literature on antibacterial coatings, a far lesser body of literature exists on surfaces or coatings that prevent attachment and biofilm formation on medical devices by fungal pathogens. Here we review strategies for the design and fabrication of medical devices with antifungal surfaces. We also survey the microbiology literature on fundamental mechanisms by which fungi attach and spread on natural and synthetic surfaces. Research in this field requires close collaboration between biomaterials scientists, microbiologists and clinicians; we consider progress in the molecular understanding of fungal recognition of, and attachment to, suitable surfaces, and of ensuing metabolic changes, to be essential for designing rational approaches towards effective antifungal coatings, rather than empirical trial of coatings.

A common and revised nomenclature of the allotypes of the fourth component (C4) of human complement has been proposed. It is based on the results of the C4 Reference Typing of the Vlth Complement Genetics Workshop and Conference, Mainz, FRG, 1989, the previous C4 nomenclature and the guidelines for human gene nomenclature (ISGN). The designation of allotypes derives from their relative electrophoretic mobility, the distinction between C4A and C4B proteins from their relative hemolytic activity. Common alleles retain their single digit numeric designation, intermediate variants their two- or three-digit designations; newly discovered alleles should not interfere with already described variants. At least 13 C4A alleles, 16 C4B alleles as well as non-expressed genes at each C4 locus are presently known. There are also duplicated loci of each C4 gene; they should be designated by repetition of the locus symbol at the haplotype or genotype level. As a phenotype they will be placed in parenthesis without repetition of the locus symbol. Aberrant allotypes or hybrid genes should be explained by a special suffix. No special nomenclature is recommended for restriction fragment length polymorphisms. Their designation should follow the general rules of the ISGN.

We report a facile, one-step, aqueous surface bioconjugation approach for producing an antifungal surface coating that prevents the formation of fungal biofilms. By direct reaction between surface epoxide groups and amine groups on caspofungin, it avoids the use of secondary chemicals. The coating withstands washing with detergent and reduces the growth of the fungal pathogens Candida albicans by log 6 and Candida glabrata by log 3. Importantly, we show that surface adsorption of albumin does not inhibit the activity of this antifungal coating.Fungal infections in humans are a major medical problem, which globally kill as many people per year as tuberculosis.

There is a need for coatings for biomedical devices and implants that can prevent the attachment of fungal pathogens while allowing human cells and tissue to appose without cytotoxicity. Here, the authors study whether a poly(2-hydroxyethylmethacrylate) (PHEMA) coating can suppress attachment and biofilm formation by Candida albicans and whether caspofungin terminally attached to surface-tethered polymeric linkers can provide additional benefits. The multistep coating scheme first involved the plasma polymerization of ethanol, followed by the attachment of α-bromoisobutyryl bromide (BiBB) onto surface hydroxyl groups of the plasma polymer layer. Polymer chains were grafted using surface initiated activators regenerated by electron transfer atom transfer radical polymerization with 2-hydroxyethylmethacrylate, yielding PHEMA layers with a dry thickness of up to 89 nm in 2 h. Hydroxyl groups of PHEMA were oxidized to aldehydes using the Albright-Goldman reaction, and caspofungin was covalently immobilized onto them using reductive amination. While the PHEMA layer by itself reduced the growth of C. albicans biofilms by log 1.4, the addition of caspofungin resulted in a marked further reduction by >4 log units to below the threshold of the test. The authors have confirmed that the predominant mechanism of action is caused by antifungal drug molecules that are covalently attached to the surface, rather than out-diffusing from the coating. The authors confirm the selectivity of surface-attached caspofungin in eliminating fungal, not mammalian cells by showing no measurable toxicity toward the myeloid leukaemia suspension cell line KG-1a.

Antimicrobial surface coatings that act through a contact-killing mechanism (not diffusive release) could offer many advantages to the design of medical device coatings that prevent microbial colonization and infections. However, as the authors show here, to prevent arriving at an incorrect conclusion about their mechanism of action, it is essential to employ thorough washing protocols validated by surface analytical data. Antimicrobial surface coatings were fabricated by covalently attaching polyene antifungal drugs to surface coatings. Thorough washing (often considered to be sufficient to remove noncovalently attached molecules) was used after immobilization and produced samples that showed a strong antifungal effect, with a log 6 reduction in Candida albicans colony forming units. However, when an additional washing step using surfactants and warmed solutions was used, more firmly adsorbed compounds were eluted from the surface as evidenced by XPS and ToF-SIMS, resulting in reduction and complete elimination of in vitro antifungal activity. Thus, polyene molecules covalently attached to surfaces appear not to have a contact-killing effect, probably because they fail to reach their membrane target. Without additional stringent washing and surface analysis, the initial favorable antimicrobial testing results could have been misinterpreted as evidencing activity of covalently grafted polyenes, while in reality activity arose from desorbing physisorbed molecules. To avoid unintentional confirmation bias, they suggest that binding and washing protocols be analytically verified by qualitative/quantitative instrumental methods, rather than relying on false assumptions of the rigors of washing/soaking protocols.

For decades researchers have been targeting prevention of Rhodococcus equi (Rhodococcus hoagui/Prescottella equi) by vaccination and the horse breeding industry has supported the ongoing efforts by researchers to develop a safe and cost effective vaccine to prevent disease in foals. Traditional vaccines including live, killed and attenuated (physical and chemical) vaccines have proved to be ineffective and more modern molecular-based vaccines including the DNA plasmid, genetically attenuated and subunit vaccines have provided inadequate protection of foals. Newer, bacterial vector vaccines have recently shown promise for R. equi in the mouse model. This article describes the findings of key research in R. equi vaccine development and looks at alternative methods that may potentially be utilised.

Stable organic nitroxide radicals have been shown to exhibit similar cell biology signaling properties as the wellknown but short-lived small molecule nitric oxide, such as affecting intracellular redox states and cell proliferation behavior. Biological processes might thus be amenable to biointerfacial regulation via release of stable nitroxide molecules from coatings applied onto biomedical devices. In this study, we utilized the facile and technologically attractive process of plasma polymerization for the deposition of thin layers containing stable nitroxide radicals, using TEMPO (2,2,6,6tetramethylpiperidin-1-yl)oxyl as the "monomer" for creating a thin polymeric film. Coatings (TEMPOpps) produced under various conditions were characterized by ellipsometry, XPS, ToF-SIMS, and EPR as well as in vitro biological effects on bacteria (Staphylococcus epidermidis), fungi (Candida albicans), and human cancer cells (KG1a). TEMPOpps were compared with plasma coatings from three structurally related precursors that lack nitroxide groups. Surface characterization by XPS and ToF-SIMS confirmed the similarity of atomic composition and molecular fragments of the TEMPOpp films to the precursor molecule. Thin (241−312 nm) films were shown by EPR to contain stable nitroxide radicals, with a G-factor of 17 G typical of TEMPO. The plasma conditions modulated the density of radicals included in the films. On TEMPOpp surfaces, the microbial pathogens Staphylococcus epidermidis and Candida albicans exhibited reduced capacity to form biofilm, and fungal cells did not transition to hyphal forms. In addition, for the nonadherent human cancer cell line KG1a, we found that TEMPOpp coatings upregulated the cells' intracellular reactive oxygen species (ROS) but were not cytotoxic. Thus, we demonstrate that TEMPOpp films with nitroxide radicals possess versatile promising biological activities, such as for coating biomedical devices to prevent infections.