Human blood plasma factors affect the adhesion kinetics of Staphylococcus aureus to central venous catheters

Staphylococcus aureus is a common cause of catheter-related blood stream infections (CRBSI). The bacterium has the ability to form multilayered biofilms on implanted material, which usually requires the removal of the implanted medical device. A first major step of this biofilm formation is the initial adhesion of the bacterium to the artificial surface. Here, we used single-cell force spectroscopy (SCFS) to study the initial adhesion of S. aureus to central venous catheters (CVCs). SCFS performed with S. aureus on the surfaces of naïve CVCs produced comparable maximum adhesion forces on three types of CVCs in the low nN range (~ 2-7 nN). These values were drastically reduced, when CVC surfaces were preincubated with human blood plasma or human serum albumin, and similar reductions were observed when S. aureus cells were probed with freshly explanted CVCs withdrawn from patients without CRBSI. These findings indicate that the initial adhesion capacity of S. aureus to CVC tubing is markedly reduced, once the CVC is inserted into the vein, and that the risk of contamination of the CVC tubing by S. aureus during the insertion process might be reduced by a preconditioning of the CVC surface with blood plasma or serum albumin

Hydroxyapatite Pellets as Versatile Model Surfaces for Systematic Adhesion Studies on Enamel : A Force Spectroscopy Case Study

Research into materials for medical application draws inspiration from naturally occurring or synthesized surfaces, just like many other research directions. For medical application of materials, particular attention has to be paid to biocompatibility, osseointegration, and bacterial adhesion behavior. To understand their properties and behavior, experimental studies with natural materials such as teeth are strongly required. The results, however, may be highly case-dependent because natural surfaces have the disadvantage of being subject to wide variations, for instance in their chemical composition, structure, morphology, roughness, and porosity. A synthetic surface which mimics enamel in its performance with respect to bacterial adhesion and biocompatibility would, therefore, facilitate systematic studies much better. In this study, we discuss the possibility of using hydroxyapatite (HAp) pellets to simulate the surfaces of teeth and show the possibility and limitations of using a model surface. We performed single-cell force spectroscopy with single Staphylococcus aureus cells to measure adhesion-related parameters such as adhesion force and rupture length of cell wall proteins binding to HAp and enamel. We also examine the influence of blood plasma and saliva on the adhesion properties of S. aureus. The results of these measurements are matched to water wettability, elemental composition of the samples, and the change in the macromolecules adsorbed over time on the surface. We found that the adhesion properties of S. aureus were similar on HAp and enamel samples under all conditions: Significant decreases in adhesion strength were found equally in the presence of saliva or blood plasma on both surfaces. We therefore conclude that HAp pellets are a good alternative for natural dental material. This is especially true when slight variations in the physicochemical properties of the natural materials may affect the experimental series

Randomization of Left-Right Asymmetry and Congenital Heart Defects The Role of DNAH5 in Humans and Mice

Background: Nearly one in 100 live births presents with congenital heart defects (CHD). CHD is frequently associated with laterality defects, such as situs inversus, a mirrored positioning of internal organs. Body laterality is established by a complex process: monocilia at the embryonic left-right organizer facilitate both the generation and sensing of a leftward fluid flow. This induces the conserved left-sided Nodal signaling cascade to initiate asymmetrical organogenesis. Primary ciliary dyskinesia originates from dysfunction of motile cilia, causing symptoms such as chronic sinusitis, bronchiectasis and frequently situs inversus totalis. The most frequently mutated gene in primary ciliary dyskinesia, DNAH5 is associated with randomization of body asymmetry resulting in situs inversus totalis in half of the patients; however, its relation to CHD occurrence in humans has not been investigated in detail so far. Methods: We performed genotype/phenotype correlations in 132 patients with primary ciliary dyskinesia carrying disease-causing DNAH5 mutations, focusing on situs defects and CHD. Using high-speed video microscopy-, immunofluorescence-, and in situ hybridization analyses, we investigated the initial steps of left-right axis establishment in embryos of a Dnah5-mutant mouse model. Results: In patients with primary ciliary dyskinesia carrying disease-causing DNAH5 mutations, 65.9% (87/132) had laterality defects: 88.5% (77/87) presented with situs inversus totalis, 11.5% (10/87) presented with situs ambiguus; and 6.1% (8/132) presented with CHD. In Dnah5(mut/mut) mice, embryonic left-right organizer monocilia lack outer dynein arms resulting in immotile cilia, impaired flow at the left-right organizer, and randomization of Nodal signaling with normal, reversed or bilateral expression of key molecules. Conclusions: For the first time, we directly demonstrate the disease-mechanism of laterality defects linked to DNAH5 deficiency at the molecular level during embryogenesis. We highlight that mutations in DNAH5 are not only associated with classical randomization of left-right body asymmetry but also with severe laterality defects including CHD