Beta toxin catalyzes formation of nucleoprotein matrix in staphylococcal biofilms

Biofilms are surface-associated communities of microbes encompassed by an extracellular matrix. It is estimated that 80% of all bacterial infections involve biofilm formation, but the structure and regulation of biofilms are incompletely understood. Extracellular DNA (eDNA) is a major structural component in many biofilms of the pathogenic bacterium Staphylococcus aureus, but its role is enigmatic. Here, we demonstrate that beta toxin, a neutral sphingomyelinase and a virulence factor of S. aureus, forms covalent cross-links to itself in the presence of DNA (we refer to this as biofilm ligase activity, independent of sphingomyelinase activity) producing an insoluble nucleoprotein matrix in vitro. Furthermore, we show that beta toxin strongly stimulates biofilm formation in vivo as demonstrated by a role in causation of infectious endocarditis in a rabbit model. Together, these results suggest that beta toxin cross-linking in the presence of eDNA assists in forming the skeletal framework upon which staphylococcal biofilms are established.     

Coagulation changes and edema formation during long-distance bus travel.

Long-distance travel in a cramped position by aircraft or by bus and car has been suggested to be associated with an increased risk for thromboembolic events. Recently, we demonstrated moderate activation of coagulation after a long-haul flight. At present the single contributing factors (i.e. hypoxia and low humidity on board an aircraft and prolonged sitting in an aircraft, car or bus inducing venous stasis) have not yet been investigated. Therefore we measured markers of coagulation and fibrinolysis as well as functional parameters of coagulation using activated thrombelastography in 19 healthy volunteers before, during and after a real 10-h bus journey. In addition, changes in leg volume were measured. Thrombelastography revealed moderate activation of coagulation in all travelers, which was accompanied by a significant increase in prothrombin fragment F1 + 2. Thrombin-antithrombin III complexes and D-dimer remained unchanged, and tissue-type plasminogen activator and plasminogen-activator inhibitor 1 decreased after travel. After the travel we found a significant increase in leg volume that was exclusively distributed in the calf. We conclude that beside long-haul flights also long-distance bus travel induces a certain activation of the coagulation system. Thus, it is questionable whether hypoxia is the crucial risk factor for thromboembolic events after long-haul flights.     

Antibodies against lepirudin are polyspecific and recognize epitopes on bivalirudin

Bivalirudin is a synthetic antithrombin sharing a sequence of 11 amino acids with the recombinant hirudin lepirudin. We investigated whether antilepirudin antibodies recognize epitopes on bivalirudin. Antilepirudin antibody-positive sera of 43 patients, treated with lepirudin for heparin-induced thrombocytopenia, were analyzed. Lepirudin- and bivalirudin-coated microtiter plates were used for antibody testing in an enzyme-linked immunosorbent assay (ELISA) system. Of the 43 sera-containing antibodies binding to lepirudin, 22 (51.2%) contained antibodies that also recognized bivalirudin. Binding of these antibodies to bivalirudin was inhibited by more than 70% by preincubation with high doses of bivalirudin. However, if lepirudin-coated microtiter plates were used, high concentrations of bivalirudin inhibited only 2 of the 43 positive sera by more than 30%. Therefore antihirudin antibodies must be polyspecific. The clinical consequences of this cross-reactivity are unknown but bivalirudin, targeted by antibodies of patients treated with lepirudin previously, could potentially boost antibody titers in such patients or even trigger an immune response by itself. Clinically significant antibody formation in response to bivalirudin monotherapy has not been observed, however. Yet, as lepirudin and antilepirudin antibodies have recently been implicated in severe anaphylactic reactions, caution is warranted when using bivalirudin in patients previously treated with lepirudin.     

Efficacy and impact of monophasic versus biphasic countershocks for transthoracic cardioversion of persistent atrial fibrillation

This report compares the cumulative efficacy of cardioversion and skeletal muscle injury after either damped sine wave monophasic or truncated exponential biphasic transthoracic cardioversion of persistent atrial fibrillation. The trial sought to refute the null hypothesis of therapeutic equivalence between monophasic and biphasic waveforms. Results of the study reveal similar cumulative efficacy of waveforms and greater levels of skeletal muscle damage when patients are younger and male, and when monophasic waveforms are used.     

Prolonged-release oxycodone/naloxone in opioid-naïve patients – subgroup analysis of a prospective observational study

Objective: Prolonged-release oxycodone/naloxone (OXN PR) showed improved gastrointestinal tolerability and equivalent analgesic efficacy compared to oxycodone alone in patients with non-cancer pain or cancer pain. This is the first dataset to demonstrate its effectiveness and safety compared to other strong opioids in opioid-naïve patients.

Methods: This is a subgroup analysis of a 4- to 6-week multicenter, observational study. A total of 162 opioid-naïve patients with moderate-to-severe pain of varying etiologies received either OXN PR or other strong opioids (control group). Documented parameters include pain relief (numeric rating scale), bowel function (Bowel Function Index [BFI]), pain-related functional impairment (Brief Pain Inventory Short Form), quality of life (QoL; EuroQol EQ-5D-3L) and a global therapy assessment.

Results: OXN group patients experienced a substantial clinically important reduction in mean pain intensity of 51.4%, compared to a 28.6% reduction in control patients. Although the BFI remained in the reference range in both groups, there was a difference between BFI changes during treatment in favor of OXN PR. The superior effectiveness of OXN PR was paralleled by greater improvements of pain interference and QoL and fewer adverse drug reactions compared to other strong opioids.

Conclusion: The favorable outcomes under real-life conditions suggest that OXN PR provides a valuable option for treatment of moderate-to-severe pain without using weak opioids first.     

Angiotensin II stimulation of NAD(P)H oxidase activity: upstream mediators

Angiotensin II (Ang II)-stimulated hypertrophy of vascular smooth muscle cells is mediated by reactive oxygen species (ROS) derived from NAD(P)H oxidases. The upstream signaling mechanisms by which Ang II activates these oxidases are unclear but may include protein kinase C, tyrosine kinases, phosphatidylinositol-3-kinase, and Rac, a small molecular weight G protein. We found that Ang II-stimulated ROS production is biphasic. The first phase occurs rapidly (peak at 30 seconds) and is dependent on protein kinase C activation. The larger second phase of ROS generation (peak at 30 minutes) requires Rac activation, because inhibition of Rac by either Clostridium difficile toxin A or dominant-negative Rac significantly inhibits Ang II-induced ROS production. Phosphatidylinositol-3-kinase inhibitors (wortmannin or LY294002) and the epidermal growth factor (EGF) receptor kinase blocker AG1478 attenuate both Rac activation and ROS generation. The upstream activator of EGF receptor transactivation, c-Src, is also required for ROS generation, because PP1, an Src kinase inhibitor, abrogates the Ang II stimulation of both responses. These results suggest that c-Src, EGF receptor transactivation, phosphatidylinositol-3-kinase, and Rac play important roles in the sustained Ang II-mediated activation of vascular smooth muscle cell NAD(P)H oxidases and provide insight into the integrated signaling mechanisms whereby Ang II stimulation leads to activation of the growth-related NAD(P)H oxidases.