Semiquantitative Analysis of Clinical Heat Stress in Clostridium difficile Strain 630 Using a GeLC/MS Workflow with emPAI Quantitation.

<div><p><i>Clostridium difficile</i> is considered to be the most frequent cause of infectious bacterial diarrhoea in hospitals worldwide yet its adaptive ability remains relatively uncharacterised. Here, we used GeLC/MS and the exponentially modified protein abundance index (emPAI) calculation to determine proteomic changes in response to a clinically relevant heat stress. Reproducibility between both biological and technical replicates was good, and a 37°C proteome of 224 proteins was complemented by a 41°C proteome of 202 proteins at a 1% false discovery rate. Overall, 236 <i>C. difficile</i> proteins were identified and functionally categorised, of which 178 were available for comparative purposes. A total of 65 proteins (37%) were modulated by 1.5-fold or more at 41°C compared to 37°C and we noted changes in the majority of proteins associated with amino acid metabolism, including upregulation of the reductive branch of the leucine fermentation pathway. Motility was reduced at 41°C as evidenced by a 2.7 fold decrease in the flagellar filament protein, FliC, and a global increase in proteins associated with detoxification and adaptation to atypical conditions was observed, concomitant with decreases in proteins mediating transcriptional elongation and the initiation of protein synthesis. Trigger factor was down regulated by almost 5-fold. We propose that under heat stress, titration of the GroESL and dnaJK/grpE chaperones by misfolded proteins will, in the absence of trigger factor, prevent nascent chains from emerging efficiently from the ribosome causing translational stalling and also an increase in secretion. The current work has thus allowed development of a heat stress model for the key cellular processes of protein folding and export.</p></div

New technology: The sutureless valve prostheses

The sutureless concept of aortic valve implantation was developed in the early 1960s; however, this approach fell out of favour due to frequent valve-related thromboembolic complications and severe paravalvular leakage. More recently, with the advent of bovine pericardial valve prostheses, new sutureless and rapid deployment aortic valve prostheses have been reintroduced based on modern experience with transcatheter aortic valve implantation. There are two types of sutureless and rapid deployment aortic prostheses currently available on the market: the Perceval™ (LivaNova, Saluggia, Italy) and the Intuity Elite™ (Edwards Lifesciences, Irvine, Calif., USA) valves. By avoiding the placement and tying of sutures, sutureless aortic valve replacement (SU-AVR) has shown to minimize operative times and facilitate minimally invasive approaches. Moreover, current evidence suggests that sutureless and rapid deployment valves provide excellent haemodynamic results. Nevertheless, there is still a paucity of robust evidence on long-term SU-AVR outcomes; thus, to adequately assess the encouraging haemodynamic profile and the durability of these prostheses, further clinical trials are warranted