An insight into the role of branched-chain α-keto acid dehydrogenase (BKD) complex in branched-chain fatty acid biosynthesis and virulence of Listeria monocytogenes.

Listeria monocytogenes is a foodborne bacterial pathogen that causes listeriosis. Positive regulatory factor A (PrfA) is a pleiotropic master activator of virulence genes of L. monocytogenes that becomes active upon the entry of the bacterium into the cytosol of infected cells. L. monocytogenes can survive and multiply at low temperatures; this is accomplished through the maintenance of appropriate membrane fluidity via branched-chain fatty acid (BCFA) synthesis. Branched-chain α-keto acid dehydrogenase (BKD), which is composed of four polypeptides encoded by lpd, bkdA1, bkdA2, and bkdB, is known to play a vital role in BCFA biosynthesis. Here, we constructed BKD-deficient Listeria strains by in-frame deletion of lpd, bkdA1, bkdA2, and bkdB genes. To determine the role in in vivo and in vitro, mouse model challenges, plaque assay in murine L2 fibroblast, and intracellular replication in J744A.1 macrophage were conducted. BKD-deficient strains exhibited defects in BCFA composition, virulence, and PrfA-regulon function within the host cells. Transcriptomics analysis revealed that the transcript level of the PrfA-regulon was lower in ΔbkdA1 strain than those in the wild-type. This study demonstrates that L. monocytogenes strains lacking BKD complex components were defective in PrfA-regulon function, and full activation of wild-type prfA may not occur within host cells in the absence of BKD. Further study will investigate the consequences of BKD deletion on PrfA function through altering BCFA catabolism.IMPORTANCEListeria monocytogenes is the causative agent of listeriosis, a disease with a high mortality rate. In this study, we have shown that the deletion of BKD can impact the function of PrfA and the PrfA-regulon. The production of virulence proteins within host cells is necessary for L. monocytogenes to promote its intracellular survival and is likely dependent on membrane integrity. We thus report a link between L. monocytogenes membrane integrity and the function of PrfA. This knowledge will increase our understanding of L. monocytogenes pathogenesis, which may provide insight into the development of antimicrobial agents.

Transitional care interventions reduce unplanned hospital readmissions in high-risk older adults.

BACKGROUND: Acute hospital services account for the largest proportion of health care system budgets, and older adults are the most frequent users. As a result, older people who have been recently discharged from hospital may be at greater risk of readmission. This study aims to evaluate the comparative effectiveness of transitional care interventions on unplanned hospital readmissions within 28 days, 12 weeks and 24 weeks following hospital discharge. METHOD: The present study was a randomised controlled trial (ACTRN12608000202369). The trial involved 222 participants who were recruited from medical wards in two metropolitan hospitals in Australia. Participants were eligible for inclusion if they were aged 65 years and over, admitted with a medical diagnosis and had at least one risk factor for readmission. Participants were randomised to one of four groups: standard care, exercise program only, Nurse Home visit and Telephone follow-up (N-HaT), or Exercise program and Nurse Home visit and Telephone follow-up (ExN-HaT). Socio-demographics, health and functional ability were assessed at baseline, 28 days, 12 weeks and 24 weeks. The primary outcome measure was unplanned hospital readmission which was defined as any hospital admission for an unforeseen or unplanned cause. RESULTS: Participants in the ExN-HaT or the N-HaT groups were 3.6 times and 2.6 times respectively significantly less likely to have an unplanned readmission 28 days following discharge (ExN-HaT group HR 0.28, 95% CI 0.09-0.87, p = 0.029; N-HaT group HR 0.38, 95% CI 0.13-1.07, p = 0.067). Participants in the ExN-HaT or the N-HaT groups were 2.13 and 2.63 times respectively less likely to have an unplanned readmission in the 12 weeks after discharge (ExN-HaT group HR 0.47, 95% CI 0.23-0.97, p = 0.014; N-HaT group HR 0.38, 95% CI 0.18-0.82, p = 0.040). At 24 weeks after discharge, there were no significant differences between groups. CONCLUSION: Multifaceted transitional care interventions across hospital and community settings are beneficial, with lower hospital readmission rates observed in those receiving more transitional intervention components, although only in first 12 weeks. TRIAL REGISTRATION: Australian and New Zealand Clinical Trial Registry ( ACTRN12608000202369 ).

Structural, electronic, and theoretical description of a series of cobalt clathrochelate complexes in the Co(III), Co(II) and Co(I) oxidation states.

Encaged hexacoordinated metal complexes have long been a fascinating family of complexes, as they confer the same ligand environment to metal ions in different oxidation states. We recently reported that cobalt clathrochelate complexes behave as hydrogen-producing catalysts at quite modest overpotential ( Pantani et al. Angew. Chem., Int. Ed. 2008 , 47 , 9948 ). The electrochemical properties evidenced two quasireversible one-electron reduction waves starting from the cobalt(III) derivative, indicating that there are no dramatic changes in the coordination sphere. The intriguing question is the mechanistic pathways for this observed reactivity. In this work, we compare our observed electrochemical and spectroscopic data (UV-visible and EPR spectroscopies) with our theoretical findings based on DFT, TD-DFT, and CASSCF calculations. The properties of the Co(III) and Co(II) species can be explained as low-spin complexes. In contrast, the doubly reduced species, the "Co(I)" form, is a high-spin complex and its electronic description involves partial reduction of the ligand cage. This point is of major importance to understand the catalytic activity.