Isolation and characterisation of bacterial strains containing enantioselective DMSO reductase activity: application to the kinetic resolution of racemic sulfoxides

The kinetic resolution of racemic sulfoxides by dimethyl sulfoxide (DMSO) reductases was investigated with a range of microorganisms. Three bacterial isolates (provisionally identified as Citrobacter braakii, Klebsiella sp. and Serratia sp.) expressing DMSO reductase activity were isolated from environmental samples by anaerobic enrichment with DMSO as terminal electron acceptor. The organisms reduced a diverse range of racemic sulfoxides to yield either residual enantiomer depending upon the strain used. C. braakii DMSO-11 exhibited wide substrate specificity that included dialkyl, diaryl and alkylaryl sulfoxides, and was unique in its ability to reduce the thiosulfinate 1,4-dihydrobenzo-2, 3-dithian-2-oxide. DMSO reductase was purified from the periplasmic fraction of C. braakii DMSO-11 and was used to demonstrate unequivocally that the DMSO reductase was responsible for enantiospecific reductive resolution of racemic sulfoxides.

Reduction of Staphylococcus aureus and Pseudomonas aeruginosa colonisation on PVC through covalent surface attachment of fluorinated thiols

OBJECTIVES: This study reports the development, characterisation and microbiological testing of surface-modified polyvinylchloride (PVC) films for the purpose of reducing bacterial adherence.

METHODS: Irreversible covalent surface modification was achieved via nucleophilic substitution of fluorinated thiol-terminated compounds onto the polymer backbone. Four fluorinated modifiers, 2,3,5,6-tetrafluorothiophenol (TFTP), 4-(trifluoromethyl)thiophenol (TFMTP), 3,5-bis(trifluoromethyl)benzenethiol (BTFMBT) and 3,3,4,4,5,5,6,6,7, 7,8,8,9,9,10,10,10-heptadecafluoro-decane-1-thiol (HDFDT), were investigated. Modification was confirmed using attenuated total reflectance infrared spectroscopy; Raman mapping demonstrated that modification was homogenous on the macroscopic scale. The influence of fluorination on surface hydrophobicity was studied by contact angle analysis. The effect on microbial adherence was examined using Pseudomonas aeruginosa and Staphylococcus aureus.

KEY FINDINGS: The resultant changes in contact angle relative to control PVC ranged from -4 degrees to +14 degrees . In all cases, adherence of P. aeruginosa and S. aureus was significantly reduced relative to control PVC, with adherence levels ranging from 62% and 51% for TFTP-modified PVC to 32% and 7% for TFMTP-modified PVC.

CONCLUSIONS: These results demonstrate an important method in reducing the incidence of bacterial infection in PVC medical devices without compromising mechanical properties.

Pharmacology of transient receptor potential melastatin channels in the vasculature.

Mammalian transient receptor potential melastatin (TRPM) non-selective cation channels, the largest TRP subfamily, are widely expressed in excitable and non-excitable cells where they perform diverse functions ranging from detection of cold, taste, osmolarity, redox state and pH to control of Mg(2+) homeostasis and cell proliferation or death. Recently, TRPM gene expression has been identified in vascular smooth muscles with dominance of the TRPM8 channel. There has been in parallel considerable progress in decoding the functional roles of several TRPMs in the vasculature. This research on native cells is aided by the knowledge of the activation mechanisms and pharmacological properties of heterologously expressed TRPM subtypes. This paper summarizes the present state of knowledge of vascular TRPM channels and outlines several anticipated directions of future research in this area.

CD207+ CD103+ dermal dendritic cells cross-present keratinocyte-derived antigens irrespective of the presence of Langerhans cells.

Recent studies have challenged the view that Langerhans cells (LCs) constitute the exclusive antigen-presenting cells of the skin and suggest that the dermal dendritic cell (DDC) network is exceedingly complex. Using knockin mice to track and ablate DCs expressing langerin (CD207), we discovered that the dermis contains five distinct DC subsets and identified their migratory counterparts in draining lymph nodes. Based on this refined classification, we demonstrated that the quantitatively minor CD207+ CD103+ DDC subset is endowed with the unique capability of cross-presenting antigens expressed by keratinocytes irrespective of the presence of LCs. We further showed that Y-Ae, an antibody that is widely used to monitor the formation of complexes involving I-Ab molecules and a peptide derived from the I-E alpha chain, recognizes mature skin DCs that express I-Ab molecules in the absence of I-E alpha. Knowledge of this extra reactivity is important because it could be, and already has been, mistakenly interpreted to support the view that antigen transfer can occur between LCs and DDCs. Collectively, these data revisit the transfer of antigen that occurs between keratinocytes and the five distinguishable skin DC subsets and stress the high degree of functional specialization that exists among them.

Effect of sub-lethal challenge with Photodynamic Antimicrobial Chemotherapy (PACT) on the antibiotic susceptibility of clinical bacterial isolates

This study aimed to determine the effect of sub-lethal challenge with Photodynamic Antimicrobial Chemotherapy (PACT) on the susceptibility of clinical Staphylococcus aureus and Pseudomonas aeruginosa isolates to both PACT and a range of antibiotics used in the treatment of infection caused by these bacteria. Clinical S. aureus and P. aeruginosa isolates were exposed to sub-lethal PACT with meso-tetra (N-methyl-4-pyridyl) porphine tetra tosylate (TMP) and methylene blue (MB) over a 72 h period. After exposure, susceptibility of surviving organisms to a range of antibiotics was determined and compared with the susceptibility of an untreated control. Surviving bacteria were also exposed to previously lethal photosensitizer-light combinations, to determine if susceptibility to PACT was affected by sub-lethal exposure. Exposure to sub-lethal PACT did not decrease susceptibility to antibiotics with the minimum inhibitory concentrations for 95% and 100% of P. aeruginosa and S. aureus isolates, respectively, within two doubling dilutions of the MIC of the untreated control. Similarly, habituation with sub-lethal PACT did not reduce susceptibility of P. aeruginosa isolates to PACT levels previously determined as lethal. A reduction in susceptibility to PACT following habituation was apparent for two S. aureus isolates with MB and for 1 S. aureus isolate with IMP. However, for two of these three isolates, the log reduction for habituated cells was still greater than 4 log(10). PACT remains an attractive potential treatment for infection caused by these bacteria. (C) 2010 Elsevier B.V. All rights reserved.

Comparison of the cidal activity of tea tree oil and terpinen-4-ol against clinical bacterial skin isolates and human fibroblast cells

Aim: The aim of this study was to compare both the antimicrobial activity of terpinen-4-ol and tea tree oil (TTO) against clinical skin isolates of meticillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci (CoNS) and their toxicity against human fibroblast cells.