1.Characterization of a novel small molecule that potentiates β-lactam activity against gram-positive and gram-negative pathogens.
Nair DR1, Monteiro JM2, Memmi G1, Thanassi J3, Pucci M3, Schwartzman J1, Pinho MG2, Cheung AL4. Antimicrob Agents Chemother. 2015 Apr;59(4):1876-85. doi: 10.1128/AAC.04164-14. Epub 2015 Jan 12.
In a loss-of-viability screen using small molecules against methicillin-resistant Staphylococcus aureus (MRSA) strain USA300 with a sub-MIC of a β-lactam, we found a small molecule, designated DNAC-1, which potentiated the effect of oxacillin (i.e., the MIC of oxacillin decreased from 64 to 0.25 μg/ml). Fluorescence microscopy indicated a disruption in the membrane structures within 15 min of exposure to DNAC-1 at 2× MIC. This permeabilization was accompanied by a rapid loss of membrane potential, as monitored by use of the DiOC2 (3,3'-diethyloxacarbocyanine iodide) dye. Macromolecular analysis showed the inhibition of staphylococcal cell wall synthesis by DNAC-1. Transmission electron microscopy of treated MRSA USA300 cells revealed a slightly thicker cell wall, together with mesosome-like projections into the cytosol. The exposure of USA300 cells to DNAC-1 was associated with the mislocalization of FtsZ accompanied by the localization of penicillin-binding protein 2 (PBP2) and PBP4 away from the septum, as well as mild activation of the vraRS-mediated cell wall stress response.
2.Use of multiparameter flow cytometry to determine the effects of monoterpenoids and phenylpropanoids on membrane polarity and permeability in staphylococci and enterococci.
Hammer KA1, Heel KA. Int J Antimicrob Agents. 2012 Sep;40(3):239-45. doi: 10.1016/j.ijantimicag.2012.05.015. Epub 2012 Jul 12.
Monoterpenoids and phenylpropanoids are major components of many plant essential oils and are relatively simple, low-molecular-weight compounds with antimicrobial activity. This study used multiparameter flow cytometry to examine changes in membrane polarity and permeability in Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis following exposure to the monoterpenoids carvacrol, 1,8-cineole and terpinen-4-ol and the phenylpropanoids eugenol and cinnamaldehyde. Melaleuca alternifolia (tea tree) essential oil was also investigated. The fluorescent dyes DiOC(2)(3) (3,3'-diethyloxacarbocyanine oxide) and TO-PRO(®)-3 were used to assess membrane potential and permeability, respectively, following treatment with the minimum inhibitory concentration (MIC) of each test compound for 5 min and 30 min. Four subpopulations of cells were identified based on polarity and permeability. Eugenol treatment resulted in the greatest depolarisation and permeabilisation at 5 min, followed by carvacrol.
3.Reconfigurable Solid-state Dye-doped Polymer Ring Resonator Lasers.
Chandrahalim H1, Fan X1. Sci Rep. 2015 Dec 17;5:18310. doi: 10.1038/srep18310.
This paper presents wavelength configurable on-chip solid-state ring lasers fabricated by a single-mask standard lithography. The single- and coupled-ring resonator hosts were fabricated on a fused-silica wafer and filled with 3,3'-Diethyloxacarbocyanine iodide (CY3), Rhodamine 6G (R6G), and 3,3'-Diethylthiadicarbocyanine iodide (CY5)-doped polymer as the reconfigurable gain media. The recorded lasing threshold was ~220 nJ/mm(2) per pulse for the single-ring resonator laser with R6G, marking the lowest threshold shown by solid-state dye-doped polymer lasers fabricated with a standard lithography process on a chip. A single-mode lasing from a coupled-ring resonator system with the lasing threshold of ~360 nJ/mm(2) per pulse was also demonstrated through the Vernier effect. The renewability of the dye-doped polymer was examined by removing and redepositing the dye-doped polymer on the same resonator hosts for multiple cycles. We recorded consistent emissions from the devices for all trials, suggesting the feasibility of employing this technology for numerous photonic and biochemical sensing applications that entail for sustainable, reconfigurable, and low lasing threshold coherent light sources on a chip.
4.Dissimilar expression of multidrug resistance mdr1 and bcrp by the replication of hepatitis C virus: role of the nonstructural 5A protein.
W Rivero C1, Rosso N, Gentile E, Cuestas M, Tiribelli C, Oubiña JR, Mathet VL. J Viral Hepat. 2013 Apr;20(4):e127-30. doi: 10.1111/jvh.12028. Epub 2012 Nov 28.
Multidrug resistance associated with the overexpression of ATP-dependent binding cassette (ABC) proteins is widely accepted as an important cause of treatment failure in patients with neoplastic or infectious diseases. Some of them play also a pivotal role in detoxification processes. Herein, we investigated the effect of hepatitis C virus (HCV) replication and nonstructural 5A (NS5A) protein on the expression and functional activity of two ABC transport proteins: MDR1 and BCRP. RT-quantitative real-time polymerase chain reaction (qPCR) was carried out for mdr1 and bcrp mRNAs in both Huh7 cells expressing NS5A and Huh7.5 cells containing either full-length- or subgenomic-HCV replicon systems. The functional activity of these pumps was studied by performing a dye efflux assay with DiOC2 and Rhodamine 123. A dose-dependent down-regulation of mdr1 expression was documented in Huh7 cells expressing the NS5A protein, as well as in both replicon systems.