Reduction in the colonization of central venous cannulae by mupirocin

In an in-vitro simulation of an intravascular cannula enclosed in a fibrin sheath, 0.03 mg1(-1) of mupirocin prevented significant colonization [greater than 15 colony forming units (cfu)] by two clinical isolates of Staphylococcus epidermidis and one each of S. saprophyticus, S. hominis and S. haemolyticus. This suggests that in vivo, where protein binding of mupirocin is 95-97%, 1 mg 1(-1) of mupirocin at the cannula surface would be required to prevent colonization. These results support the findings of our previously published prospective controlled trial, in which mupirocin applied to the insertion sites of 172 internal jugular cannulae reduced the rate of colonization of cannula tips to 5%, compared with 25% for the 186 controls (P less than 0.001). Of the 46 colonized cannula tips from 110 control patients, the same species was isolated from the skin of the insertion site in 67% and from the lumen flush in only 15%. Analysed by patient, mupirocin reduced the proportion of patients with colonized tips from 17% to 3% after 24 h of infection, and from 35 to 10% after 48 h (P = 0.002). The use of agar containing charcoal, as a mupirocin neutralizer, and the incubation of tip-culture plates flooded with the Oxford staphylococcus, gave no evidence of carry over of mupirocin onto cannulae removed from mupirocin-treated patients

Minimal dose requirements for nasal mupirocin and its role in the control of epidemic MRSA

Staphylococci are still a leading cause of hospital infection. The success of nasal mupirocin for the control of epidemic methicillin- resistant Staphylococcus aureus (EMRSA), the prevention of colonization of central venous cannulae, and the prevention of septicaemia in haemodialysis patients should encourage the use of minimal dose regimens to minimize the emergence of mupirocin resistance. Mupirocin applied to the anterior nares 4-times daily usually eliminates S. aureus, including EMRSA, within 48 h. Elimination is sustained for several weeks in patients and staff. We recently found that a single dose, or a regimen of 4-times daily for 2 days, eliminated nasal carriage of S. aureus within 24 h; 7 days after a single dose, 92% of the subjects were still cleared; 7 days after the 2-day course, 96% remained free of nasal S. aureus. Ward personnel who are nasal carriers of EMRSA can, provided that other carriage sites are negative, return to work after 2 days of a 4-times daily intranasal regimen. The UK guidelines, recently published in this Journal, recommend an aggressive approach to identifying and eliminating EMRSA, including the elimination of nasal carriage. This approach is increasingly associated with the control of EMRSA in the UK and elsewhere

Evidence for an external origin of heavy elements in hot DA white dwarfs

We present a series of systematic abundance measurements for 89 hydrogen atmosphere (DA-type) white dwarfs with temperatures spanning 16000-77000K drawn from the FUSE spectral archive. This is the largest study to date of white dwarfs where radiative forces are significant, exceeding our earlier work, based mainly on IUE and HST data, by a factor three. Using heavy element blanketed non-LTE stellar atmosphere calculations, we have addressed the heavy element abundance patterns making completely objective measurements of abundance values and their error ranges using a \c{hi}2 fitting technique. We are able to establish the broad range of abundances seen in a given temperature range and establish the incidence of stars which appear, in the optical, to be atmospherically devoid of any material other than H. We compare the observed abundances to predictions of radiative levitation calculations, revealing little agreement. We propose that the supply of heavy elements is accreted from external sources rather than being intrinsic to the star. These elements are then retained in the white dwarf atmospheres by radiative levitation, a model that can explain both the diversity of measured abundances for stars of similar temperature and gravity, including cases with apparently pure H envelopes, and the presence of photospheric metals at temperatures where radiative levitation is no longer effective.Comment: 23 pages. 13 Figures, 4 Tables. Accepted for publication in the Monthly Notices of the Royal Astronomical Societ

Spectroscopically confirmed brown dwarf members of Coma Berenices and the Hyades

We have obtained low- and medium-resolution spectra of nine brown dwarf candidate members of Coma Berenices and the Hyades using SpEX on the NASA InfraRed Telescope Facility and Long Slit Intermediate Resolution Infrared Spectrograph on the William Herschel Telescope. We conclude that seven of these objects are indeed late M or early L dwarfs, and that two are likely members of Coma Berenices and four of the Hyades. Two objects, cbd40 and Hy3, are suggested to be field L dwarfs, although there is also a possibility that Hy3 is an unresolved binary belonging to the cluster. These objects have masses between 71 and 53MJup, close to the hydrogen-burning boundary for these clusters; however, only an optical detection of lithium can confirm if they are truly substellar

Irradiated brown dwarfs

We have observed the post common envelope binary WD0137-349 in the near infrared $J$, $H$ and $K$ bands and have determined that the photometry varies on the system period (116 min). The amplitude of the variability increases with increasing wavelength, indicating that the brown dwarf in the system is likely being irradiated by its 16500 K white dwarf companion. The effect of the (primarily) UV irradiation on the brown dwarf atmosphere is unknown, but it is possible that stratospheric hazes are formed. It is also possible that the brown dwarf (an L-T transition object) itself is variable due to patchy cloud cover. Both these scenarios are discussed, and suggestions for further study are made.Comment: 5 pages, 2 figures. Proceedings from "Brown dwarfs come of age" meeting in Fuerteventura 201

Origin of electron cyclotron maser-induced radio emissions at ultra-cool dwarfs: magnetosphere-ionosphere coupling currents

A number of ultra-cool dwarfs emit circularly polarised radio waves generated by the electron cyclotron maser instability. In the solar system such radio is emitted from regions of strong auroral magnetic field-aligned currents. We thus apply ideas developed for Jupiter's magnetosphere, being a well-studied rotationally-dominated analogue in our solar system, to the case of fast-rotating UCDs. We explain the properties of the radio emission from UCDs by showing that it would arise from the electric currents resulting from an angular velocity shear in the fast-rotating magnetic field and plasma, i.e. by an extremely powerful analogue of the process which causes Jupiter's auroras. Such a velocity gradient indicates that these bodies interact significantly with their space environment, resulting in intense auroral emissions. These results strongly suggest that auroras occur on bodies outside our solar system.Comment: Accepted for publication in the Astrophysical Journa

Hubble Space Telescope observations of the NUV transit of WASP-12b

We present new observations of four closely-spaced NUV transits of the hot Jupiter-like exoplanet WASP-12b using HST/COS, significantly increasing the phase resolution of the observed NUV light curve relative to previous observations, while minimising the temporal variation of the system. We observe significant excess NUV absorption during the transit, with mean normalised in-transit fluxes of $F_\mathrm{norm}\simeq0.97$, i.e. $\simeq$2-5 $\sigma$ deeper than the optical transit level of $\simeq0.986$ for a uniform stellar disk (the exact confidence level depending on the normalisation method used). We further observe an asymmetric transit shape, such that the post-conjunction fluxes are overall $\simeq$2-3 $\sigma$ higher than pre-conjunction values, and characterised by rapid variations in count rate between the pre-conjunction and out of transit levels. We do not find evidence for an early ingress to the NUV transit as suggested by earlier HST observations. However, we show that the NUV count rate observed prior to the optical transit is highly variable, but overall $\simeq$2.2-3.0 $\sigma$ below the post-transit values and comparable in depth to the optical transit, possibly forming a variable region of NUV absorption from at least phase $\phi\simeq$0.83, limited by the data coverage.Comment: Accepted into the Astrophysical Journa