Search

ABSTRACTThe rapidly growing mycobacterium M. abscessussensu lato is the causative agent of emerging pulmonary and skin diseases and of infections following cosmetic surgery and postsurgical procedures. M. abscessussensu latocan be divided into at least three subspecies: M. abscessussubsp. abscessus, M. abscessussubsp. massiliense, and M. abscessussubsp. bolletii. Clinical isolates of rapidly growing mycobacteria were previously identified as M. abscessusby DNA-DNA hybridization. More than 30% of these 117 clinical isolates were differentiated as M. abscessussubsp. massilienseusing combinations of multilocus genotyping analyses. A much more cost-effective technique to distinguish M. abscessussubsp. massiliensefrom M. abscessussubsp. abscessus, a multiplex PCR assay, was developed using the whole-genome sequence of M. abscessussubsp. massilienseJCM15300 as a reference. Several primer sets were designed for single PCR to discriminate between the strains based on amplicons of different sizes. Two of these single-PCR target sites were chosen for development of the multiplex PCR assay. Multiplex PCR was successful in distinguishing clinical isolates of M. abscessussubsp. massiliensefrom samples previously identified as M. abscessus. This approach, which spans whole-genome sequencing and clinical diagnosis, will facilitate the acquisition of more-precise information about bacterial genomes, aid in the choice of more relevant therapies, and promote the advancement of novel discrimination and differential diagnostic assays.

Near-infrared spectra of 15 high-redshift radio galaxies (HzRGs) located at 2 < z < 2.6 were obtained by the OH Airglow Suppressor spectrograph mounted on the Subaru telescope. The UV-optical line ratio diagnostic diagrams indicate that half of the observed HzRGs have extended emission-line regions with low metal abundance, photoionized by a flat-continuum active galactic nucleus such as a quasar. We also found two probable correlations between radio and rest-optical parameters: (1) HzRGs with massive hosts tend to have a redder rest-optical continuum, and (2) HzRGs with smaller radio sizes also show a redder optical continuum. On the basis of the correlations, the nature of HzRGs at 2 < z < 2.6 is discussed.

We present the results of a search for Lyman break galaxies (LBGs) at $z \sim 5$in a 618 square-arcmin field including the Hubble Deep Field-North (HDF-N) taken by the Subaru Prime Focus Camera. Utilizing the published redshift data of the HDF-N and its flanking fields, the color selection criteria were chosen so that LBGs could be picked out most efficiently and least contaminated by foreground objects. The numbers of detected LBG candidates were 96 in $23.0 \leq I_c \; (\mathrm{mag}) \leq 24.5$and 310 in $23.0 \leq I_c \leq 25.5$. There is a hint of a deficiency of bright blue galaxies, although it is not as clear as has been suggested for LBGs at $z \sim 3$to 4. With 305 LBG candidates in a 575 square-arcmin field, the rest-frame UV luminosity function of LBGs at $4.4 \lesssim z \lesssim 5.3$was derived statistically by considering both the contamination by objects at the intermediate redshift and the incompleteness of the survey. The fraction of the contamination was estimated to be $\sim 50 \%$in the faintest magnitude range. The completeness of the survey was $\sim 80\%$at the bright part of the sample, and $\sim 20\%$in the faintest magnitude range ($25.0 < I_c \leq 25.5$). The luminosity function of LBG candidates at $z \sim 5$did not show a significant difference from those of LBGs at $z \sim 3$and 4, though there might be a slight decrease in the fainter part. The UV luminosity density within the observational limit was 0.56–0.69 times smaller than that obtained for LBGs at $z \sim 3$, depending on the adopted cosmology and the integration range of the luminosity function. This decrease in the UV luminosity at $z \sim 5$compared to that at $z \sim 3$is due to the smaller number density of faint galaxies at $z \sim 5$. The similarity of the luminosity functions at redshifts 5 to 3 implies that most of the LBGs at $z \sim 5$should have faded out at $z \sim 3$, and that the LBGs at $z \sim 5$are different galaxies from those seen at $z \sim 3$, if we take the face values for the ages of the LBGs at $z \sim 3$obtained by a SED fitting in which a continuous star formation in an individual galaxy was assumed. However, if the star formation in LBGs is sporadic, the similarity of the luminosity function at $z \sim 3$and 5 would be explained. Such sporadic star formation has been suggested by hydrodynamical simulations and semi-analytic models with collisional starbursts, and the trend of the cosmic star formation history predicted by these studies resembles that estimated from an integration of the UV luminosity density within the observational limit.