Accurate detection of oxacillin-resistant Staphylococcus lugdunensis by use of agar dilution.

BACKGROUND/PURPOSE: Staphylococcus lugdunensis is a Gram-positive coagulase-negative bacterium and is recognized as a critical pathogenic species recently. Here, we aimed to evaluate the cefoxitin disk diffusion (CDD), oxacillin agar dilution (OAD), and mecA PCR for detecting oxacillin-resistant S. lugdunensis (ORSL) isolates. METHODS: Multilocus sequence typing (MLST) analysis was performed to determine the clonality of 117 S. lugdunensis isolates isolated between May 2009 and Jul 2014. CDD, OAD, and mecA PCR were used to identify oxacillin-resistant S. lugdunensis (ORSL). RESULTS: MLST results showed that the most common sequence type (ST) of our S. lugdunensis isolates was ST6 (35.9%) followed by ST3 (28.2%), ST27 (17.9%), and ST4 (6.8%). CDD and OAD showed that 39 and 43 isolates were ORSL, respectively. 4 ST3 CDD-susceptible S. lugdunensis (OSSL) isolates had MIC values ≥ 4 for oxacillin. mecA PCR results showed that 43 OAD-resistant S. lugdunensis and 3 OAD-susceptible ST27 S. lugdunensis had the mecA gene. Therefore, OAD was used as the gold standard to evaluate the performance of CDD and mecA PCR for identifying ORSL. The overall sensitivity, specificity, and accuracy of CCD for ORSL detection was 90.7%, 100%, and 96.8%, respectively. The sensitivity, specificity, and accuracy of mecA PCR for identifying ORSL was 100%, 95.9%, and 97.44%, respectively. CONCLUSION: Our results indicate that OAD shows higher accuracy for ORSL detection compared with CDD and mecA PCR.

Synergistic Effect of Hydrochloric Acid and Phytic Acid Doping on Polyaniline-Coupled g-C3N4 Nanosheets for Photocatalytic Cr(VI) Reduction and Dye Degradation.

In this study, graphitic carbon nitride (g-C3N4) nanosheets (CNns) were modified using polyaniline (PANI) codoped with an inorganic (hydrochloric acid, HCl) and an organic (phytic acid, PA) acid. Our results revealed that these samples exhibited extended visible-light absorption and a three-dimensional (3D) hierarchical structure with a large specific surface area. They also inhibited photoluminescence emission, reduced electrical resistance, and provided abundant free radicals, resulting in high photocatalytic performance. The PANI/g-C3N4 sample demonstrated outstanding photocatalytic activity of a Cr(VI) removal capacity of 4.76 mg·min-1·gc-1, which is the best record for the reduction of a 100 ppm K2Cr2O7 solution. Moreover, g-C3N4 coupled with PANI monotonically doped with HCl or PA did not demonstrate increased activity, suggesting that the codoping of HCl and PA plays a significant role in enhancing the performance. The improved photocatalytic activity of PANI/g-C3N4 can be attributed to the interchain and intrachain doping of PA and HCl over PANI, respectively, to create a 3D connected network and synergistically increase the electrical conductivity. Therefore, new insights into g-C3N4 coupled with PANI and codoped by HCl and PA may have excellent potential for the design of g-C3N4-based compounds for efficient photocatalytic reactions.

Amino acids transitioning of 2009 H1N1pdm in Taiwan from 2009 to 2011.

A swine-origin influenza A was detected in April 2009 and soon became the 2009 H1N1 pandemic strain (H1N1pdm). The current study revealed the genetic diversity of H1N1pdm, based on 77 and 70 isolates which we collected, respectively, during the 2009/2010 and 2010/2011 influenza seasons in Taiwan. We focused on tracking the amino acid transitioning of hemagglutinin (HA) and neuraminidase (NA) genes in the early diversification of the virus and compared them with H1N1pdm strains reported worldwide. We identified newly emerged mutation markers based on A/California/04/2009, described how these markers shifted from the first H1N1pdm season to the one that immediately followed, and discussed how these observations may relate to antigenicity, receptor-binding, and drug susceptibility. It was found that the amino acid mutation rates of H1N1pdm were elevated, from 9.29×10(-3) substitutions per site in the first season to 1.46×10(-2) in the second season in HA, and from 5.23×10(-3) to 1.10×10(-2) in NA. Many mutation markers were newly detected in the second season, including 11 in HA and 8 in NA, and some were found having statistical correlation to disease severity. There were five noticeable HA mutations made to antigenic sites. No significant titer changes, however, were detected based on hemagglutination inhibition tests. Only one isolate with H275Y mutation known to reduce susceptibility to NA inhibitors was detected. As limited Taiwanese H1N1pdm viruses were isolated after our sampling period, we gathered 8,876 HA and 6,017 NA H1N1pdm sequences up to April 2012 from NCBI to follow up the dynamics of mentioned HA mutations. While some mutations described in this study seemed to either settle in or die out in the 2011-2012 season, a number of them still showed signs of transitioning, prompting the importance of continuous monitoring of this virus for more seasons to come.