Molecular Analysis of Levofloxacin-resistant Streptococcus pneumoniae in Japan

Quinolone resistance has been attributed to amino acid mutations in the type II topoisomerases of pathogens. To better understand this mechanism of resistance, we analyzed the molecular epidemiology of levofloxacin-resistant Streptococcus pneumoniae in Japan. We measured the quinolone susceptibility of 668 strains of S. pneumoniae obtained through nationwide surveillance from 2006 to 2008. We also sequenced the quinolone resistance-determining regions (QRDRs) in type II topoisomerases and analyzed the relationship between minimum inhibitory concentration (MIC) and six specific mutations (Ser81 or Glu85 in GyrA, Asp435 in GyrB, Ser79 or Asp83 in ParC, and Asp435 in ParE). Eighteen of the isolated strains (2.7%) showed intermediate susceptibility and resistance to levofloxacin (MIC > 4µg/ml), with no significant difference among years. However, garenoxacin and sitafloxacin showed excellent activity against these strains. Of the 18 strains, 17 (94.4%) showed mutation in QRDRs, while in 12 out of 14 levofloxacin-resistant strains (85.7%) two or more mutations were identified. A single QRDR mutation was found in 3 of 60 levofloxacin-susceptible strains (5%), all of which had an MIC of 2µg/ml. We therefore found a high isolation frequency of levofloxacin-resistant S. pneumonia in Japan over a 2-year period. Furthermore, QRDR mutations were present in 5% of susceptible strains; these were thought to be in the early stages of resistance. In the future, the increasing use of levofloxacin might result in more strain resistance. We therefore suggest that strong quinolones such as garenoxacin and sitafloxacin could be proactively administered to high-risk patients

Monitoring Quinolone Resistance Due to Mutations in GyrA and ParC in Haemophilus Influenzae（2012-17）

Knowing recent drug-resistant bacteria trends is important for proper antibacterial drug use to improve the prognosis of patients with infectious diseases and for public health. Because multiple quinolone antibacterial agents are simultaneously adopted in hospitals in Japan, we examined whether minimum inhibitory concentrations （MICs） against Haemophilus influenzae differ among quinolones. We determined MICs of six different quinolone antibacterial agents and performed molecular genetic analysis. We investigated β-lactamase-producing and β-lactamase-negative ampicillin-resistant（BLNAR）H. influenzae using the nitrocefin method in parallel. Overall, 144 clinical H. influenzae strains isolated at the Showa University Hospital between 2012 and 2017 were subjected to MIC determination for penicillin/quinolone antibacterial agents using the Clinical and Laboratory Standards Institute broth microdilution method. Amino acid mutations in the quinolone resistance-determining regions were analyzed in the isolates showing an MIC value ≥ 0.25µg/ml of quinolone antibacterial agents. BLNAR isolates increased from 2016 onward. Among quinolone antibacterial agents, all isolates remained susceptible to sitafloxacin. However, for moxifloxacin（MFLX）, strains with an MIC value＝0.5µg/ml were detected every year since 2013 except in 2015. Amino acid mutations were investigated in 17 isolates （11.8％） with MFLX MIC value≥ 0.25µg/ml and confirmed in 11 isolates （7.6％）, of which 9 contained GyrA mutations. The results demonstrated that MFLX was useful for predicting the presence of amino acid mutations and 0.25 was an appropriate MIC threshold for this purpose. This screening procedure may be effective for reducing the inappropriate use of quinolones and controlling the emergence of drug-resistant H. influenzae

Groeth Mode and Function of Aboral Spine Canopy in the Sand Dollar Scaphechinus mirabilis (A.Agassiz, 1863)

金沢大学大学院自然科学研究科神奈川大学Promoting Environmental Pesearch in Pan-Japan Sea Area : Young Researchers\u27 Network, Schedule: March 8-10,2006,Kanazawa Excel Hotel Tokyu, Japan, Organized by: Kanazawa University 21st-Century COE Program, Environmental Monitoring and Prediction of Long- & Short- Term Dynamics of Pan-Japan Sea Area ; IICRC(Ishikawa International Cooperation Research Centre), Sponsors : Japan Sea Research ; UNU-IAS(United Nations University Institute of Advanced Studies)+Ishikawa Prefecture Government ; City of Kanazaw

Phase diagram of ice polymorphs under negative pressure considering the limits of mechanical stability

Thermodynamic and mechanical stabilities of various ultralow-density ices are examined using computer simulations to construct the phase diagram of ice under negative pressure. Some ultralow-density ices, which were predicted to be thermodynamically metastable under negative pressures on the basis of the quasi-harmonic approximation, can exist only in a narrow pressure range at very low temperatures because they are mechanically fragile due to the large distortion in the hydrogen bonding network. By contrast, relatively dense ices such as ice Ih and ice XVI withstand large negative pressure. Consequently, various ices appear one after another in the phase diagram. The phase diagram of ice under negative pressure exhibits a different complexity from that of positive pressure because of the mechanical instability