The optochin susceptibility test is a key method for differentiating Streptococcus pneumoniae from other α-hemolytic streptococci;however, optochin-resistant (Optr) S. pneumoniae have been reported in the last two de...The optochin susceptibility test is a key method for differentiating Streptococcus pneumoniae from other α-hemolytic streptococci;however, optochin-resistant (Optr) S. pneumoniae have been reported in the last two decades. In this study, we investigated the isolation frequency of Optr S. pneumoniae in the North Kyushu area of Japan, and biochemically and genetically characterized Optr S. pneumoniae clinical isolates. Seven (0.68%) out of 1032 S. pneumoniae isolates collected by the North Fukuoka Infectious Diseases Working Group were found to be Optr S. pneumoniae. Resistant strains had MICs of optochin 2- to 64- fold higher than susceptible strains, possessed different antimicrobial resistance profiles, and belonged to different serotypes. All the seven Optr isolates had mutations in the nucleotide sequence code for subunit c of F0F1 ATPase. Three isolates had mutations in codon 48 (deduced amino acid substitution of valine with phenylalanine) and two isolates had mutations in codon 49 (substitution of alanine with threonine or serine). Of the remaining two isolates, one had mutation in codon 50 (substitution of phenylalanine with leucine) and the other had mutation in codon 44 (substitution of methionine with isoleucine, which was a novel mutation in this position). From these results, we identified the mutation in the H+-ATPase subunit c gene (atpC) of S. pneumoniae, which was not recognized earlier, and determined that Opt resistance among Japanese pneumococcal isolates is not related to a specific pneumococcal serotype or antimicrobial resistance profile. Furthermore, the results indicate that when α-hemolytic streptococci resistant to optochin are isolated from patients with invasive infectious diseases, such as meningitis and pneumonia, we should perform additional examinations such as bile solubility tests or PCR assays before confirming isolates as viridans streptococci. This is the first report of the characterization of Optr S. pneumoniae in Japan.展开更多
The multipath effect is a major Global Navigation Satellite System(GNSS)error source due to its environment-dependent characteristic,which complicates its mitigation process for the high-rate determination of displace...The multipath effect is a major Global Navigation Satellite System(GNSS)error source due to its environment-dependent characteristic,which complicates its mitigation process for the high-rate determination of displacements.For instance,Sidereal Filtering(SF)and Multipath Hemispherical Map(MHM)require the observations spanning at least one full cycle of satellite orbit repeat period(e.g.,ten days for Galileo navigation satellite system(Galileo)to reproduce the satellite geometry against ground stations.As a consequence,the practicability of SF and MHM is limited due to potential station-surrounding changes over a long period.In this study,we used the overlap-frequency signals on Global Positioning System(GPS)L1/L5,Galileo E1/E5a,and BeiDou-3 Navigation Satellite System(BDS-3)B1C/B2a to construct an interoperable MHM(i.e.,MHM_GEC)across constellations to mitigate multipath more efficiently.We thus used 31 days of 1-Hz GPS/Galileo/BDS-3 data at 21 stations in Europe to compare this overlap-frequency MHM with those GNSS-specific MHMs(i.e.,MHM_G for GPS,MHM_E for Galileo,and MHM_C for BDS-3),as well as SF.It is confirmed that the multipath effects on overlap-frequency signals are of a high spatial consistency across all GNSS.The mean reduction rate of applying MHM_GEC to GPS,Galileo,and BDS-3 carrier-phase residuals is 25%,31%,and 28.5%,respectively,which are up to 25 percentage points higher than those of MHM_G,MHM_E,and MHM_C.Furthermore,the MHM_GEC constructed using 5 to 6 days of data can improve the positioning precision by 40%,outperforming the MHM_E,MHM_C,and SF using 10 days of data.Therefore,the interoperable MHM_GEC is more efficient in mitigating multipath effects for high-precision GNSS positioning.展开更多
文摘The optochin susceptibility test is a key method for differentiating Streptococcus pneumoniae from other α-hemolytic streptococci;however, optochin-resistant (Optr) S. pneumoniae have been reported in the last two decades. In this study, we investigated the isolation frequency of Optr S. pneumoniae in the North Kyushu area of Japan, and biochemically and genetically characterized Optr S. pneumoniae clinical isolates. Seven (0.68%) out of 1032 S. pneumoniae isolates collected by the North Fukuoka Infectious Diseases Working Group were found to be Optr S. pneumoniae. Resistant strains had MICs of optochin 2- to 64- fold higher than susceptible strains, possessed different antimicrobial resistance profiles, and belonged to different serotypes. All the seven Optr isolates had mutations in the nucleotide sequence code for subunit c of F0F1 ATPase. Three isolates had mutations in codon 48 (deduced amino acid substitution of valine with phenylalanine) and two isolates had mutations in codon 49 (substitution of alanine with threonine or serine). Of the remaining two isolates, one had mutation in codon 50 (substitution of phenylalanine with leucine) and the other had mutation in codon 44 (substitution of methionine with isoleucine, which was a novel mutation in this position). From these results, we identified the mutation in the H+-ATPase subunit c gene (atpC) of S. pneumoniae, which was not recognized earlier, and determined that Opt resistance among Japanese pneumococcal isolates is not related to a specific pneumococcal serotype or antimicrobial resistance profile. Furthermore, the results indicate that when α-hemolytic streptococci resistant to optochin are isolated from patients with invasive infectious diseases, such as meningitis and pneumonia, we should perform additional examinations such as bile solubility tests or PCR assays before confirming isolates as viridans streptococci. This is the first report of the characterization of Optr S. pneumoniae in Japan.
基金funded by the National Natural Science Foundation of China (42025401)the Projects of International Cooperation and Exchanges NSFC (42361134580,42311530062).
文摘The multipath effect is a major Global Navigation Satellite System(GNSS)error source due to its environment-dependent characteristic,which complicates its mitigation process for the high-rate determination of displacements.For instance,Sidereal Filtering(SF)and Multipath Hemispherical Map(MHM)require the observations spanning at least one full cycle of satellite orbit repeat period(e.g.,ten days for Galileo navigation satellite system(Galileo)to reproduce the satellite geometry against ground stations.As a consequence,the practicability of SF and MHM is limited due to potential station-surrounding changes over a long period.In this study,we used the overlap-frequency signals on Global Positioning System(GPS)L1/L5,Galileo E1/E5a,and BeiDou-3 Navigation Satellite System(BDS-3)B1C/B2a to construct an interoperable MHM(i.e.,MHM_GEC)across constellations to mitigate multipath more efficiently.We thus used 31 days of 1-Hz GPS/Galileo/BDS-3 data at 21 stations in Europe to compare this overlap-frequency MHM with those GNSS-specific MHMs(i.e.,MHM_G for GPS,MHM_E for Galileo,and MHM_C for BDS-3),as well as SF.It is confirmed that the multipath effects on overlap-frequency signals are of a high spatial consistency across all GNSS.The mean reduction rate of applying MHM_GEC to GPS,Galileo,and BDS-3 carrier-phase residuals is 25%,31%,and 28.5%,respectively,which are up to 25 percentage points higher than those of MHM_G,MHM_E,and MHM_C.Furthermore,the MHM_GEC constructed using 5 to 6 days of data can improve the positioning precision by 40%,outperforming the MHM_E,MHM_C,and SF using 10 days of data.Therefore,the interoperable MHM_GEC is more efficient in mitigating multipath effects for high-precision GNSS positioning.
