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To explore the genotyping characteristics of human fecal Escherichia coli (E. coli) and the relationships between antibiotic resistance genes (ARGs) and multidrug resistance (MDR) of E. coli in Miyun District, Beijing, an area with high incidence of infectious diarrheal cases but no related data. Over a period of 3 years, 94 E. coli strains were isolated from fecal samples collected from Miyun District Hospital, a surveillance hospital of the National Pathogen Identification Network. The antibiotic susceptibility of the isolates was determined by the broth microdilution method. ARGs, multilocus sequence typing (MLST), and polymorphism trees were analyzed using whole-genome sequencing data (WGS). This study revealed that 68.09% of the isolates had MDR, prevalent and distributed in different clades, with a relatively high rate and low pathogenicity. There was no difference in MDR between the diarrheal (49/70) and healthy groups (15/24). We developed a random forest (RF) prediction model of TEM.1 + baeR + mphA + mphB + QnrS1 + AAC.3-IId to identify MDR status, highlighting its potential for early resistance identification. The causes of MDR are likely mobile units transmitting the ARGs. In the future, we will continue to strengthen the monitoring of ARGs and MDR, and increase the number of strains to further verify the accuracy of the MDR markers. [ABSTRACT FROM AUTHOR]

Background: Despite the large number of drug-resistant tuberculosis (TB) cases in China, few studies have comprehensively analyzed the drug resistance-associated gene mutations and genotypes in relation to the clinical characteristics of M. tuberculosis (Mtb) isolates. Methodology/Principal Findings: We thus analyzed the phenotypic and genotypic drug resistance profiles of 115 Mtb clinical isolates recovered from a tuberculosis referral hospital in Beijing, China. We also performed genotyping by 28 loci MIRU-VNTR analysis. Socio-demographic and clinical data were retrieved from medical records and analyzed. In total, 78 types of mutations (including 42 previously reported and 36 newly identified ones) were identified in 115 Mtb clinical isolates. There was significant correlation between phenotypic and genotypic drug resistance rates for first-line anti-TB drugs (P<0.001). Genotyping revealed 101 MIRU-VNTR types, with 20 isolates (17.4%) being clustered and 95 isolates (82.6%) having unique genotypes. Higher proportion of re-treatment cases was observed among patients with clustered isolates than those with unique MIRU-VNTR genotypes (75.0% vs. 41.1%). Moreover, clinical epidemiological links were identified among patients infected by Mtb strains belonging to the same clusters, suggesting a potential of transmission among patients. Conclusions/Significance: Our study provided information on novel potential drug resistance-associated mutations in Mtb. In addition, the genotyping data from our study suggested that enforcement of the implementation of genotyping in diagnostic routines would provide important information for better monitor and control of TB transmission. [ABSTRACT FROM AUTHOR]

The chemical composition of Beijing aerosol was measured during summer and winter. Two distinct episodes were identified. Water-soluble potassium (K+) increased significantly during the firework episode in winter with an episode to non-episode ratio of 4.97, whereas the biomass burning (BB) episode in summer was characterized by high episode to non-episode ratios of levoglucosan (6.38) and K+ (6.90). The BB and firework episodes had only a minor influence on the water-soluble OC (organic carbon) to OC ratio. Based on separate investigations of episode and non-episode periods, it was found that: (i) sulfate correlated strongly with both relative humidity and nitrate during the typical winter period presumably indicating the importance of the aqueous-phase oxidation of sulfur dioxide by nitrogen dioxide, (ii) oxalate and WSOC during both winter and summer in Beijing were mainly due to secondary formation, and (iii) high humidity can significantly enhance the formation potential of WSOC in winter. [Copyright &y& Elsevier]

BSTRACT Background and objective: The rapid increase in the number of multi-drug-resistant tuberculosis (MDR-TB) cases worldwide emphasizes the importance of rational use of key important life-saving second-line anti-TB drugs such as fluoroquinolones. In order to provide information for better case management, so as to minimize the further spread of extensively drug-resistant TB, a retrospective study was performed to assess the risk factors associated with fluoroquinolone resistance among TB patients attending the 309 Hospital in Beijing, China. Methods: Drug susceptibility testing results and clinical data for hospitalized TB patients for the period 2000-2010 were analysed. Univariate and multivariate analyses were used to determine the risk factors associated with fluoroquinolone-resistant TB. Results: From July 2000 to July 2010, ofloxacin resistance was observed in 306 of 3546 (8.6%) hospitalized TB patients who were tested. The independent risk factors associated with fluoroquinolone-resistant TB were being single (adjusted OR 1.65), being a migrant living in Beijing (adjusted OR 2.15), being a migrant from another area (adjusted OR 5.07), being a patient who was retreated (adjusted OR 2.84), exposure to fluoroquinolones (adjusted OR 2.73), having COPD (adjusted OR 3.53), having COPD with known exposure to fluoroquinolones (adjusted OR 2.47), having MDR-TB (adjusted OR 1.67), and having poly-resistant TB (adjusted OR 2.34). Conclusions: These findings suggest that in high-risk populations continuous surveillance of fluoroquinolone resistance should be maintained. In addition, programs should be implemented for the management of patients with MDR-TB and more complicated TB, so as to minimize the further spread of fluoroquinolone resistance and extensively drug-resistant TB. [ABSTRACT FROM AUTHOR]

Brown carbon (i.e., light-absorbing organic carbon, or BrC) exerts important effects on the environment and on climate in particular. Based on spectrophotometric absorption measurements on extracts of bulk aerosol samples, this study investigated the characteristics of BrC during winter in Beijing, China. Organic compounds extractable by methanol contributed approximately 85% to the organic carbon (OC) mass. Light absorption by the methanol extracts exhibited a strong wavelength dependence, with an average absorption Ångström exponent of 7.10 (fitted between 310 and 450 nm). Normalizing the absorption coefficient ( b abs ) measured at 365 nm to the extractable OC mass yielded an average mass absorption efficiency (MAE) of 1.45 m 2 /g for the methanol extracts. This study suggests that light absorption by BrC could be comparable with black carbon in the spectral range of near-ultraviolet light. Our results also indicate that BrC absorption and thus BrC radiative forcing could be largely underestimated when using water-soluble organic carbon (WSOC) as a surrogate for BrC. Compared to previous work relying only on WSOC, this study provides a more comprehensive understanding of BrC aerosol based on methanol extraction. [ABSTRACT FROM AUTHOR]

Abstract: Carbonaceous aerosol collected in Beijing, China was characterized by a stepwise-extraction thermal–optical-transmittance (SE-TOT) method which allows for a quantitative separation of organic aerosol into distinct fractions. About 55% of the total organic carbon (OC) could be extracted by a mixture of hexane, methylene chloride and acetone. The extractable OC was further isolated into non-polar, low-polar and high-polar OC which constituted 10%, 23% and 22% of the total OC, respectively. The sum of low-polar and high-polar OC was found to coincide well with the secondary OC predicted by the elemental carbon tracer method, indicating that the low-polar and high-polar OC are strongly associated with secondary organic aerosol. Moreover, it was suggested that high relative humidity could enhance the production of high-polar OC through aqueous-phase reactions, because high-polar OC correlated strongly with oxalate and the ratio of high-polar OC to low-polar OC was significantly higher during the sampling events with high relative humidity (1.23 ± 0.35) comparing with results from the low relative humidity days (0.79 ± 0.23). In addition, the extractable OC was shown to be light-absorbing. The results of this study suggest that the SE-TOT method could provide new insights into the characterization of carbonaceous aerosol. [Copyright &y& Elsevier]

An intercomparison of organic carbon (OC) and elemental carbon (EC) measurements was conducted based on ambient aerosol samples collected during four seasons in Beijing, China. Dependence of OC and EC values on the temperature protocol and the charring correction method is presented and influences of aerosol composition are investigated. EC was found to decrease with the peak inert mode temperature (Tpeak) such that EC determined by the IMPROVE (the Interagency Monitoring of Protected Visual Environments)-A protocol (Tpeak was 580 °C) was 2.85 ± 1.31 and 3.83 ± 2.58 times that measured by an alternative protocol with a Tpeak of 850 °C when using the transmittance and reflectance correction, respectively. It was also found that reflectance correction tends to classify more carbon as EC compared with transmittance; results from the IMPROVE-A protocol showed that the ratio of EC defined by reflectance correction (ECR) to that based on transmittance (ECT) averaged 1.50 ± 0.42. Moreover, it was demonstrated that emissions from biomass burning would increase the discrepancy between EC values determined by different temperature protocols. On the other hand, the discrepancy between ECR and ECT was strongly associated with secondary organic aerosol (SOA) which was shown to be an important source of the organics that pyrolyze during the inert mode of thermal-optical analysis. [ABSTRACT FROM AUTHOR]

Abstract: Ambient organic carbon (OC) to elemental carbon (EC) ratios include important information about the extent of secondary organic aerosol (SOA) production. Influences of the measurement methods on the OC to EC ratios were evaluated in Beijing. When analyzed by the IMPROVE-A temperature protocol, the presence of positive artifact would increase the OC to EC ratio by 14–36% based on the transmittance correction, whereas the ratio of the un-denuded filter was 1.12–1.31 times that of denuded filter when using the reflectance correction. The OC to EC ratios calculated by results from the transmittance correction showed more significant variation comparing with those based on the reflectance correction; and no correlation between them was found. SOA concentrations were predicted by the EC-tracer method to investigate effects of the charring correction methods. Estimated SOA based on the reflectance correction was found to be much lower comparing with that calculated by results from the transmittance correction. SOA based on the reflectance correction might be unreliable because it exhibited no correlation with water-soluble organic carbon (WSOC). On the other hand, WSOC and SOA based on the transmittance correction correlated well (R 2 = 0.77–0.94), indicating the secondary nature of WSOC in Beijing. [Copyright &y& Elsevier]

Fine particulate matter (PM 2.5) pollution in Beijing was investigated based on field observation and air quality modeling. Measurement results showed that when using elemental carbon (EC) as the reference component, concurrent increases were observed in the relative abundances of sulfate, nitrate, organic carbon (OC) and water-soluble organic carbon (WSOC) when RH exceeded ∼65% during winter. The observed increases could not be explained by variations of primary biomass burning emissions, instead they likely pointed to heterogeneous chemistry and presumably indicated that formation of secondary inorganic and organic aerosols might be related during winter haze events in Beijing. Large gaps were found in winter when comparing the observational and modeling results. In summer, RH exhibited little influence on the observed sulfate/EC, OC/EC or WSOC/EC, and the observed and modeled results were in general comparable for the concentrations of sulfate, EC and OC. This study suggests that distinct yet poorly-understood atmospheric chemistry may be at play in China's winter haze events, and it could be a substantial challenge to properly incorporate the related mechanisms into air quality models. • Increases in sulfate/EC and WSOC/EC were observed under humid winter conditions. • Formation of secondary organic and inorganic aerosols may be related. • Large gaps existed between the observational and modeling results in winter. • RH exhibited little influence on sulfate/EC and WSOC/EC in summer. • The observed and modeled results were generally comparable in summer. [ABSTRACT FROM AUTHOR]