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BACKGROUND@#Research on the relationship between residential altitude and hypertension incidence has been inconclusive. Evidence at low altitudes (i.e., <1,500 m) is scarce, let alone in older adults, a population segment with the highest hypertension prevalence. Thus, the objective of this study is to determine whether hypertension risk may be affected by altitude in older adults living at low altitudes.@*METHODS@#This prospective cohort study collected data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS). We selected 6,548 older adults (≥65 years) without hypertension at baseline (2008) and assessed events by the follow-up surveys done in 2011, 2014, and 2018 waves. The mean altitude of 613 residential units (county or district) in which the participants resided was extracted from the Digital Elevation Model (DEM) of the National Aeronautics and Space Administration (NASA) and was accurate to within 30 m. The Cox regression model with penalized splines examined the linear or nonlinear link between altitude and hypertension. A random-effects Cox regression model was used to explore the linear association between altitude and hypertension.@*RESULTS@#The overall rate of incident hypertension was 8.6 per 100-person years. The median altitude was 130.0 m (interquartile range [IQR] = 315.5 m). We observed that the exposure-response association between altitude and hypertension incidence was not linear. The shape of the exposure-response curve showed that three change points existed. Hypertension risk increased from the lowest to the first change point (247.1 m) and slightly fluctuated until the last change point (633.9 m). The risk decreased above the last change point. According to the categories stratified by the change points, altitude was only significantly associated with hypertension risk (hazard ratio [HR] = 1.003; 95% confidence interval [CI] = 1.002-1.005) under the first change point (247.1 m) after adjusting for related covariates.@*CONCLUSION@#Our study found that the association between altitude and hypertension risk might not be linear. We hope the further study can be conducted to confirm the generality of our findings.
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Idoso , Humanos , Altitude , Hipertensão/etiologia , Incidência , Prevalência , Estudos ProspectivosRESUMO
Objective To evaluate the performance of Xpert C. difficile multiplex real-time PCR assay for diagnosis of Clostridium difficile infections in Chinese hospital settings. Methods This study was performed in Huashan Hospital, Ruijin Hospital, Beijing Hospital, Nanfang Hospital and Sir Run Run Shaw Hospital using a standard study protocol. Unique unformed stools from patients with acute hospital-acquired diarrhea were simultaneously analyzed by toxigenic anaerobic cultures and the Xpert C. difficile assay. All specimens displaying discordant results between the Xpert assay and toxigenic culture were sent for Sanger tcdB gene sequencing. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), total concordance rate, and 95％ confidence interval (CI) were calculated before and after resolution of discordant results using SAS 9.3. Results A total of 745 stool specimens were collected and 46 were excluded due to failure of C. difficile recovery. The remaining 699 specimens were included. Compared to the results of toxigenic culture, the sensitivity, specificity, PPV, and NPV of Xpert C. difficile assay were 94.1％ (144/153)(95％CI:89.1％-97.3％), 93.2％ (509/546)(95％CI:96.7％-99.2％), 79.6％ (144/181)(95％CI:72.9％-85.2％)and 98.3％ (509 / 518) (95％CI: 96.7％-99.2％), respectively. Both methods had a Kappa of 0.819. Xpert C. difficile assay showed sensitivity of 98.4％(62/63) (95％ CI: 90.3％-99.9％) and specificity of 93.2％(509/546) (95％ CI: 90.8％-95.2％) for toxin A-negative toxin B-positive strains. After the discordant results resolved by tcdB gene sequencing, PCR assay provided better performance with high sensitivity, specificity, positive predictive value, and negative predictive value [98.8％ (171 / 173), 98.1％ (516 / 526), 94.5％ (171/181) and 99.6％ (516/518), respectively]. Conclusions Compared to the results of toxigenic culture, the sensitivity, specificity and NPV of Xpert C. difficile assay were 94.1％ (144/153) and 93.2％(509/546), respectively. With the results available within 1 h, Xpert C. difficile assay provides prompt and precise laboratory diagnosis in Chinese clinical settings.
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Objective To investigate the role of spo0A gene in growth and sporulation of Clostridium difficile clinical isolates. Methods ClosTron gene knock-out system was used to knock out the spo0A gene of C. difficile strain C25. Bacterial growth curve was plotted by measuring D600 with spectrophotometer in different phases of bacterial growth. Malachite green staining technique was used to count the number of vegetative cells and spores under optical microscope. The sporulation rate was calculated. Results The spo0A mutant and its C25 parental strain showed similar patterns of growth. However, after knock-out of spo0A gene, an asporogenous phenotype was built, while the parental strain could produce spores as usual.Conclusions The spo0A gene plays a key role in sporulation but not growth of C. difficile strain.
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Objective To explore a method for establishing the hamster model of Clostridium difficile-associated diarrhea (CDAD)and the indicators for its evaluation.Methods Clindamycin was administered to hamsters subcutaneously (day 1),and 24 h later infected with C.difficile clinical isolates KH1 (ribotype 027,106-108 CFU/mL)or SH9 (ribotype 001 ,108-1010 CFU/mL)by gavage.Animals were observed for CDAD symptoms such as diarrhea,weight loss and death.At the end of ob-servation period (day 7 or death),the cecum was collected from each animal for histological evaluation of inflammation.Results Following a single dose of 100 mg/kg clindamycin subcutaneously,all the animals challenged with KH1 (108 CFU/mL)devel-oped diarrhea and then died within 5 days.All the hamsters challenged with SH9 (1010 CFU/mL)developed diarrhea as well but only 66.7% died at the end of observation period.Among other groups,only one or none developed diarrhea and then died. The symptoms of hamsters with diarrhea included loose stool,wet tail and weight loss.On histological examination,conges-tion,hemorrhage and neutrophil infiltration of the mucosa were observed in the hamsters died of CDAD.Conclusions We have successfully established a hamster CDAD model that allows for future investigations.