Nitrogen variations during the ice-on season in the eutrophic lakes.

Nitrogen accumulation in sediments, and the subsequent migration and transformations between sediment and the overlying water, plays an important role in the lake nitrogen cycle. However, knowledge of these processes are largely confined to ice-free seasons. Recent research under ice has mainly focused on the water eco-environmental effects during winter. Sediment N accumulation during the ice-on season and its associated eco-environmental impacts have never been systematically investigated. To address these knowledge gaps, we chose Wuliangsu Lake in China as a case study site, taking advantage of the spatial disparity between the 13 semi-separated sub-lakes. Based on samples of 35 sampling sites collected before, in the middle, and at the end of ice-on season separately, we performed a quantitative analysis of under-ice lake N accumulation and water-sediment N exchange by analyzing N fraction variations. Hierarchical Cluster Analysis and Relevance Analysis were used to help elucidate the main causes and implications of under-ice N variation. Our results clearly show that existing studies have underestimated the impact of under-ice N accumulation on the lake ecology throughout year: 1) Sediment N accumulated 2-3 times more than that before winter; 2) residual nitrogen (Res-N) contributed to the majority of the accumulated sediment N and was mainly induced by the debris of macrophytes; 3) total available nitrogen (TAN) was the most easily exchanged fractions between sediment and water, and it mainly affected the water environment during winter; 4) the Res-N accumulation during the ice-on season may have a strong impact on the eco-environment in the subsequent seasons. Our research is valuable for understanding the mechanism of internal nutrient cycle and controlling the internal nitrogen pollution, especially in shallow seasonally-frozen lakes that have long suffered from macrophyte-phytoplankton co-dominated eutrophication.

Safety and efficacy of oral nemonoxacin versus levofloxacin in treatment of community-acquired pneumonia: A phase 3, multicenter, randomized, double-blind, double-dummy, active-controlled, non-inferiority trial.

BACKGROUND/PURPOSE: Nemonoxacin is a novel nonfluorinated quinolone with excellent in vitro activity against most pathogens in community-acquired pneumonia (CAP), especially Gram-positive isolates. The purpose of this study was to assess the efficacy and safety of nemonoxacin compared with levofloxacin in patients with CAP. METHODS: A phase 3, multicenter, randomized (2:1) controlled trial was conducted in adult CAP patients receiving nemonoxacin 500 mg or levofloxacin 500 mg orally once daily for 7-10 days. Clinical, microbiological response and adverse events were assessed. Non-inferiority was determined in terms of clinical cure rate of nemonoxacin compared with that of levofloxacin in a modified intention-to-treat (mITT) population. NCT registration number: NCT01529476. RESULTS: A total of 527 patients were randomized and treated with nemonoxacin (n = 356) or levofloxacin (n = 171). The clinical cure rate at test-of-cure visit was 94.3% (300/318) for nemonoxacin and 93.5% (143/153) for levofloxacin in the mITT population [difference (95% CI), 0.9% (-3.8%, 5.5%)]. The microbiological success rate was 92.1% (105/114) for nemonoxacin and 91.7% (55/60) for levofloxacin in the bacteriological mITT population [difference (95% CI), 0.4% (-8.1%, 9.0%)]. The incidence of adverse events (AEs) was comparable between nemonoxacin (33.1%, 118/356) and levofloxacin (33.3%, 57/171) (P > 0.05). CONCLUSION: Nemonoxacin 500 mg once daily for 7-10 days is as effective and safe as levofloxacin for treating adult CAP patients in terms of clinical cure rates, microbiological success rates, and safety profile. ClinicalTrials.gov identifier: NCT01529476.

Optimization of linezolid treatment regimens for Gram-positive bacterial infections based on pharmacokinetic/pharmacodynamic analysis.

AIM: To optimize linezolid treatment regimens for Gram-positive bacterial infections based on pharmacokinetic/pharmacodynamic analysis. MATERIALS & METHODS: The minimum inhibitory concentration (MIC) distribution of 572 Gram-positive strains from patients with clinically confirmed infections was analyzed. Using the Monte Carlo simulation method, the cumulative fraction of response and probability of target attainment were determined for linezolid regimens of 600 mg q.12h and q.8h Results: Linezolid dosage of 600 mg q.12h yielded >90% cumulative fraction of response and probability of target attainment for staphylococcal infections with an MIC of ≤1 mg/l, enterococcal infections with higher MIC values required 600 mg q.8h. CONCLUSION: Linezolid 600 mg q.12h is still the clinically recommended empirical dosage for Gram-positive bacterial infections. However, as bacterial MICs increase, 600 mg q.8h may be required to achieve better efficacy.