Antibiotic resistant genes profile in the surface water of subtropical drinking water river-reservoir system.

To comprehensively understand antibiotic resistant genes (ARGs) profile in the subtropical drinking water river-reservoir system, this study selected Dongzhen river-reservoir system in Mulan Creek as object to investigate the spatial-temporal characteristics of ARGs diversity, bacterial host and resistance mechanism, and to analyze the key environmental factors driving ARGs profile variation. The results indicated that a total of 440 ARGs were detected in the target system, and the ARGs distribution pattern in the reservoir was attributed to autologous evolution or the comprehensive influence of feeding river system. The predominant bacterial host at different sites showed similar variations to dominated ARGs, and Proteobacteria, Actinobacteria and Bacteroidetes harbored most ARGs at phylum level, which showed the highest proportions of 74%, 37% and 35%, respectively. Antibiotic efflux was the primary resistance mechanism in all samples from wet season (45%-60%), yet the samples from dry season exhibited multiple resistance mechanisms, including inactivation (37%-52%), efflux (44%), and target alteration (43%). The total relative abundances of ARGs in the target system ranged from 0.89 × 10-2 to 1.71 × 10-2, and seasonal variation had a more significant influence on ARGs abundance than spatial variation (R = 0.68, P < 0.01). Environmental factors analysis indicated that the concentrations of nitrite nitrogen and total organic carbon were significant factors explaining ARGs number and various resistance mechanism proportions (P < 0.01), accounting for 48.7% and 61.1% of the variation, respectively; ammonia nitrogen concentration, total organic carbon concentration, temperature and pH were the significant influence factors on the relative abundance of ARGs (P < 0.05), with standardized regression weights of 0.700, 1.414, 1.447, and 1.727, respectively. In summary, in the surface water of the target system, ARGs diversity was primarily driven by ARGs horizontal transfer and antibiotics biosynthesis. Nutrients mainly promoted ARGs abundance by providing abundant energy, rather than increasing bacterial reproductive capacity.

Planktonic microbial community and biological metabolism in a subtropical drinking water river-reservoir system.

To understand the dynamics of planktonic microbial community and its metabolism processes in subtropical drinking water river-reservoir system with lower man-made pollution loading, this study selected Dongzhen river-reservoir system in Mulan Creek as object to investigate spatial-temporal characteristics of community profile and functional genes involved in biological metabolism, and to analyze the influence of environmental factors. The results indicated that Proteobacteria and Actinobacteria were the most diverse phyla with proportion ranges of 9%-80% in target system, and carbohydrate metabolism (5.76-7.12 × 10-2), amino acid metabolism (5.78-7.21 × 10-2) and energy metabolism (4.07-5.17 × 10-2) were found to be the dominant pathways of biological metabolism. Although there were variations in biological properties both spatially and temporally, seasonal variation had a greater influence on microbial community and biological metabolism, than locational differences. Regarding the role of environmental factors, this study revealed that microbial diversity could be affected by multiple abiotic factors, with total organic carbon, total phosphorus and temperature being more influential (absolute value of standardized regression weights >2.13). Stochastic processes dominated the microbial community assembly (R2 of neutral community model = 0.645), while niche-based processes differences represented by nutrients, temperature and pH level played secondary roles (R > 0.388, P < 0.01). Notably, the synergistic influences among the environmental factors accounted for the higher percentages of community variation (maximum proportion up to 17.6%). Additionally, pH level, temperature, and concentrations of dissolved oxygen, carbon and nitrogen were found to be the significant factors affecting carbon metabolism pathways (P < 0.05), yet only total organic carbon significantly affected on nitrogen transformation (P < 0.05). In summary, the microbial profile in reservoir is not completely dominated by that in feeding river, and planktonic microbial community and its metabolism in subtropical drinking water river-reservoir system are shaped by multiple abiotic and biotic factors with underlying interactions.

A phase III study of late course accelerated hyperfractionated radiotherapy versus conventionally fractionated radiotherapy in patients with nasopharyngeal carcinoma.

OBJECTIVE: To compare the efficacy and toxicity of late course accelerated hyperfractionated radiotherapy (LCAF) with conventionally fractionated (CF) radiotherapy in the treatment of nasopharyngeal carcinoma (NPC). METHODS: Between March 1998 and November 2002, 200 eligible patients with NPC were randomized to receive either LCAF (48 Gy in 40 fractions, 2 fractions per day, 1.2 Gy/fraction, with an interval of ≥6 h, 5 d/wk, followed by 30 Gy in 20 fractions using 2 fractions per day, 1.5 Gy/fraction, 5 d/wk) or CF (35 fractions, 2.0 Gy/fraction/d, 5 d/wk, to a total dose of 70 Gy). RESULTS: All patients completed the treatment. Overall baseline characteristics of the study population of the 2 arms were well balanced. With a median follow-up of 6.9 years, the 5-year local control rate was higher in the LCAF arm (87.6% vs. 75.9%, P=0.044). The 5-year overall survival rates were 74.1% vs. 58.0% (P=0.024) for the LCAF arm and the CF arm, respectively. LCAF patients had a higher occurrence of acute mucositis and a more evident weight loss than CF patients, whereas incidence rates of radiation-induced damage to the central nervous system were similar in the 2 arms. CONCLUSIONS: LCAF achieved higher local control and overall survival rates than CF radiotherapy, without increasing radiation-related late complications such as cranial nerve palsy.

The in vivo study on the radiobiologic effect of prolonged delivery time to tumor control in C57BL mice implanted with Lewis lung cancer.

BACKGROUND: High-precision radiation therapy techniques such as IMRT or sterotactic radiosurgery, delivers more complex treatment fields than conventional techniques. The increased complexity causes longer dose delivery times for each fraction. The purpose of this work is to explore the radiobiologic effect of prolonged fraction delivery time on tumor response and survival in vivo. METHODS: 1-cm-diameter Lewis lung cancer tumors growing in the legs of C57BL mice were used. To evaluate effect of dose delivery prolongation, 18 Gy was divided into different subfractions. 48 mice were randomized into 6 groups: the normal control group, the single fraction with 18 Gy group, the two subfractions with 30 min interval group, the seven subfractions with 5 min interval group, the two subfractions with 60 min interval group and the seven subfractions with 10 min interval group. The tumor growth tendency, the tumor growth delay and the mice survival time were analyzed. RESULTS: The tumor growth delay of groups with prolonged delivery time was shorter than the group with single fraction of 18 Gy (P < 0.05). The tumor grow delay of groups with prolonged delivery time 30 min was longer than that of groups with prolonged delivery time 60 min P < 0.05). There was no significant difference between groups with same delivery time (P > 0.05). Compared to the group with single fraction of 18 Gy, the groups with prolonged delivery time shorten the mice survival time while there was no significant difference between the groups with prolonged delivery time 30 min and the groups with prolonged delivery time 60 min. CONCLUSIONS: The prolonged delivery time with same radiation dose shorten the tumor growth delay and survival time in the mice implanted with Lewis lung cancer. The anti-tumor effect decreased with elongation of the total interfractional time.

Late course accelerated hyperfractionated radiotherapy of nasopharyngeal carcinoma (LCAF).

BACKGROUND AND PURPOSE: To study the efficacy of late course accelerated fractionated (LCAF) radiotherapy in the treatment of nasopharyngeal carcinoma (NPC). The end-points were local control, radiation-induced complications, and factors influencing survival. PATIENTS AND METHODS: Between December 1995 and April 1998, 178 consecutive NPC patients were admitted for radiation treatment. The radiation beam used was (60)Co gamma or 6 MV X rays. For the first two-thirds of the treatment, two daily fractions of 1.2 Gy were given to the primary lesion, with an interval of > or =6h, 5 days per week to a total dose of 48 Gy/40 fractions, over a period of 4 weeks. For the last third of the treatment, i.e., beginning the 5th week of treatment, an accelerated hyperfractionated schedule was carried out. The dose per fraction was increased to 1.5 Gy, 2 fractions per day with an interval of > or =6h, the total dose for this part of the protocol was 30 Gy/20 fractions over 2 weeks. Thus the total dose was 78 Gy in 60 fractions in 6 weeks. RESULTS: All patients completed the treatment. Acute mucositis: none in 2 cases, Grade 1 in 43 cases, Grade 2 in 78 cases, Grade 3 in 52 cases, and Grade 4 in 3 cases. Local control rate: the 5 year nasopharyngeal local control rate was 87.7%, and the cervical lymph nodes local control rate was 85.7%. The 5-year distant metastasis rate was 26.1%, and 5 year survivals were 67.9%, 16 (9%) patients had radiation-induced cranial nerve palsy, 7(4%) patients had temporal lobe or brainstem damage. CONCLUSIONS: With this treatment schedule, patients' tolerance was good, local control and 5 year survivals were better than conventional fractionation schedules, and radiation-related late complications did not increase, as 5-year survival rates of conventional fractionation radiotherapy were only 58%. Randomized clinical trials are being carried out to further confirm the efficacy of LCAF for nasopharyngeal carcinoma.

Comparison between continuous accelerated hyperfractionated and late-course accelerated hyperfractionated radiotherapy for esophageal carcinoma.

PURPOSE: To compare the treatment results and toxicity of continuous accelerated hyperfractionated (CAHF) and late-course accelerated hyperfractionated (LCAF) radiotherapy (RT) for esophageal carcinoma. METHODS AND MATERIALS: Between August 1996 and March 1999, 101 patients with squamous cell carcinoma of the esophagus were randomized into two groups: 49 to the CAHF group and 52 to the LCAF group. Patients in the CAHF group received RT at 1.5 Gy/fraction b.i.d. (6-h interval), 5 d/wk, to a total dose 66 Gy in 44 fractions during 4.4 weeks. The patients in the LCAF group received conventional fractionation RT, 1.8 Gy/fraction, to a dose of 41.4 Gy in 23 fractions during 4.6 weeks, followed by accelerated fractionation RT using reduced fields, b.i.d., at 1.5 Gy/fraction, with a minimal interval of 6 h between fractions. The total dose was 68.4 Gy in 41 fraction during 6.4 weeks. Patient age, gender, performance score, diet, lesion location, lesion length, stage, and fractionation (CAHF or LCAF) were entered into the univariate and multivariate analyses. RESULTS: All patients finished the treatment course, except for 1 patient in the CAHF group because of severe acute esophagitis. The rate of Grade I, II, and III acute bronchitis was 18.4% (9 of 49), 30.6% (15 of 49), and 8.2% (4 of 49) in the CAHF group and 13.5% (7 of 52), 21.2% (11 of 52), and 3.8% (2 of 52) in the LCAF group, respectively. However, the difference between the two groups was not statistically significant (p = 0.084). The rate of Grade I, II, III, and IV acute esophagitis was 6.1% (3 of 49), 32.7% (16 of 49), 46.9% (23 of 49), and 14.3% (7 of 49) in the CAHF group and 26.9% (14 of 52), 32.7% (17 of 52), 7.7% (4 of 52), and 1.9% (1 of 52) in the LCAF group, respectively. The difference was statistically significant (p < 0.001). The local control rate at 1, 2, and 3 years was 88.7%, 83.9%, and 55.9% in the CAHF group and 80.7%, 71.4%, and 57.1% in the LCAF group, respectively (p = 0.1251). The 1-, 2-, and 3-year survival rate was 79.6%, 51.6%, and 37.6% in the CAHF group and 80.0%, 57.6%, and 41.2% in the LCAF group, respectively (p = 0.5757). Multivariate analysis showed that age and lesion length were independent significant prognostic factors for local control rate, and age was for the overall survival rate. The fractionation schedule had no significant prognostic effect. CONCLUSION: CAHF and LCAF result in similar 1-, 2-, and 3-year local control and survival rates. CAHF resulted in more severe acute esophagitis and may be less well tolerated than LCAF. The treatment results after the CAHF and LCAF regimens were better than those of historical conventional RT.