Integrated soil-crop system management for food security.

China and other rapidly developing economies face the dual challenge of substantially increasing yields of cereal grains while at the same time reducing the very substantial environmental impacts of intensive agriculture. We used a model-driven integrated soil-crop system management approach to develop a maize production system that achieved mean maize yields of 13.0 t ha(-1) on 66 on-farm experimental plots--nearly twice the yield of current farmers' practices--with no increase in N fertilizer use. Such integrated soil-crop system management systems represent a priority for agricultural research and implementation, especially in rapidly growing economies.

[Cell death of THP-1 induced by puried Rv3671c protein of tuberculosis and the detection of TNF-α and IL-1ß in Mycobacterium tuberculosis].

OBJECTIVE: To assess the response in THP-1 treated with Rv3671c protein in Mycobacterium tuberculosis (M.tuberculosis). METHODS: The gene encoding Rv3671c protein of M.tuberculosis was cloned into pET-28a vector and then expressed in Escherichia coli. The Rv3671c was purified with Ni-NTA affinity and ion exchange chromatography. The detection of protein concentration was by Lowry method.THP-1 cell was stimulated with Rv3671c protein and cells were analyzed by Hochest staining under fluorescence microscopy to assay cell death (apoptosis and necrosis). TNF-α and IL-1ß were detected by ELISA at each stimulating time. RESULTS: The Rv3671c protein of M.tuberculosis was successfully expressed in Escherichia coli. The purity of recombinant Rv3671c protein was 95%, and the protein concentration was up to 0.4 mg/ml. The nucleus of THP-1 was isolated and necrosis-like under fluorescence when cells were stimulated by Rv3671c protein. The levels of TNF-α and IL-1ß in supernatant were 19 000 and 16 500 pg/ml respectively, and were significantly higher than control cells with the levels of 2100 and 3800 pg/ml separately. CONCLUSION: The necrosis of THP-1 cells could be stimulated by Rv3671c protein of M.tuberculosis and it was probably associated with high cytokines TNF-α and IL-1ß levels.

Biofortification of different maize cultivars with zinc, iron and selenium by foliar fertilizer applications.

Fertilizer-based biofortification is a strategy for combating worldwide malnutrition of zinc (Zn), iron (Fe) and selenium (Se). Field experiments were conducted to investigate the effects of foliar treatments on concentrations of Zn, Fe, Se, N and bioavailability of Zn and Fe in grains of three maize cultivars grown at three locations. We compared the efficacy of ZnO nanoparticles (ZnO-NPs), Zn complexed chitosan nanoparticles (Zn-CNPs), conventional ZnSO4 and a cocktail solution (containing Zn, Fe and Se). All treatments were foliar-applied at rate of 452 mg Zn L-1, plus urea. Applying ten-fold less Zn (at rate of 45.2 mg Zn L-1) plus urea in the form of ZnO-NPs, Zn-CNPs, or ZnSO4 resulted in no increase, or a negligible increase, in grain Zn concentration compared with deionized water. By contrast, among the different Zn sources plus urea applied by foliar sprays, conventional ZnSO4 was the most efficient in improving grain Zn concentration. Furthermore, foliar application of a cocktail solution effectively improved grain concentrations of Zn, Fe, Se and N simultaneously, without a grain yield trade-off. For example, the average grain concentrations were simultaneously increased from 13.8 to 22.1 mg kg-1 for Zn, from 17.2 to 22.1 mg kg-1for Fe, from 21.4 to 413.5 ug kg-1 for Se and from 13.8 to 14.7 g kg-1 for N by foliar application of a cocktail solution. Because grain yield was significantly negatively correlated with grain nutrient concentrations, the magnitude of increase in grain concentrations of Zn and Fe was most pronounced in the maize cultivar with the lowest grain yield (Zhengdan958 grown in Linyi). Foliar application of a cocktail solution also significantly decreased the phytic acid (PA) concentration, ratios of PA/Fe and PA/Zn in grains, indicating an increased bioavailability of Fe and Zn for human health. In conclusion, we found that a foliar application of a cocktail solution including Zn, Fe, Se and N was most effective for biofortification, but that the grains with the lowest yield contained the greatest concentration of these elements. This finding highlights the need to breed maize varieties that are capable of achieving both high grain yield and high grain nutritional quality to address food security and human health challenges.

Reducing environmental risk by improving N management in intensive Chinese agricultural systems.

Excessive N fertilization in intensive agricultural areas of China has resulted in serious environmental problems because of atmospheric, soil, and water enrichment with reactive N of agricultural origin. This study examines grain yields and N loss pathways using a synthetic approach in 2 of the most intensive double-cropping systems in China: waterlogged rice/upland wheat in the Taihu region of east China versus irrigated wheat/rainfed maize on the North China Plain. When compared with knowledge-based optimum N fertilization with 30-60% N savings, we found that current agricultural N practices with 550-600 kg of N per hectare fertilizer annually do not significantly increase crop yields but do lead to about 2 times larger N losses to the environment. The higher N loss rates and lower N retention rates indicate little utilization of residual N by the succeeding crop in rice/wheat systems in comparison with wheat/maize systems. Periodic waterlogging of upland systems caused large N losses by denitrification in the Taihu region. Calcareous soils and concentrated summer rainfall resulted in ammonia volatilization (19% for wheat and 24% for maize) and nitrate leaching being the main N loss pathways in wheat/maize systems. More than 2-fold increases in atmospheric deposition and irrigation water N reflect heavy air and water pollution and these have become important N sources to agricultural ecosystems. A better N balance can be achieved without sacrificing crop yields but significantly reducing environmental risk by adopting optimum N fertilization techniques, controlling the primary N loss pathways, and improving the performance of the agricultural Extension Service.

[Cross-resistance between rifampin and rifabutin in multidrug resistant Mycobacterium tuberculosis complex strains].

OBJECTIVE: To study the cross-resistance between rifampin and rifabutin in multidrug resistant Mycobacterium tuberculosis complex strains, and therefore to provide laboratory data for using rifabutin in the treatment of multidrug resistant tuberculosis. METHODS: The MIC(90) of rifabutin and rifampin against 99 multidrug resistant Mycobacterium tuberculosis clinical strains were determined by microplate assays. Statistical analysis was performed by using the χ(2) test and the t test. RESULTS: The cross-resistance rate between rifampicin and rifabutin was 85.9% (85/99), but the MIC(90) of rifabutin (≤ 16 mg/L, median 2 mg/L) was significantly lower than that of rifampicin (≥ 2 mg/L, median > 32 mg/L). The cross-resistance rate increased with the resistance level of rifampicin. The cross-resistance strains in the lower and the medium groups were 0/9 and 5/9 respectively, while the strains of the high rifampicin-resistant group were almost all cross-resistant (98.8%, 80/81). CONCLUSION: Rifabutin had activities against rifampin resistant Mycobacterium tuberculosis complex strains in vitro, and therefore may be used as an alternative for the treatment of multidrug resistant tuberculosis.

[Fast identification of mycobacteria in microtiter liquid culture].

OBJECTIVE: This research was to establish a method for fast identification of mycobacteria in microtiter liquid culture and to evaluate its clinical value. METHODS: 2-thiophenecarboxylic acid hydrazide (TCH) and paranitrobenzoic acid (PNB) at different concentrations were added into liquid culture in 96-well plate. Different mycobacterium standard strains were incubated in liquid culture with PNB and TCH for 7 to 10 days. According to the growth assay for 15 mycobacterium strains and 30 mycobacterium tuberculosis strains, the best PNB and TCH concentration were determined. A total of 424 clinical mycobacterium isolates were identified by microtiter liquid culture at the best PNB and TCH concentration. The results of microtiter liquid culture were compared with those of PCR and DNA sequencing. RESULTS: The best concentration of PNB was 200 µg/ml in microtiter liquid culture. Compared with the results of PCR, the sensitivity and specificity for identification of mycobacterium tuberculosis complex in microtiter liquid culture were 97.8% (306/313) and 100.0% (107/107) respectively and those for non-tuberculosis mycobacteria in microtiter liquid culture were 100.0% (107/107) and 96.5% (306/317) respectively. The best concentration of TCH was 0.5 µg/ml. Compared with the results of PCR, the sensitivity of mycobacterium tuberculosis in microtiter liquid culture was 100.0% (305/305). The specificity remained under and more studies were needed. CONCLUSION: In microtiter liquid culture with PNB and TCH, mycobacteria can be identified in 7 to 10 days. The results were accurate and the process was simple without expensive equipments. This method meets clinical needs and can be used in all level hospitals in China.

[Evaluation of microscopic observation drug susceptibility for drug susceptibility testing of mycobacterium tuberculosis in smear-positive sputum].

OBJECTIVE: To evaluate microscopic observation drug susceptibility (MODS) for mycobacterium tuberculosis drug susceptibility in smear-positive sputum. METHODS: Drug susceptibility of mycobacterium tuberculosis in 275 smear-positive sputum samples collected from TB patients were detected directly by MODS. The susceptibility of seven antimicrobials including streptomycin, isoniazid, rifampicin, ethambutol, levofloxacin, amikacin and capromycin were detected MODS. At the same time the sputum sample were cultured in MGIT 960 tube and the positive isolates were tested for drug susceptibility by MGIT 960 system. The results of MODS were analyzed and compared with that of MGIT 960. RESULTS: Of 275 smear-positive sputum, MODS detected 235 (85.45%). Results of MODS were obtained in a median time of 18 days (5 - 39 d). For the 235 MODS-positive samples, the compliance rates of MODS to MGIT of 7 drugs were 90.21% (212/235), 88.09% (207/235), 93.62% (220/235), 87.23% (205/235), 92.34% (217/235), 88.51% (208/235) and 86.81% (204/235) respectively. The sensitivity of MODS method were 83.33% (90/108), 85.11% (120/141), 90.74% (98/108), 85.71% (78/91), 86.73% (85/98), 76.92% (40/52) and 77.08% (37/48). The specificities of MODS method were 96.06% (122/127), 92.55% (87/94), 96.06% (122/127), 88.19% (127/144), 96.35% (132/137), 91.80% (168/183) and 89.30% (167/187) respectively. CONCLUSION: MODS is an optimal alternative method for direct and rapid drug susceptibility of sputum with high accuracy in a timely and affordable way in resource-limited settings.

[Evaluation of the isothermal RNA amplification assay for Mycobacterium tuberculosis in sputum samples].

OBJECTIVE: To evaluate the use of isothermal RNA amplification assay for detection of Mycobacterium tuberculosis (SAT-TB) in sputum samples. METHODS: A total of 244 sputum samples from patients with pulmonary tuberculosis and those with other lung diseases were detected by SAT-TB and Lowenstein-Jensen (L-J) culture. The samples with different results between SAT-TB and L-J culture were tested by Mycobacterium tuberculosis PCR fluorescence diagnostic kits. The sensitivity and specificity of SAT-TB were calculated according to the results of L-J culture. The detection rates of SAT-TB and L-J culture were analyzed according to the clinical diagnosis and the difference of the 2 methods were analyzed by chi-square test. RESULTS: With the result of L-J culture as the reference, the sensitivity and the specificity of SAT-TB were 92% (71/77) and 86% (143/167), respectively. The accordance rate of SAT-TB and L-J culture was 88% (214/244). For tuberculosis patients, the detection rate of L-J culture and SAT-TB was 42% (75/177) and 54% (95/177) respectively. The difference between the detection rates of SAT-TB and L-J was significant by chi-square test (χ² = 4.527, P < 0.05). CONCLUSIONS: SAT-TB is a rapid, sensitive and specific method for detection of Mycobacterium tuberculosis in clinical sputum samples.

[In vitro activities of clofazimine against different drug-resistant types of Mycobacterium tuberculosis].

OBJECTIVE: To study the in vitro antituberculous activities of clofazimine (CLF) to different drug-resistant types of Mycobacterium tuberculosis. METHODS: The minimal inhibitory concentration (MIC) of CLF and isoniazid (INH), rifampicin (RFP), ofloxacin (OFLX), amikacin (AK), and capreomycin (CPM) against sensitive, single-drug resistant (SDR), poly-drug resistant (PDR), multi-drug resistant (MDR), and extensive-drug resistant (XDR) Mycobacterium tuberculosis strains isolated clinically were determined by microplate assays. RESULTS: The MICs of CLF for sensitive, SDR, PDR, MDR and XDR strains of clinically isolated Mycobacterium tuberculosis were 0.06 - 4.00 mg/L, 0.03 - 4.00 mg/L, 0.06 - 8.00 mg/L, 0.06 - 8.00 mg/L, 0.03 - 8.00 mg/L. For the sensitive group, the MIC of CLF (0.06 - 4.00 mg/L) was higher than that of INH (0.06 - 0.25 mg/L) and RFP (0.06 - 0.25 mg/L), while there was no significant difference among OFLX (0.06 - 2.00 mg/L), AK (0.06 - 4.00 mg/L), and CPM (0.50 - 4.00 mg/L). For the single-drug resistant group, there was no significant difference among CLF (0.03 - 4.00 mg/L), INH (0.06 - 0.25 mg/L), and RFP (0.06 - 0.25 mg/L), but the MIC of CLF was lower than that of OFLX (0.25 - 8.00 mg/L), AK (0.06 - 4.00 mg/L), and CPM (0.50 - 8.00 mg/L). For the MDR group, there was no significant difference between CLF (0.06 - 8.00 mg/L) and AK (0.25 - 8.00 mg/L), but the MIC of CLF was lower than that of OFLX (0.125 - 8.00 mg/L) and CPM (0.50 - 8.00 mg/L). For the XDR group, the MIC of CLF (0.03 - 8.00 mg/L) was lower than that of others. CONCLUSION: CLF showed good in vitro activity against Mycobacterium tuberculosis, especially MDR and XDR strains.

[Screening of the binding peptides of Mycobacterium tuberculosis H(37)Rv].

OBJECTIVE: To screen the Mycobacterium tuberculosis H(37)Rv binding peptide using phage-displayed random peptide libraries, and to analyze the binding capacity of the peptide with Mycobacterium tuberculosis. METHODS: Inactive Mycobacterium tuberculosis H(37)Rv was used for screening of the binding peptide from the Ph.D.-7 peptide library, and Mycobacterium smegmatis was used for reverse screening during the 2(nd) to 4(th) rounds of screening. After 4 rounds of screening, single phages were randomly selected for DNA sequencing. The selected clones were tested by indirect enzyme linked immunosorbent assay (ELISA). The peptide of positive clone, which showed the highest affinity, was synthesized in vitro with fluorescent markers. The specific combination of the peptide with 16 mycobacterium standard strains and 3 other microbes (Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans) were observed by fluorescence microscopy. RESULTS: After 4 rounds of biopanning, remarkable enrichment of the phages that specifically bind with target molecules were observed. Single phages were randomly selected for sequencing analysis and 5 sequences were obtained. Five phages with different sequences were detected using indirect ELISA and all of them were found to be positive clones. Phage 8 showed the highest affinity with target molecule. The peptide of phage H8 was synthesized in vitro with fluorescent markers, and it was confirmed that the peptide could bind with H(37)Rv and other 15 mycobacterium including Mycobacterium smegmatis, but not with 3 other microbes. CONCLUSIONS: By using phage-displayed random peptide libraries, we obtained the binding peptide of H(37)Rv. It was shown that the peptide could bind with Mycobacterium tuberculosis specifically, which provided a new way for the detection of Mycobacterium tuberculosis in vitro.

[Monitoring winter wheat population dynamics using an active crop sensor].

Tiller density plays an important role in attaining optimum grain yield and applying topdressing N in winter wheat. However, the traditional approach based on determining tiller density is time-consuming and labor-intensive. As technology advances, remote sensing might provide an opportunity in eliminating this7 problem. In the present paper, an N rate experiment and a variety-seeding and sowing dates experiment were conducted in Quzhou County, Hebei Province in 2008/2009 to develop the models to predict the amount of winter wheat tillers. Positive linear relationships between vegetation indices and tillers were observed across growth stages (R2, 0.25-0.64 for NDVI; 0.26-0.65 for RVI). The validation results indicated that the prediction using NDVI had the higher coefficient of determination (R2, 0.54-0.64), the lower root mean square error (RMSE, 260-350 tillers m(-2)) and relative error (RE, 16.3%-23.0%) at early growth stages of winter wheat. We conclude that active GreenSeeker sensor is a promising tool for timely monitoring of winter wheat tiller density.

[The effects of gene mutation related to drug resistance and drug efflux pump in extensively drug-resistant tuberculosis clinical isolates].

OBJECTIVE: To explore the effects of 2 major drug-resistant mechanisms in clinically isolated strains of extensively drug-resistant tuberculosis (XDR-MTB). METHODS: Genomic DNA of 10 XDR-MTB strains isolated from Shanghai Pulmonary Hospital were extracted. The main gene mutations related to drug resistance and 15 SNPs unique to XDR-MTB clinical isolate KZN605 reported by the Broad Institute in USA were detected by sequencing. The changes of minimal inhibition concentration (MIC) of XDR-MTB isolates were detected before and after the addition of efflux pump inhibitors verapamil, CCCP and reserpine in liquid cultures. RESULTS: The mutation of rpoB, katG and rpsL occurred in all XDR-MTB strains. The mutation of gyrA, gyrB and rrs occurred in 9 strains, 2 strains and 6 strains respectively. There was no mutation of tlyA in all the strains. Most of the SNPs in KZN 605 strains were not detected in the clinical strains. The clinical strains showed no significant changes of MICs, except 1 strain for which the MIC of ofloxacin decreased by 16 times after addition of the efflux pump inhibitors. CONCLUSIONS: The gene mutations related to drug resistance are the key mechanism for the clinical XDR-MTB strains, while the efflux pumps partly play a role in the drug resistance to fluoroquinolones. The detailed mechanism of efflux pump mediated drug resistance to other anti-TB drugs needs further study.

[Identification of the Mycobacterium tuberculosis complex by detecting recombinant secretory protein MPT64].

OBJECTIVE: To identify the Mycobacterium tuberculosis complex by detecting the secretory protein MPT64. METHODS: The gene mpt64 was amplified by polymerase chain reaction (PCR) from the genome of Mycobacterium tuberculosis H(37)Rv strain and cloned into expression vector. Immune sera from rabbits by recombinant proteins MPT64, were used to make enzyme-labeled antibodies and coated antibodies. A double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was established to detect the secretory protein MPT64 of the culture supernatants in Mycobacterium strains. Results of ELISA were compared to those of the gene mpt64 amplified by PCR. RESULTS: A recombinant vector was constructed. The minimum detectable concentration of MPT64 was 0.01 mg/L. A total of 27 reference strains and 170 clinical isolate strains were evaluated. PCR for Mycobacterium tuberculosis reference strain, Mycobacterium bovis reference strain and Mycobacterium africanum reference strain was positive, but that for other reference stains was negative, consistent with the results of ELISA. In the 170 clinical isolate stains, the positive result of PCR and ELISA was 98.2% (111/113) and 97.3% (110/113) respectively, while the specificity of PCR and ELISA was both 100%, no positive result in non-tuberculosis mycobacterium strains. CONCLUSION: Identification of the Mycobacterium tuberculosis complex by detecting secretory protein MPT64 is rapid, sensitive, and specific, which can be used routinely in clinical laboratories.

Harvesting more grain zinc of wheat for human health.

Increasing grain zinc (Zn) concentration of cereals for minimizing Zn malnutrition in two billion people represents an important global humanitarian challenge. Grain Zn in field-grown wheat at the global scale ranges from 20.4 to 30.5 mg kg-1, showing a solid gap to the biofortification target for human health (40 mg kg-1). Through a group of field experiments, we found that the low grain Zn was not closely linked to historical replacements of varieties during the Green Revolution, but greatly aggravated by phosphorus (P) overuse or insufficient nitrogen (N) application. We also conducted a total of 320-pair plots field experiments and found an average increase of 10.5 mg kg-1 by foliar Zn application. We conclude that an integrated strategy, including not only Zn-responsive genotypes, but of a similar importance, Zn application and field N and P management, are required to harvest more grain Zn and meanwhile ensure better yield in wheat-dominant areas.

[A study of the bacteriophage-based assay for the detection of pyrazinamide resistance in Mycobacterium tuberculosis].

OBJECTIVE: To set up and evaluate the method of phage amplified biologically assay (PhaB) in rapid detection of pyrazinamide (PZA) resistance. METHODS: The PhaB assay was developed and applied in detecting PZA resistance in 108 clinical isolates of Mycobacterium tuberculosis and the results were compared with those of the absolute concentration method. The minimum inhibitory concentration (MIC) was detected for all discrepancy isolates. RESULTS: The results showed that the optimal detecting condition was pH 5.5, PZA 200 microg/ml and 48 h. Of the 108 strains of Mycobacterium tuberculosis, 28 strains were PZA-susceptible and 80 strains were PZA-resistant detected by PhaB; while 32 strains were PZA-susceptible and 76 strains were PZA-resistant by absolute concentration method. Twenty-eight of the 108 strains were PZA-susceptible and 71 were PZA-resistant by the two methods. The concordant isolates of determination of PZA resistance were 99 by the two methods and the concordance rates was 91.7%. There were 9 strains in discordant isolates, of which 7 were the same with MIC method and gene chip in drug susceptibility. If the results of absolute concentration method was the gold standard, the sensitivity, specificity, positive and negative predictive values, as well as accuracy of PhaB assay was 94.7%, 84.8%, 93.4%, 87.5% and 91.7% respectively. CONCLUSION: The PhaB assay can be used as a rapid screening method for detection of drug susceptibility of PZA in clinical isolates of Mycobacterium tuberculosis.

[Comparison between bacteriophage-based assay and BACTEC-960 system in detection of ethambutol resistance in Mycobacterium tuberculosis].

OBJECTIVE: To set up phage amplified biologically assay (PhaB) for rapid detection ethambutol (EMB) resistance and to evaluate the use of PhaB in the detection of EMB resistance. METHODS: To detect the EMB resistance of 138 clinical isolates of Mycobacterium tuberculosis (MTB) by PhaB and compare it with the results of BACTEC-960 system. The minimal inhibitory concentration (MIC) was detected for all the discrepant isolates. RESULTS: Of all the 138 strains of MTB clinical isolates, 114 strains were EMB-susceptible and 24 strains were EMB-resistant with BACTEC-960 system while 118 strains were EMB-susceptible and 20 strains were EMB-resistant with PhaB. 112 of the 138 strains were EMB-susceptible and 18 strains were EMB-resistant with the two methods. The concordant isolates in determination of EMB resistance were 130 strains in the two methods and the concordance rate was 94.2%. The disconcordant isolates were 8 strains and the discrepancy rate was 5.8%. The sensitivity, specificity, positive and negative predictive value as well as overall accuracy for the PhaB assay was 75.0% (18/24), 98.2% (112/114), 90.0% (18/20), 94.9% (112/118) and 94.2% (130/138) respectively if the judgment standard was adopted by BACTEC-960 method. CONCLUSIONS: The PhaB assay can be used for detection of EMB resistance in isolates of MTB easily and quickly in three days. This method do not need special instrument and may be used in rapid screening method for EMB resistance of MTB.

[Comparison of four methods in the detection of isoniazid resistance in clinical isolates of Mycobacterium tuberculosis].

OBJECTIVE: To evaluate the use of phage amplified biologically (PhaB) assay, Bactec-960 system, minimum inhibitory concentration (MIC) method and gene chip in drug susceptibility testing of isoniazid (INH) in clinical isolates of Mycobacterium tuberculosis (MTB). METHODS: INH resistance of 167 clinical isolates of MTB was detected by PhaB assay, Bactec-960 system, MIC and gene-chip methods respectively, and the results of these four methods were compared. RESULTS: 111 INH resistant isolates and 56 INH sensitive isolates were detected by Bactec-960 system. If the result of Bactec-960 system was set as the golden standard, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of PhaB assay were 96.4%, 96.4%, 93.1%, 98.2%, and 96.4% respectively; the sensitivity, specificity, PPV, NPV, and accuracy were 92.9%, 99.1%, 98.1%, 96.5%, and 97.0% for the MIC method, and they were 83.9%, 96.4%, 92.2%, 92.2%, and 92.2% respectively for the gene-chip method. If the result of the MIC method was set as the golden standard, the sensitivity, specificity, PPV, NPV, and accuracy of PhaB assay were 100%, 95.6%, 91.4%, 100%, and 97.0% respectively. The sensitivity, specificity, PPV, NPV, and accuracy were 98.1%, 96.5%, 92.9%, 99.1%, and 97.0% for the Bactec-960 system, and they were 88.7%, 96.5%, 92.2%, 94.8%, and 94.0% respectively for the gene-chip method. CONCLUSIONS: The PhaB assay is highly sensitive and specific, and its result is highly consistent with those of the Bactec-960 system and the MIC method. It is easy to use and took only three days in the detection of drug susceptibility of INH in clinical isolates of MTB. The results indicate that this low-cost assay can be used in rapid screening for INH resistance in MTB isolates. The MIC method proves to be as efficient as the Bactec-960 system, but whether it can be used as the standard method still needs further investigation. The sensitivity of the gene-chip method is lower as compared to the other methods, and therefore can only be used as an ancillary test.

[Reactive nitrogen loss pathways and their effective factors in paddy field in southern China].

Based on the literature data, the N20 emission, N leaching, N runoff and NH3 volatilization were compared from different rice production regions and their effective factors were evaluated. The results showed that N2 0 emission, N leaching and N runoff in single rice in Yangtze River basin were higher than in other rice production regions, with N loss of 1.89, 6.4 and 10.4 kg N · hm(-2), and N loss rate of 0.8%, 3.8% and 5.3%, respectively. The high N20 emission, N leaching and N runoff in these regions might be attributed to high-rate N application and dry-wet alternation. The NH3 volatilization was the highest in late rice in southern China, with N loss of 54.9 kg N · hm(-2) and N loss rate of 35.2% due to higher temperature at late rice growing stage. In the field, the practice often decreased one reactive N loss but increased another one, indicating that intergated practical management is necessary to reduce reactive N loss. Reactive N loss often increase with increasing grian yield, which is associed with the high-rate N application. The N20 emission, N leaching and N runoff decreased with increasing the partial factor productivity of applied N (PFP). Therefore, reducing N losses per unit of yield is necessary for integrating higher yield with minimum environmental pollution.

[The use of gene chip in detecting Mycobacterium tuberculosis resistant to rifampin and isoniazid].

OBJECTIVE: To study the application of gene chip in detecting Mycobacterium tuberculosis resistant to rifampin (RFP) and isoniazid (INH). METHODS: Probes were designed and the gene chip was fabricated according to the 30 single nucleotide polymorphisms of 11 mutations on 4 genes associated with RFP and INH resistance. The mutations in Mycobacterium tuberculosis were detected by gene chip to analyze the resistance to INH and RFP. RESULTS: 85 of 110 (77.3%) strains resistant to INH and 22 of 30 (73.3%) strains sensitive to INH were detected, while 77 of 94 (81.9%) strains resistant to RFP and 40 of 46 (87.0%) strains sensitive to RFP were detected. The results from the gene-chip detection were consistent with the sequence information. CONCLUSION: The gene-chip technology, a fast test with high accuracy, specificity and sensitivity, as shown in our study, is promising in the clinical detection of Mycobacterium tuberculosis resistant to INH and RFP.

[Application of rapid detection for rifampin resistance in clinical isolates of Mycobacterium tuberculosis by phage amplified biologically assay].

OBJECTIVE: To set up a rapid detection method for rifampin susceptibility with phage amplified biologically (PhaB) assay and to evaluates its value in the detection of rifampin resistance in clinical isolates of Mycobacterium tuberculosis. METHODS: The assay was established to detect rifampin resistance in 524 clinical isolates of Mycobacterium tuberculosis, and the result was compared to that of the absolute concentration method. The minimum inhibitory concentration (MIC) was detected by BACTEC MGIT 960 method for the discrepant isolates. RESULTS: Rifampin susceptibility results were available for 524 strains of Mycobacterium tuberculosis. A total of 223 strains were found to be rifampin resistant and 301 strains were rifampin susceptible detected by PhaB assay, but 211 and 313 strains were respectively found to be rifampin resistant and susceptible by conventional methods. There were 198 and 288 rifampin resistant and susceptible strains both detected by the two methods. The drug susceptibility of 35 strains was the same in 38 discrepant isolates by the PhaB assay and absolute concentration method. The sensitivity, specificity, positive and negative predictive values as well as the overall accuracy for the PhaB assay was 93.8%, 92.0%, 88.8%, 95.7% and 92.7% respectively if the judgment standard was adopted by conventional methods. CONCLUSION: The result of PhaB assay was available within 2 days. This method, which is simple and does not need special equipment, can be used for rapid screening for rifampin resistance from Mycobacterium tuberculosis.