[Simulation of Needle Reflectance Spectrum and Sensitivity Analysis of Biochemical Parameters of Pinus Yunnanensis in Different Healthy Status].

The sensitivity of biochemical effects on leaf reflectance is vital for retieving biochemical parameters with remote sensing. In this study, the chlorophyll and water absorption coefficients of the commonly used model LIBERTY (leaf incorporation biochemistry exhibiting reflectance and transmittance yields) were calibrated using field measured needle spectral reflectance curves based on a look up table (LUT) method. A novel spectra reflectance fitting method were presented by involving a new index (named as yellow index, YI), which could obviously improve the fitting accuracy of Pinus yunnanensis reflection spectrum at highly-stressed status. As a global sensitivity analysis method, the EFAST (extended Fourier amplitued sensitivity test) was implemented to quantitatively assess the sensitivity of biochemical parameters on needle reflectance. Results show that: (1) the reflectauce spectrum of healthy needles (R2=0.999，RMSE＜0.01), slightly stressed needles (R2=0.991, RMSE＜0.02) and moderately stressed needles (R2=0.992，RMSE＜0.03) are simulated fairly well by calibrated LIBERTY model which has less potential in fitting the reflectance spectrum of seriously stressed needles (R2=0.803，RMSE＞0.1). (2) the reflectance spectrum of seriously stressed needles can be successfully simulated by our proposed spectrum reflectance fitting method (R2=0.991, RMSE<0.03), because YI can quantitatively describe different degrees of stress, and (3) the sensitivity of leaf reflectance to chlorophyll and water parameters decreases with the degree of stress; while the sensitivity to other biochemical parameters is increasing, which includ baseline absorption, albino absorption, Lignin and Cellulose content, and nitrogen content, increases with the stress degree. Needle reflectance spectrum also have sensitivive bands for these parameters. For example, the albino absorption have a significant effect on needle reflectance in 505～565 and 705～850 nm). In addition, Albino absorption and chlorophyll also have significant effects on needle reflectance in visible region for seriously stressed needles, which indicates that the prior knowledge of the albino absorption level can help obtain the valid inversion result of chlorophyll content.

Fitness Advantage of mcr-1-Bearing IncI2 and IncX4 Plasmids in Vitro.

The objective of this study was to assess the impact of diverse plasmids bearing colistin resistance gene mcr-1 on host fitness. Forty-seven commensal E. coli isolates recovered from the pig farm where mcr-1 was first identified were screened for mcr-1. mcr-1-bearing plasmids were characterized by sequencing. The fitness impact of mcr-1-bearing plasmids was evaluated by in vitro competition assays. Twenty-seven (57.5%) E. coli isolates were positive for mcr-1. The mcr-1 genes were mainly located on plasmids belonging to IncI2 (n = 5), IncX4 (n = 11), IncHI2/ST3 (n = 8), IncFII (n = 2), and IncY (n = 2). InHI2 plasmids also carried other resistance genes (floR, blaCTX-M, and fosA3) and were only detected in isolates from nursery pigs. Sequences of the representative mcr-1-bearing plasmids were almost identical to those of the corresponding plasmid types reported previously. An increase in the fitness of IncI2- and IncX4-carrying strains was observed, while the presence of IncHI2, IncFII and IncY plasmids showed a fitness cost although an insignificant fitness increase was initially observed in IncFII or IncY plasmids-containing strains. Acquisition of IncI2-type plasmid was more beneficial for host E. coli DH5α than either IncHI2 or IncX4 plasmid, while transformants with IncHI2-type plasmid presented a competitive disadvantage against IncI2 or IncX4 plasmid containing strains. In conclusion, IncI2, IncX4, and IncHI2 were the major plasmid types driving the dissemination of mcr-1 in this farm. Increased fitness or co-selection by other antimicrobials might contribute to the further dissemination of the three epidemic mcr-1-positive plasmids (IncI2, IncX4, and IncHI2) in this farm and worldwide.

Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study.

BACKGROUND: Until now, polymyxin resistance has involved chromosomal mutations but has never been reported via horizontal gene transfer. During a routine surveillance project on antimicrobial resistance in commensal Escherichia coli from food animals in China, a major increase of colistin resistance was observed. When an E coli strain, SHP45, possessing colistin resistance that could be transferred to another strain, was isolated from a pig, we conducted further analysis of possible plasmid-mediated polymyxin resistance. Herein, we report the emergence of the first plasmid-mediated polymyxin resistance mechanism, MCR-1, in Enterobacteriaceae. METHODS: The mcr-1 gene in E coli strain SHP45 was identified by whole plasmid sequencing and subcloning. MCR-1 mechanistic studies were done with sequence comparisons, homology modelling, and electrospray ionisation mass spectrometry. The prevalence of mcr-1 was investigated in E coli and Klebsiella pneumoniae strains collected from five provinces between April, 2011, and November, 2014. The ability of MCR-1 to confer polymyxin resistance in vivo was examined in a murine thigh model. FINDINGS: Polymyxin resistance was shown to be singularly due to the plasmid-mediated mcr-1 gene. The plasmid carrying mcr-1 was mobilised to an E coli recipient at a frequency of 10(-1) to 10(-3) cells per recipient cell by conjugation, and maintained in K pneumoniae and Pseudomonas aeruginosa. In an in-vivo model, production of MCR-1 negated the efficacy of colistin. MCR-1 is a member of the phosphoethanolamine transferase enzyme family, with expression in E coli resulting in the addition of phosphoethanolamine to lipid A. We observed mcr-1 carriage in E coli isolates collected from 78 (15%) of 523 samples of raw meat and 166 (21%) of 804 animals during 2011-14, and 16 (1%) of 1322 samples from inpatients with infection. INTERPRETATION: The emergence of MCR-1 heralds the breach of the last group of antibiotics, polymyxins, by plasmid-mediated resistance. Although currently confined to China, MCR-1 is likely to emulate other global resistance mechanisms such as NDM-1. Our findings emphasise the urgent need for coordinated global action in the fight against pan-drug-resistant Gram-negative bacteria. FUNDING: Ministry of Science and Technology of China, National Natural Science Foundation of China.