Various Mobile Genetic Elements Involved in the Dissemination of the Phenicol-Oxazolidinone Resistance Gene optrA in the Zoonotic Pathogen Streptococcus suis: a Nonignorable Risk to Public Health.

The rapid increase of phenicol-oxazolidinone (PhO) resistance in Streptococcus suis due to transferable resistance gene optrA is a matter of concern. However, genetic mechanisms for the dissemination of the optrA gene remain to be discovered. Here, we selected 33 optrA-positive S. suis isolates for whole-genome sequencing and analysis. The IS1216E element was present in 85% of the optrA-carrying contigs despite genetic variation observed in the flanking region. IS1216E-optrA-carrying segments could be inserted into larger mobile genetic elements (MGEs), including integrative and conjugative elements, plasmids, prophages, and antibiotic resistance-associated genomic islands. IS1216E-mediated circularization occurred to form the IS1216E-optrA-carrying translocatable units, suggesting a crucial role of IS1216E in optrA spreading. Three optrA-carrying MGEs (ICESsuAKJ47_SSU1797, plasmid pSH0918, and prophage ΦSsuFJSM5_rum) were successfully transferred via conjugation at different transfer frequencies. Interestingly, two types of transconjugants were observed due to the multilocus integration of ICESsuAKJ47 into an alternative SSU1943 attachment site along with the primary SSU1797 attachment site (type 1) or into the single SSU1797 attachment site (type 2). In addition, conjugative transfer of an optrA-carrying plasmid and prophage in streptococci was validated for the first time. Considering the abundance of MGEs in S. suis and the mobility of IS1216E-optrA-carrying translocatable units, attention should be paid to the potential risks to public health from the emergence and spread of PhO-resistant S. suis. IMPORTANCE Antimicrobial resistance to phenicols and oxazolidinones by the dissemination of the optrA gene leads to treatment failure in both veterinary and human medicine. However, information about the profile of these MGEs (mobilome) that carry optrA and their transferability in streptococci was limited, especially for the zoonotic pathogen S. suis. This study showed that the optrA-carrying mobilome in S. suis includes integrative and conjugative elements (ICEs), plasmids, prophages, and antibiotic resistance-associated genomic islands. IS1216E-mediated formation of optrA-carrying translocatable units played important roles in optrA spreading between types of MGEs, and conjugative transfer of various optrA-carrying MGEs (ICEs, plasmids, and prophages) further facilitated the transfer of optrA across strains, highlighting a nonignorable risk to public health of optrA dissemination to other streptococci and even to bacteria of other genera.

[Dynamic changes of landscape pattern and eco-disturbance degree in Shuangtai estuary wetland of Liaoning Province, China].

The main objective of establishing natural reserve is to protect its natural resources from human disturbances and maintain its critical ecological service values. This paper introduced the concept of hemeroby, and by using remote sensing technology, systematically assessed the dynamic changes of landscape pattern and eco-disturbance degree in Shuangtai estuary wetland of Liaoning Province, China. Firstly, a knowledge-based expert system was used to classify the landscape into three first-level types based on eco-disturbance degree, i.e., undisturbed, partially disturbed, or completely disturbed, which were further classified into 30 second-level categories. Secondly, questionnaire and experts knowledge were adopted to determine the hemeroby index for each landscape type and to formulate a landscape classification system. Finally, the landscape classification maps and hemeroby indices were derived by using the Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper Plus (ETM+) data acquired on 30 April 1987, 7 June 1995, 12 June 2000, and 11 October 2006. The results indicated that from 1987 to 2006, the landscape patches in the study area became more fragmented, being most obvious for reed marsh. Undisturbed landscape type decreased in area, while partially and completely disturbed types were in adverse. The overall characteristics of the spatial distribution of hemeroby index were of most variable in the areas along the river and surrounding the estuary and being the highest in the areas surrounding the city, largely due to the rapid urbanization and the blooming fishery in the study area.

Land desertification monitoring and assessment in Yulin of Northwest China using remote sensing and geographic information systems (GIS).

The objective of this study is to develop techniques for assessing and analysing land desertification in Yulin of Northwest China, as a typical monitoring region through the use of remotely sensed data and geographic information systems (GIS). The methodology included the use of Landsat TM data from 1987, 1996 and 2006, supplemented by aerial photos in 1960, topographic maps, field work and use of other existing data. From this, land cover, the Normalised Difference Vegetation Index (NDVI), farmland, woodland and grassland maps at 1:100,000 were prepared for land desertification monitoring in the area. In the study, all data was entered into a GIS using ILWIS software to perform land desertification monitoring. The results indicate that land desertification in the area has been developing rapidly during the past 40 years. Although land desertification has to some extent been controlled in the area by planting grasses and trees, the issue of land desertification is still serious. The study also demonstrates an example of why the integration of remote sensing with GIS is critical for the monitoring of environmental changes in arid and semi-arid regions, e.g. in land desertification monitoring in the Yulin pilot area. However, land desertification monitoring using remote sensing and GIS still needs to be continued and also refined for the purpose of long-term monitoring and the management of fragile ecosystems in the area.