Urban-ecological landscape connectivity and pattern optimization can significantly enhance biodiversity and sustainable development capacity, which play an important role in continued ecosystem functioning. Previous studies identified ecological sources based on the area threshold method or combination with morphological spatial pattern analysis and the landscape connectivity index (CMSPACI) method, but few studies have compared the advantages, disadvantages, and applicability of the two methods. In this paper, taking Nanchang as the study area, we address the ecological sources via area threshold and the CMSPACI method. Then, the minimum cost distance method is used to generate potential corridors of different methods, and the differences in ecological networks are analyzed. Finally, the circuit theory is used to identify barriers, and we provide targeted recommendations for ecological network pattern optimization in the study area. The results show that (1) the ecological sources extracted by different methods are different. The ecological sources extracted by the area threshold are far away from the surrounding sources, and the landscape connectivity is low. The ecological sources identified by the CMSPACI method are closely related to the surrounding sources, and the landscape connectivity is high. (2) Compared with the area threshold method, the habitat quality of corridors under the CMSPACI method is better, and the interaction intensity between patches is larger. (3) There is little difference in the number of ecological barriers under different methods; all of them are located between patches or on the edge of patches, and most of them are roads or construction land. Overall, the area threshold method is simpler. Ecological sources can be effectively addressed through the CMSPACI method, and the landscape connectivity of the ecological network will be better. This study provides an important reference for the selection of ecological sources in the construction of ecological networks.

Colistin is a last-resort antimicrobial used to treat infections caused by multidrug-resistant Gram-negative bacilli (MDR-GNB). The emergence of colistin resistance, particularly linked to mobile genetic elements including the mcr genes, is a major threat to the management of MDR-GNB infections. The aim of this study was to assess the presence of mcr genes in a collection of 40 colistin-resistant commensal Escherichia coli isolated from healthy pigs, cattle and poultry in Belgium between 2012 and 2016. All isolates carried at least one mcr gene. The genes mcr-1 to -5 were observed in this collection. Different replicons associated with mcr genes were identified, including IncHI2/IncHI2A associated with mcr-1, IncX4 associated with mcr-1 and mcr-2, and ColE10 associated with mcr-4. While the occurrence of multiple mcr genes in a single isolate has rarely been reported elsewhere, a triple occurrence (mcr-1, -3 and -5) was found in this study. All isolates were MDR and carried between one and nine different replicons. Seventeen different sequence types were observed among the 40 E. coli isolates. In conclusion, this study revealed the presence of a reservoir of mobile colistin resistance genes (mcr-1 to -5) observed during at least 5 years (2012-2016) in the commensal gut flora of pigs, cattle and poultry in Belgium.