Effluents from hospital and aquaculture are considered important sources of quinolone resistance. However, little information is available on the impact of this effluent on nearby rivers. In this study, 188 ciprofloxacin-resistant bacterial isolates obtained from rivers near hospitals and aquaculture were screened for plasmid-mediated quinolone resistance (PMQR) genes. Species identification, antibiotic susceptibility testing, and PMQR gene transferability assessment were conducted for PMQR-positive bacteria. Representative qnrS2-encoding plasmids were subsequently sequenced using a primer-walking approach. In total, 44 isolates (23.4%) were positive for qnr genes (16 qnrB2, 3 qnrS1, and 25 qnrS2) and 32 isolates (17.0%) were positive for aac(6′)-Ib-cr. Other PMQR genes were not detected. The qnrB2 and aac(6′)-Ib-cr genes had a higher prevalence in aquaculture samples than in hospital samples, and were significantly associated with Enterobacteriaceae (p < 0.05). In contrast, the prevalence of qnrS2 was not site-related, but was significantly associated with Aeromonas spp. (p < 0.05). All PMQR isolates were resistant to three or more classes of antibiotics. Eleven qnrS2-harboring plasmids from Aeromonas spp., including a novel conjugative plasmid pHP18, were selected for sequencing. These plasmids were small in size (6,388–16,197 bp) and belonged to the IncQ or IncU plasmid family, with qnrS2 being part of a mobile insertion cassette. Taken together, our findings suggest that aquaculture is a possible source for aac(6′)-Ib-cr and qnrB2 dissemination, and demonstrate the ubiquity of qnrS2 in aquatic environments. Finally, Aeromonas spp. served as vectors for qnrS2 with the help of IncQ-type plasmids.

Few studies have focused explicitly on the later stages of the fragmentation process, or “late-stage fragmentation”, during which habitat area and patch number decrease simultaneously. This lack of attention is despite the fact that many of the anthropogenically fragmented habitats around the world are, or soon will be, in late-stage fragmentation. Understanding the ecological processes and patterns that occur in late-stage fragmentation is critical to protect the species richness in these fragments. We investigated plant species composition on 152 islands in the Thousand Island Lake, China. A random sampling method was used to create simulated fragmented landscapes with different total habitat areas and numbers of patches mimicking the process of late-stage fragmentation. The response of the landscape-scale species-area relationship (LSAR) to fragmentation per se was investigated, and the contribution of inter-specific differences in the responses to late-stage fragmentation was tested. We found that the loss of species at small areas was compensated for by the effects of fragmentation per se, i.e., there were weak area effects on species richness in landscapes due to many patches with irregular shapes and high variation in size. The study also illustrated the importance of inter-specific differences for responses to fragmentation in that the LSARs of rare and common species were differently influenced by the effects of fragmentation per se. In conclusion, our analyses at the landscape scale demonstrate the significant influences of fragmentation per se on area effects and the importance of inter-specific differences for responses to fragmentation in late-stage fragmentation. These findings add to our understanding of the effects of habitat fragmentation on species diversity.