Streptomycin is considered to be one of the effective antibiotics for the treatment of plague. In order to investigate the streptomycin resistance of Y. pestis in China, we evaluated streptomycin susceptibility of 536 Y. pestis strains in China in vitro using the minimal inhibitory concentration (MIC) and screened streptomycin resistance-associated genes (strA and strB) by PCR method. A clinical Y. pestis isolate (S19960127) exhibited high-level resistance to streptomycin (the MIC was 4,096 mg/L). The strain (biovar antiqua) was isolated from a pneumonic plague outbreak in 1996 in Tibet Autonomous Region, China, belonging to the Marmota himalayana Qinghai–Tibet Plateau plague focus. In contrast to previously reported streptomycin resistance mediated by conjugative plasmids, the genome sequencing and allelic replacement experiments demonstrated that an rpsL gene (ribosomal protein S12) mutation with substitution of amino-acid 43 (K43R) was responsible for the high-level resistance to streptomycin in strain S19960127, which is consistent with the mutation reported in some streptomycin-resistant Mycobacterium tuberculosis strains. Streptomycin is used as the first-line treatment against plague in many countries. The emergence of streptomycin resistance in Y. pestis represents a critical public health problem. So streptomycin susceptibility monitoring of Y. pestis isolates should not only include plasmid-mediated resistance but also include the ribosomal protein S12 gene (rpsL) mutation, especially when treatment failure is suspected due to antibiotic resistance.
To provide guidance for plague surveillance and a reliable basis for plague prevention and control, we analyzed the habitat characteristics of Himalayan marmots, developed Himalayan marmot information collection system V3.0 based on global navigation satellite system (GNSS), remote sensing, and geographic information system (“3S”) technology, and drew a predictive spatial distribution map of Himalayan marmots in Qinghai Province. Field survey data of 352 marmot plague sites in Qinghai Province were collected in 2014, and the data from 80 sample sites were included. The Himalayan marmot habitat characteristics were analyzed based on “3S” technology using five environment variables (elevation, slope, aspect, vegetation cover, and grass type) and the geographical coordinates. Himalayan marmot information collection system V3.0, which has been approved by the National Copyright Administration of the People’s Republic of China (No.00764743), was used to draw a predictive spatial distribution map of Himalayan marmots in Qinghai province. Moreover, from 2015 to 2017, positioning data of the plague-foci and plague-free areas in Qinghai Province were collected using GNSS receptor for field validations to verify the accuracy of the marmot predictive spatial distribution map. Elevation, slope, vegetation cover, and grassland type were identified as important environmental factors that determine the spatial distribution of Himalayan marmots. The suitable range of environmental features was 3400–4600 m elevation, 5°–20° slope, 0.60–1.00 vegetation cover, and alpine meadows. The Himalayan marmot predictive spatial distribution map in Qinghai Province based on “3S” technology and marmot information collection system V3.0 had a spatial resolution of 30 m. Field validation in areas of Qinghai Province revealed a prediction accuracy and mean absolute error of 0.8669 and 0.1331, respectively, which indicated excellent prediction accuracy. This study greatly improved the work efficiency of plague surveillance and effectively reduced the work intensity of researchers. Application of “3S” technology and marmot information collection system V3.0 has improved the data collection efficiency, provided new technical means for plague investigation and research, and provided a reference for development of plague surveillance programs. The research results will play a positive role in promoting the improvement and perfection of plague prevention and control strategies in Qinghai province and even in China.
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