Miarinjara A(1)(2), Eads DA(3), Bland DM(1), Matchett MR(4), Biggins DE(3), Hinnebusch BJ(1). Author information: (1)Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, MT, USA. (2)Department of Environmental Sciences, Emory University, Atlanta, GA, USA. (3)U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO, USA. (4)U.S. Fish and Wildlife Service, Lewistown, MT, USA. Prairie dogs in the western United States experience periodic epizootics of plague, caused by the flea-borne bacterial pathogen Yersinia pestis. An early study indicated that Oropsylla hirsuta (Baker), often the most abundant prairie dog flea vector of plague, seldom transmits Y. pestis by the classic blocked flea mechanism. More recently, an alternative early-phase mode of transmission has been proposed as the driving force behind prairie dog epizootics. In this study, using the same flea infection protocol used previously to evaluate early-phase transmission, we assessed the vector competence of O. hirsuta for both modes of transmission. Proventricular blockage was evident during the first two weeks after infection and transmission during this time was at least as efficient as early-phase transmission 2 d after infection. Thus, both modes of transmission likely contribute to plague epizootics in prairie dogs. Published by Oxford University Press on behalf of Entomological Society of America 2022. DOI: 10.1093/jme/tjac021 PMID: 35380675
- Bai, Y., V. Motin, R.E. Enscore, L. Osikowicz, M.R. Rizzo, A. Hojgaard, M. Kosoy, and R.J. Eisen. 2020. Pentaplex real-time PCR for differential detection of <italic>Yersinia pestis</italic> and Y. pseudotuberculosis and application for testing fleas collected during plague epizootics. MicrobiologyOpen, 11 pp., doi: 10.1002/mbo3.1105.
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The annual meeting of Prairie Dog Pals was conducted on 6 February 2022. The link to the meeting minutes follows: Meeting Minutes:
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 strep- tomycin 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 resis- tance 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 sequenc- ing 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 strep- tomycin 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.
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Microbiologyopen. 2020 Oct;9(10):e1105. doi: 10.1002/mbo3.1105. Epub 2020 Aug 12.
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Upon acquiring two unique plasmids (pMT1 and pPCP1) and genome rearrangement during the evolution from Yersinia pseudotuberculosis, the plague causative agent Y. pestis is closely related to Y. pseudotuberculosis genetically but became highly virulent. We developed a pentaplex real-time PCR assay that not only detects both Yersinia species but also differentiates Y. pestis strains regarding their plasmid profiles. The five targets used were Y. pestis-specific ypo2088, caf1, and pst located on the chromosome, plasmids pMT1 and pPCP1, respectively; Y. pseudotuberculosis-specific chromosomal gene opgG; and 18S ribosomal RNA gene as an internal control for flea DNA. All targets showed 100% specificity and high sensitivity with limits of detection ranging from 1 fg to 100 fg, with Y. pestis-specific pst as the most sensitive target. Using the assay, Y. pestis strains were differentiated 100% by their known plasmid profiles. Testing Y. pestis and Y. pseudotuberculosis-spiked flea DNA showed there is no interference from flea DNA on the amplification of targeted genes. Finally, we applied the assay for testing 102 fleas collected from prairie dog burrows where prairie dog die-off was reported months before flea collection. All flea DNA was amplified by 18S rRNA; no Y. pseudotuberculosis was detected; one flea was positive for all Y. pestis-specific targets, confirming local Y. pestis transmission. Our results indicated the assay is sensitive and specific for the detection and differentiation of Y. pestis and Y. pseudotuberculosis. The assay can be used in field investigations for the rapid identification of the plague causative agent.