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Evaluation of a liquid carbaryl formulation to control burrow fleas following a die-off of black-tailed prairie dogs ( Cynomys ludovicianus) caused by plague ( Yersinia pestis) in Converse County, Wyoming

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Russell E Enscore  1 , Ying Bai  2 , Lynn M Osikowicz  2 , Christopher Sexton  2 , Daniel R O’Leary  3   4
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References

    1. 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.
    1. Barnes, A.M., L.J. Ogden, and E.G. Campos. 1972. Control of the plague vector, <italic>Opisocrostis</italic> hirsutus, by treatment of prairie dog (<italic>Cynomys ludovicianus</italic>) burrows with 2% carbaryl dust. J. Med. Entomol. 9: 330–333.
    1. Barnes, A.M. 1982. Surveillance and control of bubonic plague in the United States. Symp. Zool. Soc. Lond. 50: 237–270.
    1. Biggins, D.E., J.L. Godbey, K.L. Gage, L.G. Carter, and J.A. Montenieri. 2010. Vector control improves survival of three species of prairie dogs (<italic>Cynomys</italic>) in areas considered enzootic for plague. Vector-Borne Zoonotic Dis. 10: 17–26.
    1. Chu, M.C. 2000. <italic>Laboratory Manual of Plague Diagnostic Tests</italic>. Centers for Disease Control and Prevention, Fort Collins, CO, and World Health Organization, Geneva. 129 pp.
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A novel mechanism of streptomycin resistance in Yersinia pestis: Mutation in the rpsL gene

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Abstract

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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Pentaplex real-time PCR for differential detection of Yersinia pestis and Y. pseudotuberculosis and application for testing fleas collected during plague epizootics

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Microbiologyopen. 2020 Oct;9(10):e1105. doi: 10.1002/mbo3.1105. Epub 2020 Aug 12.

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Abstract

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.
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