Quantitative competitive PCR as a technique for exploring flea-Yersina pestis dynamics.

Engelthaler, David M.; Hinnebusch, B. Joseph; Rittner, C M; Gage, Kenneth L.

doi:10.4269/ajtmh.2000.62.552

Cited by 66 publications

(100 citation statements)

References 28 publications

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“…Such high bacterial concentrations (> 10 6 cfu/mL) are needed to reliably infect feeding fleas. 35,36 Death of the host forces infected fleas to seek new hosts of the same or different species. As a consequence of this relay of transmission from infectious host to vector to mobile susceptible host, Y. pestis can move rapidly across a landscape.…”

Section: Discussionmentioning

confidence: 99%

Flea Diversity and Infestation Prevalence on Rodents in a Plague-Endemic Region of Uganda

Amatre¹,

Babi²,

Enscore³

et al. 2009

The American Journal of Tropical Medicine and Hygiene

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Abstract. In Uganda, the West Nile region is the primary epidemiologic focus for plague. The aims of this study were to 1) describe flea-host associations within a plague-endemic region of Uganda, 2) compare flea loads between villages with or without a history of reported human plague cases and between sampling periods, and 3) determine vector loads on small mammal hosts in domestic, peridomestic, and sylvatic settings. We report that the roof rat, Rattus rattus , is the most common rodent collected in human dwellings in each of the 10 villages within the two districts sampled. These rats were commonly infested with efficient Y. pestis vectors, Xenopsylla cheopis and X. brasiliensis in Arua and Nebbi districts, respectively. In peridomestic and sylvatic areas in both districts, the Nile rat, Arvicanthus niloticus , was the most abundant rodent and hosted the highest diversity of flea species. When significant temporal differences in flea loads were detected, they were typically lower during the dry month of January. We did not detect any significant differences in small mammal abundance or flea loads between villages with our without a history of human plague, indicating that conditions during inter-epizootic periods are similar between these areas. Future studies are needed to determine whether flea abundance or species composition changes during epizootics when humans are most at risk of exposure.

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Section: Discussionmentioning

confidence: 99%

Flea Diversity and Infestation Prevalence on Rodents in a Plague-Endemic Region of Uganda

Amatre¹,

Babi²,

Enscore³

et al. 2009

The American Journal of Tropical Medicine and Hygiene

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“…Y. pestis does not adhere to or invade the midgut epithelium, putting it at risk of being eliminated in the feces because fleas feed and defecate frequently. In fact, up to half of X. cheopis rapidly clear themselves of infection in this way even after feeding on blood containing more than 10 8 Y. pestis per milliliter (Engelthaler et al 2000;Lorange et al 2005;Pollitzer 1954). Thus, the formation of multicellular aggregates that are too large to pass in the feces may be important to produce a stable infection.…”

Section: Characteristics Of the Y Pestis Transmissible Biofilm Produmentioning

confidence: 99%

Yersinia pestis Biofilm in the Flea Vector and Its Role in the Transmission of Plague

Hinnebusch¹,

Erickson²

2008

Current Topics in Microbiology and Immunology

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Transmission by fleabite is a relatively recent evolutionary adaptation of Yersinia pestis, the bacterial agent of bubonic plague. To produce a transmissible infection, Y. pestis grows as an attached biofilm in the foregut of the flea vector. Biofilm formation both in the flea foregut and in vitro is dependent on an extracellular matrix (ECM) synthesized by the Yersinia hms gene products. The hms genes are similar to the pga and ica genes of Escherichia coli and Staphylococcus epidermidis, respectively, that act to synthesize a poly-β-1,6-N-acetyl-dglucosamine ECM required for biofilm formation. As with extracellular polysaccharide production in many other bacteria, synthesis of the Hms-dependent ECM is controlled by intracellular levels of cyclic-di-GMP. Yersinia pseudotuberculosis, the food-and water-borne enteric pathogen from which Y. pestis evolved recently, possesses identical hms genes and can form biofilm in vitro but not in the flea. The genetic changes in Y. pestis that resulted in adapting biofilm-forming capability to the flea gut environment, a critical step in the evolution of vector-borne transmission, have yet to be identified. During a flea bite, Y. pestis is regurgitated into the dermis in a unique biofilm phenotype, and this has implications for the initial interaction with the mammalian innate immune response.

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“…The ability to form biofilm blockage may be limited by infectious dose (10,20) or defective acquisition of the pathogen; fleas infected with the ⌬hfq mutant showed lower infectious doses (Յ50% wild-type CFU/flea at T ϭ 0) immediately following feeding compared to the wild type (Fig. 3A).…”

Section: Fig 1 Growth Fitness Comparison Of Y Pestismentioning

confidence: 99%

Hfq Regulates Biofilm Gut Blockage That Facilitates Flea-Borne Transmission of Yersinia pestis

2012

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The plague bacillus Yersinia pestis can achieve transmission by biofilm blockage of the foregut proventriculus of its flea vector. Hfq is revealed to be essential for biofilm blockage formation and acquisition and fitness of Y. pestis during flea gut infection, consistent with posttranscriptional regulatory mechanisms in plague transmission.Y ersinia pestis, the etiological agent of bubonic plague, is transmitted to humans by fleabite. Colonization and biofilm formation by Y. pestis in the flea gut are essential steps for proventricular foregut blockage and facilitate subsequent transmission of Y. pestis during "frustrated feeding" by an infected flea (16,20). The known transmission factors hmsHFRS, gmhA, and ymt are required for flea-borne transmission but are dispensable for infection within the mammalian host (8,(16)(17)(18)(19). Whole-genome comparative transcriptional profiling revealed, however, that these three genes are not differentially transcribed during Y. pestis biofilm formation and gut blockage of the flea relative to temperature-matched in vitro conditions (40). Clearly, the transcriptome provides only a first order of gene regulation, while a second order of posttranscriptional regulation may shape the unique flea-associated biofilm that allows transmission. This is in keeping with the emerging paradigm for extensive posttranscriptionally regulated virulence in numerous bacterial pathogens (6,25,29,(32)(33)(34) The hfq gene is abundantly transcribed during Y. pestis biofilm proventricular blockage (40), predicting a second order of posttranscriptional regulation directed by Hfq during Y. pestis flea infection. To investigate the role of Hfq in mediating flea gut blockage, an hfq deletion mutant in the Y. pestis KIM6ϩ strain was constructed using the lambda red recombinase system (9). This strain contains the hmsHFRS gene locus required for the synthesis of extracellular matrix polysaccharide (EPS) essential for biofilm formation and flea foregut blockage (18,31,39). We hypothesized that the ⌬hfq mutant growing in vitro at the 21°C insect host temperature or within the flea gut would be impaired in its growth and biofilm gut blockage capability essential for plague survival and transmission.Growth of a Y. pestis KIM6؉ hfq deletion mutant. Functional mutations of hfq frequently result in compromised bacterial growth fitness (6, 13), including in Y. pestis growing at the mammalian host temperature of 37°C versus laboratory growth at 28°C (3, 13). Here, at 21°C, the insect host temperature, the ⌬hfq mutant, relative to its isogenic wild type, exhibited a significantly impaired specific growth rate and a decrease in stationary-phase cell density (Fig. 1A) similar to those seen with growth at 37°C (3, 13) and at 28°C (Fig. 1B) in brain heart infusion broth (BHI). The ⌬hfq mutant, complemented with the native gene and promoter region of hfq on a high-copy-number plasmid, pCR4-TOPO (Invitrogen), sufficiently rescued this growth fitness defect in BHI broth. However, the ⌬hfq mutant showed no significant...

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Quantitative competitive PCR as a technique for exploring flea-Yersina pestis dynamics.

Cited by 66 publications

References 28 publications

Flea Diversity and Infestation Prevalence on Rodents in a Plague-Endemic Region of Uganda

Flea Diversity and Infestation Prevalence on Rodents in a Plague-Endemic Region of Uganda

Yersinia pestis Biofilm in the Flea Vector and Its Role in the Transmission of Plague

Hfq Regulates Biofilm Gut Blockage That Facilitates Flea-Borne Transmission of Yersinia pestis

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