Dataset Information

Cultivation of Rickettsia amblyommii in tick cells, prevalence in Florida lone star ticks (Amblyomma americanum).

ABSTRACT: BACKGROUND: Rickettsia amblyommii is a bacterium in the spotted fever group of organisms associated with the lone star tick (LST), Amblyomma americanum. The LST is the most commonly reported tick to parasitize humans in the southeastern US. Within this geographic region, there have been suspected cases of Rocky Mountain spotted fever (RMSF) where the causative agent, R. rickettsii, was not identified in the local tick population. In these areas, patients with clinical signs of RMSF had low or no detectable antibodies to R. rickettsii, resulting in an inability to confirm a diagnosis. METHODS: R. amblyommii was cultivated from host-seeking LSTs trapped in Central Florida and propagated in ISE6 (Ixodes scapularis) and AAE2 (A. americanum) cells. Quantitative PCR targeting the 17-kD gene of Rickettsia spp. identified the genus of the organism in culture. Variable regions of groEL, gtlA and rompA genes were amplified and sequenced to confirm the species. The prevalence of R. amblyommii in LSTs within the geographic region was determined by qPCR followed by conventional PCR and direct sequencing. RESULTS: Analyses of amplified sequences from the cultured organism were 100% homologous to R. amblyommii. The overall prevalence of Rickettsia spp. in the local population of LSTs was 57.1% and rompA sequence analysis identified only R. amblyommii in LSTs. CONCLUSIONS: A Florida strain of R. amblyommii was successfully cultivated in two tick cell lines. Further evaluation of the new strain and comparisons to the other geographic strains is needed. The prevalence of this SFG organism in the tick population warrants further investigation into the organism's ability to cause clinical disease in mammalian species.

SUBMITTER: Sayler KA

PROVIDER: S-EPMC4077227 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Cultivation of Rickettsia amblyommii in tick cells, prevalence in Florida lone star ticks (Amblyomma americanum).

Sayler Katherine A KA Wamsley Heather L HL Pate Melanie M Barbet Anthony F AF Alleman A Rick AR

Parasites & vectors 20140613

<h4>Background</h4>Rickettsia amblyommii is a bacterium in the spotted fever group of organisms associated with the lone star tick (LST), Amblyomma americanum. The LST is the most commonly reported tick to parasitize humans in the southeastern US. Within this geographic region, there have been suspected cases of Rocky Mountain spotted fever (RMSF) where the causative agent, R. rickettsii, was not identified in the local tick population. In these areas, patients with clinical signs of RMSF had lo ...[more]

PMID: 24927809

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Project description:The Lone Star tick, Amblyomma americanum, transmits several bacterial pathogens including species of Anaplasma and Ehrlichia. Amblyomma americanum also hosts a number of non-pathogenic bacterial endosymbionts. Recent studies of other arthropod and insect vectors have documented that commensal microflora can influence transmission of vector-borne pathogens; however, little is known about tick microbiomes and their possible influence on tick-borne diseases. Our objective was to compare bacterial communities associated with A. americanum, comparing Anaplasma/Ehrlichia -infected and uninfected ticks. Field-collected questing specimens (n = 50) were used in the analyses, of which 17 were identified as Anaplasma/Ehrlichia infected based on PCR amplification and sequencing of groEL genes. Bacterial communities from each specimen were characterized using Illumina sequencing of 16S rRNA gene amplicon libraries. There was a broad range in diversity between samples, with inverse Simpson's Diversity indices ranging from 1.28-89.5. There were no statistical differences in the overall microbial community structure between PCR diagnosed Anaplasma/Ehrlichia-positive and negative ticks, but there were differences based on collection method (P < 0.05), collection site (P < 0.05), and sex (P < 0.1) suggesting that environmental factors may structure A. americanum microbiomes. Interestingly, there was not always agreement between Illumina sequencing and PCR diagnostics: Ehrlichia was identified in 16S rRNA gene libraries from three PCR-negative specimens; conversely, Ehrlichia was not found in libraries of six PCR-positive ticks. Illumina sequencing also helped identify co-infections, for example, one specimen had both Ehrlichia and Anaplasma. Other taxa of interest in these specimens included Coxiella, Borrelia, and Rickettsia. Identification of bacterial community differences between specimens of a single tick species from a single geographical site indicates that intra-species differences in microbiomes were not due solely to pathogen presence/absence, but may be also driven by vector life history factors, including environment, life stage, population structure, and host choice.

Dataset Information

Cultivation of Rickettsia amblyommii in tick cells, prevalence in Florida lone star ticks (Amblyomma americanum).

Publications

Cultivation of Rickettsia amblyommii in tick cells, prevalence in Florida lone star ticks (Amblyomma americanum).

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