Research Article: Detection of Rickettsia spp in Ticks by MALDI-TOF MS

Date Published: February 6, 2015

Publisher: Public Library of Science

Author(s): Amina Yssouf, Lionel Almeras, Jérôme Terras, Cristina Socolovschi, Didier Raoult, Philippe Parola, David H Walker.

Abstract: BackgroundMatrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) has been shown to be an effective tool for the rapid identification of arthropods, including tick vectors of human diseases.Methodology/Principal FindingsThe objective of the present study was to evaluate the use of MALDI-TOF MS to identify tick species, and to determine the presence of rickettsia pathogens in the infected Ticks. Rhipicephalus sanguineus and Dermacentor marginatus Ticks infected or not by R. conorii conorii or R. slovaca, respectively, were used as experimental models. The MS profiles generated from protein extracts prepared from tick legs exhibited mass peaks that distinguished the infected and uninfected Ticks, and successfully discriminated the Rickettsia spp. A blind test was performed using Ticks that were laboratory-reared, collected in the field or removed from patients and infected or not by Rickettsia spp. A query against our in-lab arthropod MS reference database revealed that the species and infection status of all Ticks were correctly identified at the species and infection status levels.Conclusions/SignificanceTaken together, the present work demonstrates the utility of MALDI-TOF MS for a dual identification of tick species and intracellular bacteria. Therefore, MALDI-TOF MS is a relevant tool for the accurate detection of Rickettsia spp in Ticks for both field monitoring and entomological diagnosis. The present work offers new perspectives for the monitoring of other vector borne diseases that present public health concerns.

Partial Text: Ticks are obligate hematophagous arthropods that parasitize vertebrates in almost all regions of the world and are currently considered to be the second-most important vectors of human infectious diseases worldwide, after mosquitoes [1]. Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia. These zoonoses are among the oldest known vector-borne diseases, and include Mediterranean spotted fever, which is caused by Rickettsia conorii conorii and transmitted by the brown dog tick Rhipicephalus sanguineus. Additionally they include most of the emerging tick-borne diseases such as the infection caused by R. slovaca which is transmitted by Dermacentor spp [1, 2].

After the demonstration that MALDI-TOF MS profiling is an accurate tool to identify arthropods [19–23], including vectors of infectious diseases such as Ticks [4, 24], the possibility of identifying the presence of microorganisms inside the vectors became evident.



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