Abstract
BackgroundIn Africa, relapsing fever borreliae are neglected vector-borne pathogens that cause mild to deadly septicemia and miscarriage. Screening vectors for the presence of borreliae currently requires technically demanding, time- and resource-consuming molecular methods. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has recently emerged as a tool for the rapid identification of vectors and the identification of cultured borreliae. We investigated whether MALDI-TOF-MS could detect relapsing fever borreliae directly in ticks.Methodology/Principal FindingsAs a first step, a Borrelia MALDI-TOF-MS database was created to house the newly determined Mean Spectrum Projections for four Lyme disease group and ten relapsing fever group reference borreliae. MALDI-TOF-MS yielded a unique protein profile for each of the 14 tested Borrelia species, with 100% reproducibility over 12 repeats. In a second proof-of-concept step, the Borrelia database and a custom software program that subtracts the uninfected O. sonrai profile were used to detect Borrelia crocidurae in 20 Ornithodoros sonrai ticks, including eight ticks that tested positive for B. crocidurae by PCR-sequencing. A B. crocidurae-specific pattern consisting of 3405, 5071, 5898, 7041, 8580 and 9757-m/z peaks was found in all B. crocidurae-infected ticks and not found in any of the un-infected ticks. In a final blind validation step, MALDI-TOF-MS exhibited 88.9% sensitivity and 93.75% specificity for the detection of B. crocidurae in 50 O. sonrai ticks, including 18 that tested positive for B. crocidurae by PCR-sequencing. MALDI-TOF-MS took 45 minutes to be completed.Conclusions/SignificanceAfter the development of an appropriate database, MALDI-TOF-MS can be used to identify tick species and the presence of relapsing fever borreliae in a single assay. This work paves the way for the use of MALDI-TOF-MS for the dual identification of vectors and vectorized pathogens.
Highlights
The genus Borrelia is composed of bacterial pathogens responsible for relapsing fever and Lyme borreliosis [1]
Whereas the Lyme disease agents Borrelia burgdorferi [2], Borrelia garinii [3], Borrelia afzelii [4] and Borrelia valaisiana [5] are transmitted by hard ticks, the relapsing fever borreliae are transmitted by soft ticks [6,7] and lice [8]
Author Summary In Africa, relapsing fever borreliae are neglected vectorborne infections that cause mild to deadly septicemia and miscarriage
Summary
The genus Borrelia is composed of bacterial pathogens responsible for relapsing fever and Lyme borreliosis [1]. In Africa, four cultured species, Borrelia crocidurae, Borrelia duttonii, Borrelia recurrentis and Borrelia hispanica, and several not-yet cultured species are circulating in vector populations [1]. Screening vectors for these relapsing fever borreliae currently requires the use of technically demanding, timeand resource-consuming molecular methods [9,10]. Screening vectors for the presence of borreliae currently requires technically demanding, time- and resource-consuming molecular methods. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has recently emerged as a tool for the rapid identification of vectors and the identification of cultured borreliae. We investigated whether MALDI-TOF-MS could detect relapsing fever borreliae directly in ticks
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