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Novel high-throughput screening method using quantitative PCR to determine the antimicrobial susceptibility of Orientia tsutsugamushi clinical isolates

Phuklia, Weerawat and Panyanivong, Phonepasith and Sengdetka, Davanh and Sonthayanon, Piengchan and Newton, Paul N. and Paris, Daniel H. and Day, Nicholas P. J. and Dittrich, Sabine. (2019) Novel high-throughput screening method using quantitative PCR to determine the antimicrobial susceptibility of Orientia tsutsugamushi clinical isolates. The journal of antimicrobial chemotherapy, 74 (1). pp. 74-81.

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Official URL: https://edoc.unibas.ch/68200/

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Abstract

To develop a method to enable the large-scale antimicrobial susceptibility screening of Orientia tsutsugamushi clinical isolates, using one timepoint and one concentration of antibiotics to considerably speed up the time to result.; Growth, harvesting, multiplicity of infection (moi) and the day to determine the MICs were optimized using five O. tsutsugamushi reference strains [susceptible (Karp, Kato and Gilliam) and putatively resistant (AFC-3 and AFSC-4)], one clinical isolate (UT76) and one rodent isolate (TA763). Subsequently, the MICs of azithromycin, chloramphenicol and doxycycline for these strains and 51 clinical isolates including AFSC-7 were determined. An optimal concentration was calculated using the epidemiological cut-off value.; The conditions for O. tsutsugamushi infection, growth and harvesting were determined to be an moi of 100:1 and trypsinization with the peak growth on day 10. The resulting MICs were in line with previously published susceptibility data for all reference strains, except for Karp and AFSC-4, which showed azithromycin MICs of 0.0156 and 0.0313 mg/L, compared with 0.0078 and 0.0156 mg/L, respectively, in previous reports. The MIC of doxycycline for AFC-3 was 0.125 mg/L compared with >4 mg/L in earlier reports. The final single screening concentrations were identified as: azithromycin, 0.125 mg/L; chloramphenicol, 8 mg/L; and doxycycline, 1 mg/L.; This simplified procedure facilitates the simultaneous screening of 48 isolates for actively monitoring potential resistance of this important fever pathogen, with an 8-fold throughput improvement over early methods. The data do not support the existence of doxycycline- and chloramphenicol-resistant scrub typhus.
Faculties and Departments:09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Medicine (MED)
UniBasel Contributors:Paris, Daniel Henry
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Oxford University Press
ISSN:0305-7453
e-ISSN:1460-2091
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
Last Modified:04 Feb 2019 13:59
Deposited On:04 Feb 2019 13:57

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