naa a22 4500 555244180 20190205064557.0 cr unu---uuuuu 190205s2019 xx s 000 0 eng 0305-7453 10.1093/jac/dky402 doi (EDOC)oai:edoc.unibas.ch:68200 30295746 pmid Novel high-throughput screening method using quantitative PCR to determine the antimicrobial susceptibility of Orientia tsutsugamushi clinical isolates [Elektronische Daten] [Weerawat Phuklia, Phonepasith Panyanivong, Davanh Sengdetka, Piengchan Sonthayanon, Paul N. Newton, Daniel H. Paris, Nicholas P. J. Day, Sabine Dittrich] 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. Phuklia Weerawat joint author Panyanivong Phonepasith joint author Sengdetka Davanh joint author Sonthayanon Piengchan joint author Newton Paul N. joint author Paris Daniel H. joint author Day Nicholas P. J. joint author Dittrich Sabine joint author The journal of antimicrobial chemotherapy 74 (1), pp. 74-81 0305-7453 https://edoc.unibas.ch/68200/1/20190110145006_5c374d8ec85d1.pdf text/html WWW-Backlink auf das Repository 1 Article edoc PeerReviewed edoc peerstatus EDOC 856 40 https://edoc.unibas.ch/68200/1/20190110145006_5c374d8ec85d1.pdf text/html WWW-Backlink auf das Repository EDOC 700 1- Phuklia Weerawat joint author EDOC 700 1- Panyanivong Phonepasith joint author EDOC 700 1- Sengdetka Davanh joint author EDOC 700 1- Sonthayanon Piengchan joint author EDOC 700 1- Newton Paul N. joint author EDOC 700 1- Paris Daniel H. joint author EDOC 700 1- Day Nicholas P. J. joint author EDOC 700 1- Dittrich Sabine joint author EDOC 773 0- The journal of antimicrobial chemotherapy 74 (1), pp. 74-81 0305-7453 BK010053 XK010053 XK010000 EDOC EDOC EDOC Article