Intrinsic fluoroquinolone resistance in Orientia tsutsugamushi

Wiwit Tantibhedhyangkul (1) , Emmanouil Angelakis (1) , Narongchai Tongyoo (2) , Paul N. Newton (2, 3) , Catrin E. Moore (2, 3) , Rattanaphone Phetsouvanh (2, 3) , Didier Raoult (1) , Jean-Marc Rolain (1)

1 Université de la Méditerranée - Aix-Marseille 2
2 Mahosot Hospital
3 AOPP - Department of Atmospheric, Oceanic and Planetary Physics [Oxford]

Scrub typhus is a public health concern for a population of over a billion humans, with an estimated incidence of one million cases/year in endemic areas. Although doxycycline remains the standard therapy, fluoroquinolones have been used successfully in a few patients. However, there is also clinical evidence that fluoroquinolones are ineffective in the treatment of scrub typhus. To clarify this matter, we determined the in vitro susceptibility of strain Kato to ciprofloxacin and sequenced the quinolone resistance-determining region (QRDR) of the gene, the target of fluoroquinolones, of 18 fresh isolates from Lao PDR. strain Kato was resistant to ciprofloxacin and ofloxacin in vitro (minimum inhibitory concentration=8μg/mL). All sequences obtained, including those from the two available genomes of (strains Boryong and Ikeda), had a Ser83Leu mutation in their QRDR domain that is known to be associated with fluoroquinolone resistance. These findings re-emphasise the usefulness of in silico analysis for the prediction of antibiotic resistance and suggest that fluoroquinolones should not be used in the treatment of scrub typhus.

Mots clés: Scrub typhus; Fluoroquinolone resistance; DNA gyrase; Laos

Wiwit Tantibhedhyangkul, Emmanouil Angelakis, Narongchai Tongyoo, Paul N. Newton, Catrin E. Moore, et al.. Intrinsic fluoroquinolone resistance in Orientia tsutsugamushi. International Journal of Antimicrobial Agents, 2010, 35 (4), pp.338. ⟨10.1016/j.ijantimicag.2009.11.019⟩. ⟨hal-00567280⟩