Vet. Res. 37 (2006) 145-154
DOI: 10.1051/vetres:2005046

Persistence of Mycoplasma synoviae in hens after two enrofloxacin treatments and detection of mutations in the parC gene

Jérôme Le Carrou, Anita K. Reinhardt, Isabelle Kempf and Anne V. Gautier-Bouchardon

Agence Française de Sécurité Sanitaire des Aliments, Laboratoire d'Études et de Recherches Avicoles et Porcines, Unité de Mycoplasmologie-Bactériologie, BP 53, 22440 Ploufragan, France

(Received 11 April 2005; accepted 12 July 2005; published online 13 December 2005)

Abstract - The ability of Mycoplasma synoviae, an avian pathogen, to persist despite fluoroquinolone treatments was investigated in hens. Groups of Mycoplasma-free hens were experimentally infected with the M. synoviae 317 strain and treated twice with enrofloxacin at the therapeutic dose. The results show that the two treatments did not have any influence on this strain of M. synoviae recovery from tracheal swabs. Mycoplasmas were isolated from tracheal swab cultures, but not from inner organs such as the liver or spleen, suggesting that this strain of M. synoviae was not able to cross the mucosal barrier to disseminate throughout the host. A significant increase of the resistance level to enrofloxacin of five re-isolated mycoplasma clones, was observed after the second treatment. This increase was associated in two clones to a Ser81->Pro substitution, found in the ParC quinolone-resistance determining region (QRDR) of DNA topoisomerase IV. This is the first time that a mutation in a gene coding for topoisomerase IV is described in M. synoviae after in vivo enrofloxacin treatments in experimentally infected hens.

Key words: Mycoplasma synoviae / fluoroquinolone / persistence / topoisomerase / poultry

Corresponding author: Anne V. Gautier-Bouchardon a.bouchardon@ploufragan.afssa.fr

© INRA, EDP Sciences 2005