Fluoroquinolone-resistant mutants obtained in vitro

Francisco García Lázaro (1) , R. Elisa Rodríguez-Tarazona (1) , José Ángel García-Rodríguez (1, 2) , Juan Luis Muñoz-Bellido (1, 2)

1 Departamento de Microbiología
2 Departamento de Medicina Preventiva

Three fluoroquinolone-resistant mutants were obtained after successive passages on norfloxacin-containing agar plates. The original strain was biovar 2 ATCC 23457. Mutants emerged at frequencies ranging between 1×10 and 3×10. The three mutants showed a Ala71→Ser mutation as well as insertion of Ala340. No mutations were observed in the and genes. Minimum inhibitory concentrations (MICs) increased by four- to eight-fold from the wild-type to the first-step mutant for norfloxacin, ciprofloxacin, levofloxacin and moxifloxacin. MICs of the second-step mutant increased significantly only for norfloxacin and those for the third-step mutant for norfloxacin and ciprofloxacin, suggesting the involvement of some efflux mechanism.

Mots clés: Fluoroquinolone

Francisco García Lázaro, R. Elisa Rodríguez-Tarazona, José Ángel García-Rodríguez, Juan Luis Muñoz-Bellido. Fluoroquinolone-resistant mutants obtained in vitro. International Journal of Antimicrobial Agents, 2009, 34 (3), pp.252. ⟨10.1016/j.ijantimicag.2008.12.013⟩. ⟨hal-00556325⟩