[In vitro generation of mutants of Klebsiella pneumoniae following exposure to fluorquinolones. Relationship with the presence of extended spectrum betalactamases].

In order to provide data that may help to explain the relationship between production of extended spectrum betalactamases and fluorquinolone resistance in Klebsiella pneumoniae, we have developed an in vitro model of exposure to sub-inhibitory concentrations of various fluorquinolones (ciprofloxacin, levofloxacin and moxifloxacin) in two strains, one of which is a producer of extended spectrum betalactamases (ESBL). Our data show that mutants with reduced fluorquinolone susceptibility appear in both cases, but that they appear earlier in ESBL-producing strains (13.3 days versus 14.4 days), especially following exposure to ciprofloxacin (12.5 days versus 14.9 days for levofloxacin and 14.2 days for moxifloxacin). Therefore, our data help explain the greater fluorquinolone resistance in ESBL-producing strains and confirm the need to administer the correct doses of fluoroquinolones, especially in the case of ciprofloxacin, in order to prevent the emergence of resistant mutants. This is particularly important if the strain is an ESBL-producer.