title: Evaluation of in vitro susceptibility testing criteria for gemifloxacin when tested against Haemophilus influenzae strains with reduced susceptibility to ciprofloxacin and ofloxacin.
abstract: Although Hemophilus influenzae resistance to fluoroquinolones is low, it is important to monitor the development of populations with decreased susceptibility to this class of antimicrobials. The activity of gemifloxacin, a new fluoroquinolone, was measured against a collection of susceptible wild-type strains (MIC(90,) 0.008 microg/ml for both beta-lactamase-negative and -positive strains) and strains less susceptible to quinolones (MIC(90,) 1 microg/ml). Using a 5microg disk, the gemifloxacin-susceptible strains had MIC results ranging from </= 0.004 to 0.25 microg/ml (the proposed breakpoint), corresponding to zone diameters of 20 to 39 mm. However, some H. influenzae strains having multiple QRDR mutations were less susceptible to gemifloxacin (MIC range, 0.016-2 microg/ml), although gemifloxacin remained active against 57.1% of strains. In vitro testing, using these selected resistant strains, defined the categorical interpretive criteria for routine clinical laboratory use.
authors.affiliation: The JONES Group/JMI Laboratories, North Liberty, IA, USA. douglas-biedenbach@jmilabs.com
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Biedenbach
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Jones
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D024841:Fluoroquinolones; D000077735:Gemifloxacin; D006193:Haemophilus influenzae / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards; D009287:Naphthyridines / Q000494:pharmacology*; D015242:Ofloxacin / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D009287:Naphthyridines; D002939:Ciprofloxacin; D015242:Ofloxacin; D000077735:Gemifloxacin