Use of fluoroquinolones in Intensive Care Units in a multi-drug-resistance era

Despite the high level of antibiotic resistance in ICUs, fluoroquinolones remain the most frequent utilized antibiotic in these settings. Since the discovery of this class of antibiotics several mechanisms have been identified as being responsible for resistance to fluoroquinolones; more recently attention has focused on a new mechanism which is responsible for transferable resistance, acting by means of enzymatic inactivation affecting only some members of the fluoroquinolone class. Indeed, the cr variant of the gene aac(6)-Ib translates an aminoglycoside acetyltransferase which confers reduced susceptibility to fluoroquinolones carrying this substrate, such as ciprofloxacin and norfloxacin, but not to others such as levofloxacin. It is therefore interesting to speculate that the use of levofloxacin could avoid the development of resistance in those bacteria presenting this enzyme but not in those carrying a Qnr gene. Application of these new aspects of molecular biology to clinical practice together with knowledge of the risk factors could in the future contribute to reduce the development of antibiotic resistance. ID consultation, the use of practical and reliable guidelines, the use of antibiotic association based on local epidemiology would represent further strategies to minimize antibiotic resistance development by optimizing the therapeutic choice.