[Cyclic rotation of antibiotics. Is all that glitters gold?]

Antibiotic cycling refers to the rotation of antimicrobial agents; that is, one specific agent or class of agents is withdrawn from use during a predefined time period, switched to another, and reintroduced at a later time. This strategy of periodic restriction attempts to reduce the selective pressure that antibiotic agents exert on microbial flora, thereby reducing antimicrobial resistance. Such control of antibiotic use has been proposed as an effective measure for preventing the emergence and spread of resistant pathogens, particularly in areas with high levels of antibiotic pressure. Although the first works on antibiotic cycling were published more than two decades ago, the experience with rotational therapy is limited. Most studies on this subject report intriguing and promising results. Nevertheless, a detailed examination of the literature discloses differences in the objectives proposed, the variables analyzed, and the methods for quantification, making generalization of the results difficult. The association between antibiotic use and emergence of multi-drug resistant pathogens has been extensively demonstrated, but the influence of several factors on the mechanisms of emergence and spread of antibiotic resistance in microorganisms makes it difficult to establish a cause-effect relationship. In this article several methodological considerations are suggested for future studies testing this new antibiotic strategy.