Introduction
Evolving bacterial resistance to antimicrobial agents, one of the ten most critical public health threats according to the World Health Organization, demands immediate action[1]. Antimicrobial cycling or rotation is among the multitude of initiatives tried to streamline antibiotic prescribing, and fall within the umbrella term of antimicrobial stewardship. Cycling or rotation incurs scheduled shifts in empirical antibiotic treatment protocols, switching periodically between antimicrobial agents of similar spectrum. This practice is often adopted in high-risk settings such as Intensive Care Units and relies more or less on an intuitive perception that such scheduled rotations of antimicrobial agents could alter selective pressures on bacterial populations accordingly and thus stem the onset of resistant strains. The concept was probably further developed in the 90’s when Gerding et al reported improvements in aminoglycoside resistance rates as a result of changes in the type of predominant aminoglycoside use[2][3].
However, mathematical models have challenged the strategy’s presumable effectiveness by predicting that interventions which favoured a more heterogeneous antimicrobial use would be more successful in bacterial resistance control[4][5][6]. According to a 2006 systematic literature review very few studies met inclusion criteria and lack of rigorousness in study designs for those finally included was insufficient to draw safe inferences[7] A meta-analysis following almost ten years later suggested potential benefits by the application of the particular strategy without, however, performing an in-depth evaluation of the available studies[8].
We aim to provide an updated review and evaluation of the evidence with regard to the efficacy of antimicrobial cycling on bacterial resistance control within hospital settings. Our study is a composite element of a wider project with the objective to assess the impact of different antimicrobial stewardship initiatives on bacterial resistance rates which has led to the publication of two additional papers discussing the role of antimicrobial restrictions[9] and prospective audit with feedback[10].