Antimicrobial cycling programs

Because of increasing antimicrobial resistance in hospitals, antimicrobial cycling programs have been introduced in an effort to decrease rates of antimicrobial resistance (1-4). By limiting the exposure of bacteria to a certain class of antimicrobials, the development of resistance to the same class of antimicrobials may be delayed or avoided. Unfortunately, despite several studies having been reported in the literature (5-19), it is still unclear if antimicrobial cycling prevents the development of resistance. Aside from conflicting study results, the variability in the study design and the duration of each antimicrobial cycle has made comparisons of the studies difficult. The majority of published studies also relied on clinical culture results instead of surveillance culture results for assessing outcomes. Clinical culture results may not accurately reflect the development of resistance among bacterial pathogens since they only represent a small minority of bacteria within a patient population. Mathematical modeling studies have also favored antimicrobial mixing strategies over antimicrobial cycling (20,21). Finally, because of increasing fluoroquinolone resistance among Gram-negative bacilli (22,23), there may not be enough feasible cycling regimens available to provide the antimicrobial heterogeneity necessary for an effective antimicrobial cycling program.