A major consideration for evaluating cycling strategies has come from work done by the pharmacokinetics group in Buffalo. Clearly variables other than simply the choice of antimicrobial affect clinical outcome and possibly the selective pressure for resistance. Nevertheless, the current expertise in hospital molecular epidemiology could serve these studies well. Government and industry should recognize the unique opportunity to cooperate in funding such studies. It is encouraging that the Centers for Disease Control and Prevention recently issued a request for applications to fund at least two new cycling initiatives.
Caution is needed in designing and implementing future antibiotic-cycling studies.
Previously published mathematical projections of the effectiveness of cycling reached pessimistic conclusions, albeit for infections that had no lasting colonization of the host. Indeed, McGowan, who has studied the epidemiology of antimicrobial resistance for over 30 years, warns of practical pitfalls. 24 Industry itself remains ambivalent about cycling, for, as Lavin has noted, new antimicrobials may have a relatively short or nonprofitable lifespan. Perhaps the greatest threat to antibiotic cycling involves the acquisition and assembly of resistance genes in nosocomial pathogens. 25 Promiscuous transposons contain recombinational hot spots for insertion of integrons containing gene cassettes.